Microchip Technology Curiosity Nano PIC24FJ64GU205 User manual

PIC24FJ64GU205 Curiosity Development Board Nano
User's Guide
Preface
The PIC24FJ64GU205 Curiosity Nano evaluation kit is a hardware platform to evaluate microcontrollers in the
PIC24FJGU205 family. This board has the PIC24FJ64GU205 microcontroller (MCU) mounted.
Supported by MPLAB® X IDE , the board provides easy access to the features of the PIC24FJ64GU205 to explore
how to integrate the device into a custom design.
The Curiosity Nano series of evaluation boards include an on-board debugger. No external tools are necessary to
program and debug the PIC24FJ64GU205.
•MPLAB® X IDE - Software to discover, configure, develop, program, and debug Microchip microcontrollers.
•Code examples - Get started with code examples.
•PIC24FJ64GU205 website - Find documentation, data sheets, sample, and purchase microcontrollers.
•PIC24FJ64GU205 Curiosity Nano website - Kit information, latest user guide, and design documentation.
© 2021 Microchip Technology Inc. User Guide 50003124A-page 1

Table of Contents
Preface........................................................................................................................................................... 1
1. Introduction............................................................................................................................................. 4
1.1. Features....................................................................................................................................... 4
1.2. Board Overview............................................................................................................................4
2. Getting Started........................................................................................................................................ 5
2.1. Quick Start....................................................................................................................................5
2.1.1. Driver Installation...........................................................................................................5
2.1.2. Kit Window.....................................................................................................................5
2.1.3. MPLAB® X IDE Device Family Packs............................................................................5
2.2. Design Documentation and Relevant Links................................................................................. 5
3. Curiosity Nano.........................................................................................................................................7
3.1. On-Board Debugger Overview..................................................................................................... 7
3.1.1. Debugger.......................................................................................................................7
3.1.2. Virtual Serial Port (CDC)................................................................................................8
3.1.2.1. Overview..................................................................................................... 8
3.1.2.2. Operating System Support.......................................................................... 8
3.1.2.3. Limitations................................................................................................... 9
3.1.2.4. Signaling......................................................................................................9
3.1.2.5. Advanced Use........................................................................................... 10
3.1.3. Mass Storage Device...................................................................................................10
3.1.3.1. Mass Storage Device Implementation.......................................................11
3.1.3.2. Configuration Words..................................................................................11
3.1.3.3. Special Commands................................................................................... 11
3.1.4. Data Gateway Interface (DGI)..................................................................................... 12
3.1.4.1. Debug GPIO..............................................................................................12
3.1.4.2. Timestamping............................................................................................ 13
3.2. Curiosity Nano Standard Pinout................................................................................................. 13
3.3. Power Supply............................................................................................................................. 14
3.3.1. Target Regulator.......................................................................................................... 15
3.3.2. External Supply............................................................................................................16
3.3.3. VBUS Output Pin.........................................................................................................16
3.3.4. Power Supply Exceptions............................................................................................17
3.4. Low-Power Measurement.......................................................................................................... 18
3.5. Programming External Microcontrollers..................................................................................... 19
3.5.1. Supported Devices...................................................................................................... 19
3.5.2. Software Configuration................................................................................................ 19
3.5.3. Hardware Modifications............................................................................................... 20
3.5.4. Connecting to External Microcontrollers...................................................................... 21
3.6. Connecting External Debuggers................................................................................................ 22
4. Hardware User Guide........................................................................................................................... 24
4.1. Connectors.................................................................................................................................24
4.1.1. PIC24FJ64GU205 Curiosity Nano Pinout....................................................................24
© 2021 Microchip Technology Inc. User Guide 50003124A-page 2

4.1.2. Using Pin-Headers.......................................................................................................24
4.2. Peripherals................................................................................................................................. 25
4.2.1. Target USB Connector.................................................................................................25
4.2.2. LED..............................................................................................................................25
4.2.3. Mechanical Switch.......................................................................................................26
4.2.4. Crystal..........................................................................................................................26
4.2.5. Target USB Connector.................................................................................................27
4.2.6. On-Board Debugger Implementation...........................................................................27
4.2.6.1. On-Board Debugger Connections............................................................. 27
5. Hardware Revision History and Known Issues..................................................................................... 28
5.1. Identifying Product ID and Revision........................................................................................... 28
6. Document Revision History...................................................................................................................29
7. Appendix............................................................................................................................................... 30
7.1. Schematic...................................................................................................................................30
7.2. Assembly Drawing......................................................................................................................32
7.3. Curiosity Nano Base for Click boards™...................................................................................... 33
7.4. Disconnecting the On-Board Debugger..................................................................................... 34
The Microchip Website.................................................................................................................................36
Product Change Notification Service............................................................................................................36
Customer Support........................................................................................................................................ 36
Microchip Devices Code Protection Feature................................................................................................ 36
Legal Notice................................................................................................................................................. 37
Trademarks.................................................................................................................................................. 37
Quality Management System....................................................................................................................... 38
Worldwide Sales and Service.......................................................................................................................39
© 2021 Microchip Technology Inc. User Guide 50003124A-page 3

1. Introduction
1.1 Features
• PIC24FJ64GU205 Microcontroller
• One Yellow User LED
• One Mechanical User Switch
• Footprint for 32.768 kHz Crystal
• Micro-USB connector to develop USB Device application using the integrated USB peripheral on the
PIC24FJ64GU205
• On-Board Debugger:
– Board identification in Microchip MPLAB® X IDE
– One green power and status LED
– Programming and debugging
– Virtual serial port (CDC)
– One debug GPIO channel (DGI GPIO)
• USB Powered
• Adjustable Target Voltage:
– MIC5353 LDO regulator controlled by the on-board debugger
– 1.8-3.6V output voltage (limited by USB input voltage)
– 500 mA maximum output current (limited by ambient temperature and output voltage)
1.2 Board Overview
The Microchip PIC24FJ64GU205 Curiosity Nano evaluation kit is a hardware platform to evaluate the
PIC24FJ64GU205 microcontroller.
