Laird RM126 Series User manual

A
Version 1.0

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Version
Date
Notes
Contributors
Approver
1.0
23 May 2023
Initial Release
Raj Khatri
Senthooran
Ragavan

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1Overview .............................................................................................................................................................................4
2Laird Connectivity RM126x Part Numbers...........................................................................................................................4
3Kit Contents.........................................................................................................................................................................4
4Main Board –Features........................................................................................................................................................5
4.1 Key Features..............................................................................................................................................................5
5Understanding the Development Board...............................................................................................................................6
6Specifications ......................................................................................................................................................................7
6.1 Recommended Operating Conditions ........................................................................................................................7
6.2 Current Consumption..................................................................................................................................................7
7Functional Blocks ................................................................................................................................................................8
7.1 Hardware Block Diagram ...........................................................................................................................................8
7.2 Power Supply.............................................................................................................................................................8
7.3 RM126x Reset............................................................................................................................................................9
7.4 Push Button and LED.................................................................................................................................................9
7.4.1 BOOT pin (PC06) and BUTTON 0 (silkscreen BTN0)..........................................................................................9
7.5 On-board Debugger ...................................................................................................................................................9
7.6 Hardware Connectors ..............................................................................................................................................11
7.6.1 Breakout Pads Pinout.........................................................................................................................................12
7.6.2 MikroBUS Socket ...............................................................................................................................................14
7.6.3 Qwiic Connector .................................................................................................................................................16
7.6.4 Debug USB Micro-B Connector..........................................................................................................................16
8Debugging.........................................................................................................................................................................17
8.1 On-board Debugger .................................................................................................................................................17
8.2 Virtual COM Port......................................................................................................................................................17
9Schematic, Assembly Drawing, 3DModel..........................................................................................................................17

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The RM126x Development Kit is an ultra-low cost, small form factor development and evaluation platform for the RM126x
Wireless LoRaWAN Module.
The RM126x Development Kit is focused on rapid prototyping and concept creation of IoT applications. It is designed around
the RM126x Module, based on the EFR32BG22 System-on-Chip and SX126x LoRa chipset, which is an ideal device family for
developing energy-friendly connected IoT applications.
The kit features a USB interface, an on-board SEGGER J-Link debugger, one user-LED and button, and support for hardware
add-on boards via a mikroBus socket and a Qwiic connector. The hardware add-on support allows developers to create and
prototype applications using a virtually endless combination of off-the-shelf boards from mikroE, sparkfun, AdaFruit, and
Seeed Studios.
Module
▪RM126x (RM1261 / RM1262) LoRaWAN Module
▪32-bit ARM® Cortex®-M33 with 76.8 MHz maximum operating frequency
▪512 kB flash and 32 kB RAM
Features
▪User LED and push button
▪20-pin 2.54 mm breakout pads
▪mikroBUS™socket
▪Qwiic® connector
▪SEGGER J-Link on-board debugger
▪Virtual COM port
▪Packet Trace Interface (PTI)
▪USB-powered.
Software
▪AT Command Set (Laird Connectivity created) - Fully featured and extensible, proven over 5+ years
▪Native C development Code (Customer created)- Full software development with Silicon Labs SDK
and toolchain. Use Simplicity Studio IDE for full functionality of Silicon Labs HW/SW
Part Number
Description
453-00140-K1
Development Kit, RM1261, SX1261, MHF4
453-00139-K1
Development Kit, RM1262, SX1262, MHF4
Applicable to following RM126x part numbers:
Part Number
Product Description
453-00140
Module, RM1261, SX1261, MHF4
453-00139
Module, RM1262, SX1262, MHF4
All kits contain the following items:
Development Board
Contains soldered RM1261 / RM1262 module and exposes all available hardware interfaces.
Power Options
USB cable (x1) –Type A to micro type B. Also provides serial via onboard USB –UART chip
Antenna with RM1261
1 x Laird FlexPIFA 868MHz antenna
1 x Laird iFlexPIFA 915MHz antenna
Antenna with RM1262
1 x Laird iFlexPIFA 915MHz antenna

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The RM126x Development Kit has been designed to simplify IoT development with the RM126x wireless module. The kit
includes a mikroBUS™socket and Qwiic® connector, allowing users to add features to the kit with a large selection of off-the-
shelf boards.
Programming the RM126x Development Kit is easily done using a USB Micro-B cable and the on-board J-Link debugger. A
USB virtual COM port provides a serial connection to the target application.
The RM126x Development board Kit DVK-RM126x ships with signed RM126x Bootloader and AT application firmware
(customer using AT commands run from a host). Alternatively, the RM126x is supported in Silicon Labs’ Simplicity Studio™
and an initial Board Support Package (BSP) is provided by Silicon labs to give application developers a flying start. Laird
Connectivity provides extensive sample applications RM126x for those customers developing with C code developing with the
Silicon Labs SDK, including the mandatory RM126x radio regulatory protection layer.
Connecting external hardware to the RM126x Development Kit can be done using the 20 breakout pads which present
peripherals from the RM126x such as I2C, SPI, UART and GPIOs. The mikroBUS socket allows inserting mikroBUS add-on
boards which interface with the RM126x through SPI, UART or I2C. The Qwiic connector can be used to connect hardware
from the Qwiic Connect System through I2C.
The following key hardware elements are included on the RM126x Development Kit:
▪RM126x (RM1261 / RM1262) LoRaWAN Module (EFR32 with 76.8 MHz operating frequency), connecting to external
antenna (MHF4), 512 kB flash, and 32 kB RAM
▪One LED and one push button
▪On-