Figure 1-1. PIC24FJ64GU205 Curiosity Nano Board Overview
User Switch
(SW0)
User LED
(LED0)
PIC24FJ64GU205
MCU
32.768 kHz
Crystal Footprint
Debugger
Power/Status
LED
Micro USB
Program/Debug
Micro USB PIC
User Device Port
Introduction
© 2021 Microchip Technology Inc. User Guide 50003124A-page 4

2. Getting Started
2.1 Quick Start
Steps to start exploring the PIC24FJ64GU205 Curiosity Nano board:
1. Download Microchip MPLAB® X IDE.
2. Download MPLAB® XC C Compiler.
3. Launch MPLAB® X IDE.
4. Optional: Use MPLAB® Code Configurator to generate drivers and examples.
5. Write the application code.
6. Connect a USB cable (Standard-A to Micro-B or Micro-AB) between the PC and the debug USB port on the
board.
2.1.1 Driver Installation
When the board connects to the computer for the first time, the operating system will perform a driver software
installation. The driver file supports both 32- and 64-bit versions of Microsoft® Windows® XP, Windows Vista®,
Windows® 7, Windows® 8, and Windows® 10. The drivers for the board are included with MPLAB® X IDE.
2.1.2 Kit Window
Once the board is powered, the green status LED will lit, and MPLAB® X IDE will auto-detect which boards
are connected. The Kit Window in MPLAB® X IDE will present relevant information like data sheets and board
documentation. The PIC24FJ64GU205 device on the PIC24FJ64GU205 Curiosity Nano board is programmed and
debugged by the on-board debugger and, therefore, no external programmer or debugger tool is required.
Tip: If closed, the Kit Window in MPLAB® X IDE can be reopened through the menu bar Window > Kit
Window.
2.1.3 MPLAB® X IDE Device Family Packs
Microchip MPLAB® X IDE requires specific information to support devices and tools. This information is contained
in versioned packs. For the PIC24FJ64GU205 Curiosity Nano board, Microchip MPLAB® X IDE version 5.45 with
device family pack "PICxx" version x.y.z and tool pack "nEDBG_TP" version x.y.z or newer are required. For more
information on packs and how to upgrade them, refer to the MPLAB® X IDE User’s guide - Work with Device Packs.
Tip: The latest device family packs are available through Tools > Packs in MPLAB® X IDE or online at
Microchip MPLAB® X Packs Repository.
2.2 Design Documentation and Relevant Links
The following list contains links to the most relevant documents and software for the PIC24FJ64GU205 Curiosity
Nano board:
•MPLAB® X IDE - MPLAB X IDE is a software program that runs on a PC (Windows®, Mac OS®, Linux®)
to develop applications for Microchip microcontrollers and digital signal controllers. It is named an Integrated
Development Environment (IDE) because it provides a single integrated “environment” to develop code for
embedded microcontrollers.
Getting Started
© 2021 Microchip Technology Inc. User Guide 50003124A-page 5

•MPLAB® XC Compilers - MPLAB® XC16 C Compiler is available as a free, unrestricted-use download.
Microchips MPLAB® XC16 C Compiler is a comprehensive solution for your project’s software development
on Windows®, macOS® or Linux®. MPLAB® XC16 supports all 16-bit PIC® MCUs and dsPIC® Digital Signal
Controllers (DSCs).
•MPLAB® Code Configurator - MPLAB Code Configurator (MCC) is a free software plug-in that provides a
graphical interface to configure peripherals and functions specific to your application.
•Microchip Sample Store - Microchip sample store where you can order samples of devices.
•MPLAB Data Visualizer - MPLAB Data Visualizer is a program used for processing and visualizing data. The
Data Visualizer can receive data from various sources such as serial ports and on-board debugger’s Data
Gateway Interface, as found on Curiosity Nano and Xplained Pro boards.
•Microchip PIC® and AVR® Examples - Microchip PIC and AVR Device Examples is a collection of examples
and labs that use Microchip development boards to showcase the use of PIC and AVR device peripherals.
•Microchip PIC® and AVR® Solutions - Microchip PIC and AVR Device Solutions contains complete
applications for use with Microchip development boards, ready to be adapted and extended.
•PIC24FJ64GU205 Curiosity Nano website - Kit information, latest user guide, and design documentation.
•PIC24FJ64GU205 Curiosity Nano on Microchip Direct - Purchase this kit on Microchip Direct.
Getting Started
© 2021 Microchip Technology Inc. User Guide 50003124A-page 6

3. Curiosity Nano
Curiosity Nano is an evaluation platform of small boards with access to most of the microcontrollers I/Os. The
platform consists of a series of low pin count microcontroller (MCU) boards with on-board debuggers, which
integrates with MPLAB® X IDE. Each board is identified in the IDE. When plugged in, a Kit Window is displayed
with links to key documentation, including relevant user guides, application notes, data sheets, and example code.
Everything is easy to find. The on-board debugger features a virtual serial port (CDC) for serial communication to a
host PC and a Data Gateway Interface (DGI) with debug GPIO pin(s).
3.1 On-Board Debugger Overview
PIC24FJ64GU205 Curiosity Nano contains an on-board debugger for programming and debugging. The on-board
debugger is a composite USB device consisting of several interfaces:
• A debugger that can program and debug the PIC24FJ64GU205 in MPLAB® X IDE
• A mass storage device that allows drag-and-drop programming of the PIC24FJ64GU205
• A virtual serial port (CDC) that is connected to a Universal Asynchronous Receiver/Transmitter (UART) on
the PIC24FJ64GU205, and provides an easy way to communicate with the target application through terminal
software
• A Data Gateway Interface (DGI) for code instrumentation with logic analyzer channels (debug GPIO) to visualize
program flow
The on-board debugger controls a Power and Status LED (marked PS) on the PIC24FJ64GU205 Curiosity Nano
board. The table below shows how the LED is controlled in different operation modes.
Table 3-1. On-Board Debugger LED Control
Operation Mode Power and Status LED
Boot Loader mode The LED blinks slowly during power-up
Power-up The LED is ON
Normal operation The LED is ON
Programming Activity indicator: The LED blinks slowly during programming/debugging
Drag-and-drop
programming Success: The LED blinks slowly for 2 sec.
Failure: The LED blinks rapidly for 2 sec.
Fault The LED blinks rapidly if a power fault is detected
Sleep/Off The LED is OFF. The on-board debugger is either in a sleep mode or powered down.
This can occur if the board is externally powered.
Info: Slow blinking is approximately 1 Hz, and rapid blinking is approximately 5 Hz.
3.1.1 Debugger
The on-board debugger on the PIC24FJ64GU205 Curiosity Nano board appears as a Human Interface Device (HID)
on the host computer’s USB subsystem. The debugger supports full-featured programming and debugging of the
PIC24FJ64GU205 using MPLAB® X IDE.
Curiosity Nano
© 2021 Microchip Technology Inc. User Guide 50003124A-page 7

Remember: Keep the debugger’s firmware up-to-date. Firmware upgrades automatically when using
MPLAB® X IDE.
3.1.2 Virtual Serial Port (CDC)
The virtual serial port (CDC) is a general purpose serial bridge between a host PC and a target device.
3.1.2.1 Overview
The on-board debugger implements a composite USB device that includes a standard Communications Device Class
(CDC) interface, which appears on the host as a virtual serial port. The CDC can be used to stream arbitrary data
in both directions between the host computer and the target: All characters sent through the virtual serial port on the
host computer will be transmitted as UART on the debugger’s CDC TX pin, and UART characters captured on the
debugger’s CDC RX pin will be returned to the host computer through the virtual serial port.
Figure 3-1. CDC Connection
Target MCU
UART TX
UART RX
Debugger
USB
CDC RX
CDC TX
PC
Terminal
Software
Target
Receive
Target
Send
Terminal
Receive
Terminal
Send
Info: As shown in Figure 3-1, the debugger’s CDC TX pin is connected to a UART RX pin on the target
for receiving characters from the host computer. Similarly, the debugger’s CDC RX pin is connected to a
UART TX pin on the target for transmitting characters to the host computer.
3.1.2.2 Operating System Support
On Windows® machines, the CDC will enumerate as Curiosity Virtual COM Port and appear in the Ports section of
the Windows Device Manager. The COM port number can also be found there.
Info: On older Windows systems, the CDC requires a USB. This driver is included in installations of
MPLAB® X IDE.
On Linux® machines, the CDC will enumerate and appear as /dev/ttyACM#.
Info: tty* devices belong to the “dialout” group in Linux, so it may be necessary to become a member of
that group to have permissions to access the CDC.
On Mac® machines, the CDC will enumerate and appear as /dev/tty.usbmodem#. Depending on which terminal
program is used, it will appear in the available list of modems as usbmodem#.
Curiosity Nano
© 2021 Microchip Technology Inc. User Guide 50003124A-page 8

Info: For all operating systems: Be sure to use a terminal emulator that supports DTR signaling. See
3.1.2.4 Signaling.
3.1.2.3 Limitations
Not all UART features are implemented in the on-board debugger CDC. The constraints are outlined here:
•Baud rate: Must be in the range of 1200 bps to 500 kbps. Any baud rate outside this range will be set to the
closest limit, without warning. Baud rate can be changed on-the-fly.
•Character format: Only 8-bit characters are supported.
•Parity: Can be odd, even, or none.
•Hardware flow control: Not supported.
•Stop bits: One or two bits are supported.
3.1.2.4 Signaling
During USB enumeration, the host OS will start both communication and data pipes of the CDC interface. At this
point, it is possible to set and read back the baud rate and other UART parameters of the CDC, but data sending and
receiving will not be enabled.
When a terminal connects to the host, it must assert the DTR signal. As this is a virtual control signal implemented
on the USB interface, it is not physically present on the board. Asserting the DTR signal from the host will indicate to
the on-board debugger that a CDC session is active. The debugger will then enable its level shifters (if available) and
start the CDC data send and receive mechanisms.
Deasserting DTR in debugger firmware version 1.20 or earlier has the following behavior:
• Debugger UART receiver is disabled, and no further data will be transferred to the host computer
• Debugger UART transmitter will continue to send data that is queued for sending, but no new data is accepted
from the host computer
• Level shifters (if available) are not disabled, and the debugger CDC TX line remains driven
Deasserting DTR in debugger firmware version 1.21 or later has the following behavior:
• Debugger UART receiver is disabled, so no further data will be transferred to the host computer
• Debugger UART transmitter will continue to send data that is queued for sending, but no new data is accepted
from the host computer
• Once the ongoing transmission is complete, level shifters (if available) are disabled, so the debugger CDC TX
line will become high-impedance
Remember: Set up the terminal emulator to assert the DTR signal. Without the signal, the on-board
debugger will not send or receive any data through its UART.
Tip: The on-board debugger’s CDC TX pin will not be driven until the CDC interface is enabled by the
host computer. Also, there are no external pull-up resistors on the CDC lines connecting the debugger and
the target, which means that during power-up, these lines are floating. To avoid any glitches resulting in
unpredictable behavior like framing errors, the target device may enable the internal pull-up resistor on the
pin connected to the debugger’s CDC TX pin.
Curiosity Nano
© 2021 Microchip Technology Inc. User Guide 50003124A-page 9

3.1.2.5 Advanced Use
CDC Override Mode
In normal operation, the on-board debugger is a true UART bridge between the host and the device. However, in
certain use cases, the on-board debugger can override the basic operating mode and use the CDC TX and RX pins
for other purposes.
Dropping a text file into the on-board debugger’s mass storage drive can be used to send characters out of the
debugger’s CDC TX pin. The filename and extension are trivial, but the text file must start with the characters:
CMD:SEND_UART=
Debugger firmware version 1.20 or earlier has the following limitations:
• The maximum message length is 50 characters – all remaining data in the frame are ignored
• The default baud rate used in this mode is 9600 bps, but if the CDC is already active or has been configured,
the previously used baud rate still applies
Debugger firmware version 1.21 and later has the following limitations/features:
• The maximum message length may vary depending on the MSC/SCSI layer timeouts on the host computer
and/or operating system. A single SCSI frame of 512 bytes (498 characters of payload) is ensured, and files of
up to 4 KB will work on most systems. The transfer will complete on the first NULL character encountered in the
file.
• The baud rate used is always 9600 bps for the default command:
CMD:SEND_UART=
• Do not use the CDC override mode simultaneously with data transfer over the CDC/terminal. If a CDC terminal
session is active at the time a file is received via CDC override mode, it will be suspended for the duration of the
operation and resumed once complete.
• Additional commands are supported with explicit baud rates:
CMD:SEND_9600=
CMD:SEND_115200=
CMD:SEND_460800=
USB-Level Framing Considerations
Sending data from the host to the CDC can be done byte-wise or in blocks, which will be chunked into 64-byte USB
frames. Each such frame will be queued up for sending to the debugger’s CDC TX pin. Transferring a small amount
of data per frame can be inefficient, particularly at low baud rates, as the on-board debugger buffers frames and not
bytes. A maximum of four 64-byte frames can be active at any time. The on-board debugger will throttle the incoming
frames accordingly. Sending full 64-byte frames containing data is the most efficient method.
When receiving data on the debugger’s CDC RX pin, the on-board debugger will queue up the incoming bytes into
64-byte frames, which are sent to the USB queue for transmission to the host when they are full. Incomplete frames
are also pushed to the USB queue at approximately 100 ms intervals, triggered by USB start-of-frame tokens. Up to
eight 64-byte frames can be active at any time.
If the host (or the software running on it) fails to receive data fast enough, an overrun will occur. When this happens,
the last-filled buffer frame will be recycled instead of being sent to the USB queue, and a full data frame will be lost.
To prevent this occurrence, the user must ensure that the CDC data pipe is being read continuously, or the incoming
data rate must be reduced.
3.1.3 Mass Storage Device
The on-board debugger includes a simple Mass Storage Device implementation, which is accessible for read/write
operations via the host operating system to which it is connected.
It provides:
• Read access to basic text and HTML files for detailed kit information and support
Curiosity Nano
© 2021 Microchip Technology Inc. User Guide 50003124A-page 10

• Write access for programming Intel® HEX formatted files into the target device’s memory
• Write access for simple text files for utility purposes
3.1.3.1 Mass Storage Device Implementation
The on-board debugger implements a highly optimized variant of the FAT12 file system that has several limitations,
partly due to the nature of FAT12 itself and optimizations made to fulfill its purpose for its embedded application.
The Curiosity Nano USB device is USB Chapter 9-compliant as a mass storage device but does not, in any way, fulfill
the expectations of a general purpose mass storage device. This behavior is intentional.
When using the Windows operating system, the on-board debugger enumerates as a Curiosity Nano USB Device
that can be found in the disk drives section of the device manager. The CURIOSITY drive appears in the file manager
and claims the next available drive letter in the system.
The CURIOSITY drive contains approximately one MB of free space, and this does not reflect the size of the
target device’s Flash in any way. When programming an Intel® HEX file, the binary data are encoded in ASCII with
metadata providing a large overhead, so one MB is a trivially chosen value for disk size.
It is not possible to format the CURIOSITY drive. When programming a file to the target, the filename may appear in
the disk directory listing. This is merely the operating system’s view of the directory, which has not been updated in
reality. It is not possible to read out the file contents. Removing and replugging the board will return the file system to
its original state, but the target will still contain the application that has previously been programmed.
To erase the target device, copy a text file starting with “CMD:ERASE” onto the disk.
By default, the CURIOSITY drive contains several read-only files for generating icons as well as reporting status and
linking to further information:
•AUTORUN.ICO – icon file for the Microchip logo
•AUTORUN.INF – system file required for Windows Explorer to show the icon file
•KIT-INFO.HTM – redirect to the development board website
•KIT-INFO.TXT – a text file containing details about the board’s debugger firmware version, board name, USB
serial number, device, and drag-and-drop support
•STATUS.TXT – a text file containing the programming status of the board
Info: STATUS.TXT is dynamically updated by the on-board debugger. The contents may be cached by
the OS and, therefore, do not reflect the correct status.
3.1.3.2 Configuration Words
Configuration Words (PIC® MCU Targets)
Configuration Word settings included in the project being programmed after program Flash is programmed. The
debugger will not mask out any bits in the Configuration Words when writing them, but since it uses Low-Voltage
Programming mode, it is unable to clear the LVP Configuration bit. If the incorrect clock source is selected,
for example, and the board does not boot, it is always possible to perform a bulk erase (always done before
programming) and restore the device to its default settings.
3.1.3.3 Special Commands
Several utility commands are supported by copying text files to the mass storage disk. The filename or extension is
irrelevant – the command handler reacts to content only.
Table 3-2. Special File Commands
Command Content Description
CMD:ERASE Executes a chip erase of the target
CMD:SEND_UART= Sends a string of characters to the CDC UART. See “CDC
Override Mode.”
Curiosity Nano
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...........continued
Command Content Description
CMD:SEND_9600=
CMD:SEND_115200=
CMD:SEND_460800=
Sends a string of characters to the CDC UART at the baud rate
specified. Note that only the baud rates explicitly specified here
are supported! See “CDC Override Mode”. (Debugger firmware
v1.21 or newer.)
CMD:RESET Resets the target device by entering Programming mode and
then exiting Programming mode immediately afterward. Exact
timing can vary according to the programming interface of the
target device. (Debugger firmware v1.16 or newer.)
CMD:POWERTOGGLE Powers down the target and restores power after a 100
ms delay. If external power is provided, this has no effect.
(Debugger firmware v1.16 or newer.)
CMD:0V Powers down the target device by disabling the target supply
regulator. If external power is provided, this has no effect.
(Debugger firmware v1.16 or newer.)
CMD:1V8 Sets the target voltage to 1.8V. If external power is provided,
this has no effect. (Debugger firmware v1.21 or newer.)
CMD:3V3 Sets the target voltage to 3.3V. If external power is provided,
this has no effect. (Debugger firmware v1.16 or newer.)
CMD:5V0 Sets the target voltage to 5.0V. If external power is provided,
this has no effect. (Debugger firmware v1.16 or newer.)
Info: The content sent to the mass storage emulated disk triggers the commands listed here and
provides no feedback in the case of either success or failure.
3.1.4 Data Gateway Interface (DGI)
Data Gateway Interface (DGI) is a USB interface for transporting raw and timestamped data between on-board
debuggers and host computer-based visualization tools. MPLAB Data Visualizer is used on the host computer to
display debug GPIO data. It is available as a plug-in for MPLAB® X IDE or a stand-alone application that can be used
in parallel with MPLAB® X IDE.
Although DGI encompasses several physical data interfaces, the PIC24FJ64GU205 Curiosity Nano implementation
includes logic analyzer channels:
• One debug GPIO channel (also known as DGI GPIO)
3.1.4.1 Debug GPIO
Debug GPIO channels are timestamped digital signal lines connecting the target application to a host computer
visualization application. They are typically used to plot the occurrence of low-frequency events on a time-axis – for
example, when certain application state transitions occur.
The figure below shows the monitoring of the digital state of a mechanical switch connected to a debug GPIO in
MPLAB Data Visualizer.
Curiosity Nano
© 2021 Microchip Technology Inc. User Guide 50003124A-page 12

Figure 3-2. Monitoring Debug GPIO with MPLAB® Data Visualizer
Debug GPIO channels are timestamped, so the resolution of DGI GPIO events is determined by the resolution of the
DGI timestamp module.
Important: Although bursts of higher frequency signals can be captured, the useful frequency range of
signals for which debug GPIO can be used is up to about 2 kHz. Attempting to capture signals above this
frequency will result in data saturation and overflow, which may cause the DGI session to be aborted.
3.1.4.2 Timestamping
DGI sources are timestamped as they are captured by the debugger. The timestamp counter implemented in the
Curiosity Nano debugger increments at 2 MHz frequency, providing a timestamp resolution of a half microsecond.
3.2 Curiosity Nano Standard Pinout
The 12 edge connections closest to the USB connector on Curiosity Nano boards have a standardized pinout. The
program/debug pins have different functions depending on the target programming interface, as shown in the table
and figure below.
Table 3-3. Curiosity Nano Standard Pinout
Debugger Signal Target MCU Description
ID — ID line for extensions
CDC TX UART RX USB CDC TX line
CDC RX UART TX USB CDC RX line
DBG0 ICSPDAT Debug data line
DBG1 ICSPCLK Debug clock line
DBG2 GPIO0 debug GPIO0
DBG3 MCLR Reset line
NC — No connect
Curiosity Nano
© 2021 Microchip Technology Inc. User Guide 50003124A-page 13

...........continued
Debugger Signal Target MCU Description
VBUS — VBUS voltage for external use
VOFF — Voltage Off input. Disables the target regulator and
target voltage when pulled low.
VTG — Target voltage
GND — Common ground
Figure 3-3. Curiosity Nano Standard Pinout
USB
DEBUGGER
PS LED
NC
ID
CDC RX
CDC TX
DBG1
DBG2
VBUS
VOFF
DBG3
DBG0
GND
VTG
CURIOSITY NANO
3.3 Power Supply
The board is powered through either of the USB ports and contains two LDO regulators, one to generate 3.3V for
the on-board debugger and an adjustable LDO regulator for the target PIC24FJ64GU205 microcontroller and its
peripherals. The voltage from a USB connector can vary between 4.4V to 5.25V (according to the USB specification)
and will limit the maximum voltage to the target. The figure below shows the entire power supply system on
PIC24FJ64GU205 Curiosity Nano.
Figure 3-4. Power Supply Block Diagram
Debugger
USB
Target
MCU
Power source
Cut strap
Power consumer P3V3 Debugger
Power converter
Debugger
Regulator
VUSB
Target
Regulator
Power
Supply
strap
Adjust
Level
shifter
VLVL
VREG
I/O I/O GPIO
straps
I/O
On/Off
Measure On/Off
PTC
Fuse
Power protection
Target
Power
strap
VTG
VBUS #VOFF ID system
Target
USB
Power
MUX
Curiosity Nano
© 2021 Microchip Technology Inc. User Guide 50003124A-page 14

Info: The power MUX allows the board to be powered by either USB port. If both USB power sources are
connected, the MUX will select the target USB port to power the board.
3.3.1 Target Regulator
The target voltage regulator is a MIC5353 variable output LDO. The on-board debugger can adjust the voltage output
supplied to the board target section by manipulating the MIC5353’s feedback voltage. The hardware implementation
is limited to an approximate voltage range from 1.7V to 5.1V. Additional output voltage limits are configured in the
debugger firmware to ensure that the output voltage never exceeds the hardware limits of the PIC24FJ64GU205
microcontroller. The voltage limits configured in the on-board debugger on PIC24FJ64GU205 Curiosity Nano are
2.0-3.6V.
Info: The target voltage is set to 3.3V when the board is manufactured. It can be changed through the
MPLAB® X IDE project properties. Any change to the target voltage is persistent, even after a power
toggle. The resolution is less than 5 mV but may be limited to 10 mV by the adjustment program.
Info: The voltage settings setup in MPLAB® X IDE are not immediately applied to the board. The new
voltage setting is applied to the board when the debugger is accessed in any way, like pushing the Refresh
Debug Tool Status button in the project dashboard tab or programming/reading program memory.
Info: There is a simple option to adjust the target voltage with a drag-and-drop command text file to
the board, which supports a set of common target voltages. See section 3.1.3.3 Special Commands for
further details.
The MIC5353 supports a maximum current load of 500 mA. It is an LDO regulator in a small package, placed on a
small printed circuit board (PCB), and the thermal shutdown condition can be reached at lower loads than 500 mA.
The maximum current load depends on the input voltage, the selected output voltage, and the ambient temperature.
The figure below shows the safe operating area for the regulator, with an input voltage of 5.1V and an ambient
temperature of 23°C.
Figure 3-5. Target Regulator Safe Operation Area
The voltage output of the target regulator is continuously monitored (measured) by the on-board debugger. If it is
more than 100 mV over/under the set device voltage, an error condition will be flagged, and the target voltage
regulator will be turned off. This will detect and handle any short-circuit conditions. It will also detect and handle if an
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external voltage, which causes VCC_TARGET to move outside of the voltage setting monitoring window of ±100 mV,
is suddenly applied to the VTG pin without setting the VOFF pin low.
Info: The on-board debugger has a monitoring window of VCC_TARGET±100 mV. If the external voltage
is under this limit, the on-board debugger status LED will blink rapidly. If the external voltage is above
this limit, the on-board debugger status LED will continue to shine. If the external voltage is removed, the
status LED will start to blink rapidly until the on-board debugger detects the new situation and turns the
target voltage regulator back on.
3.3.2 External Supply
An external voltage instead of the on-board target regulator can power the PIC24FJ64GU205 Curiosity Nano. When
the Voltage Off (VOFF) pin is shorted to ground (GND), the on-board debugger firmware disables the target regulator,
and it is safe to apply an external voltage to the VTG pin.
It is also safe to apply an external voltage to the VTG pin when no USB cable is plugged into the DEBUG connector
on the board.
The VOFF pin can be tied low/let go at any time. This will be detected by a pin-change interrupt to the on-board
debugger, which controls the target voltage regulator accordingly.
WARNING
Applying an external voltage to the VTG pin without shorting VOFF to GND may cause permanent damage
to the board.
WARNING
Do not apply any voltage to the VOFF pin. Let the pin float to enable the power supply.
WARNING
The absolute maximum external voltage is 5.5V for the on-board level shifters, and the standard operating
condition of the PIC24FJ64GU205 is 2.0-3.6V. Applying a higher voltage may cause permanent damage
to the board.
Info: If an external voltage is applied without pulling the VOFF pin low and an external supply pulls the
voltage lower than the monitoring window’s lower limit (target voltage setting – 100 mV), the on-board
debugger status LED will blink rapidly and shut the on-board regulator off. If an external voltage is
suddenly removed when the VOFF pin is not pulled low, the status LED will start to blink rapidly until the
on-board debugger detects the new situation and switches the target voltage regulator back on.
Programming, debugging, and data streaming is still possible with an external power supply – the debugger and
signal level shifters will be powered from the USB cable. Both regulators, the debugger, and the level shifters are
powered down when the USB cable is removed.
Info: In addition to the power consumed by the PIC24FJ64GU205 and its peripherals, approximately 100
µA will be drawn from any external power source to power the on-board level shifters and voltage monitor
circuitry when a USB cable is plugged in the DEBUG connector on the board. When a USB cable is not
plugged in, some current is used to supply the level shifters voltage pins, which have a worst-case current
consumption of approximately 5 µA. Typical values may be as low as 100 nA.
3.3.3 VBUS Output Pin
PIC24FJ64GU205 Curiosity Nano has a VBUS output pin that can be used to power external components that need
a 5V supply. The VBUS output pin has a PTC fuse to protect the USB against short circuits. A side effect of the PTC
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fuse is a voltage drop on the VBUS output with higher current loads. The chart below shows the voltage versus the
current load of the VBUS output.
Figure 3-6. VBUS Output Voltage vs. Current
3.3.4 Power Supply Exceptions
This is a summary of most exceptions that can occur with the power supply.
Target Voltage Shuts Down
This can happen if the target section draws too much current at a given voltage and cause the thermal shutdown
safety feature of the MIC5353 regulator to kick in. To avoid this, reduce the current load of the target section.
Target Voltage Setting is Not Reached
The USB input voltage (specified to be 4.4V-5.25V) limits the maximum output voltage, the voltage drop over the
MIC5353 regulator at a given voltage setting and current consumption. If a higher output voltage is needed, use a
USB power source that can provide a higher input voltage or use an external voltage supply on the VTG pin.
Target Voltage is Different From Setting
This can be caused by an externally applied voltage to the VTG pin without setting the VOFF pin low. If the target
voltage differs more than 100 mV over/under the voltage setting, it will be detected by the on-board debugger, and
the internal voltage regulator will shut down. To fix this issue, remove the applied voltage from the VTG pin, and the
on-board debugger will enable the on-board voltage regulator when the new condition is detected. Note that the PS
LED will be blinking rapidly if the target voltage is below 100 mV of the setting but will normally be lit when it is higher
than 100 mV above the setting.
No, Or Very Low Target Voltage, and PS LED is Blinking Rapidly
This can be caused by a full or partial short-circuit and is a special case of the issue mentioned above. Remove the
short-circuit, and the on-board debugger will re-enable the on-board target voltage regulator.
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No Target Voltage and PS LED is Lit 1
This occurs if the target voltage is set to 0.0V. To fix this, set the target voltage to a value within the specified voltage
range for the target device.
No Target Voltage and PS LED is Lit 2
This can be the issue if power jumper J100 and/or J101 is cut, and the target voltage regulator is set to a value within
the specified voltage range for the target device. To fix this, solder a wire/bridge between the pads for J100/J101, or
add a jumper on J101 if a pin-header is mounted.
VBUS Output Voltage is Low or Not Present
This is most likely caused by a high-current drain on VBUS, and the protection fuse (PTC) will reduce the current or
cut off completely. Reduce the current consumption on the VBUS pin to fix this issue.
3.4 Low-Power Measurement
Power to the PIC24FJ64GU205 is connected from the on-board power supply and VTG pin through a 100 mil
pin-header marked with “POWER” in silkscreen (J101). To measure the power consumption of the PIC24FJ64GU205
and other peripherals connected to the board, cut the Target Power strap and connect an ammeter over the strap.
To measure the lowest possible power consumption, follow these steps:
1. Cut the POWER strap with a sharp tool.
2. Solder a 1x2 100 mil pin-header in the footprint.
3. Connect an ammeter to the pin-header.
4. Write firmware that:
4.1. Tri-states any I/O connected to the on-board debugger.
4.2. Sets the microcontroller in its lowest power sleep mode.
5. Program the firmware into the PIC24FJ64GU205.
Figure 3-7. Target Power Strap
Target Power strap (top side)
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Tip: A 100-mil pin-header can be soldered into the Target Power strap (J101) footprint for easy
connection of an ammeter. Once the ammeter is no longer needed, place a jumper cap on the pin-header.
Info: The on-board level shifters will draw a small amount of current even when they are not in use. A
maximum of 2 µA can be drawn from each I/O pin connected to a level shifter for a total of 10 µA. Keep
any I/O pin connected to a level shifter in tri-state to prevent leakage. All I/Os connected to the on-board
debugger are listed in 4.2.6.1 On-Board Debugger Connections. To prevent any leakage to the on-board
level shifters, they can be disconnected completely, as described in 7.4 Disconnecting the On-Board
Debugger.
3.5 Programming External Microcontrollers
The on-board debugger on PIC24FJ64GU205 Curiosity Nano can be used to program and debug microcontrollers on
external hardware.
3.5.1 Supported Devices
All external AVR microcontrollers with the UPDI interface can be programmed and debugged with the on-board
debugger with Microchip Studio.
External SAM microcontrollers that have a Curiosity Nano Board can be programmed and debugged with the
on-board debugger with Microchip Studio.
PIC24FJ64GU205 Curiosity Nano can program and debug external PIC24FJ64GU205 microcontrollers with MPLAB
X IDE.
3.5.2 Software Configuration
No software configuration is required to program and debug the same device that is mounted on the board.
To program and debug a different microcontroller than what is mounted on the board, Microchip Studio must be
configured to allow free selection of devices and programming interfaces.
1. Navigate to Tools > Options through the menu system at the top of the application.
2. Select the Tools > Tool settings category in the options window.
3. Set the Hide unsupported devices option to False.
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Figure 3-8. Hide Unsupported Devices
Info: Microchip Studio allows any microcontroller and interface to be selected when the Hide
unsupported devices setting is set to False, also microcontrollers and interfaces which are not supported
by the on-board debugger.
3.5.3 Hardware Modifications
The on-board debugger is connected to the PIC24FJ64GU205 by default. Remove these connections before any
external microcontroller can be programmed or debugged. Cut the GPIO straps shown in the figure below with a
sharp tool to disconnect the PIC24FJ64GU205 from the on-board debugger.
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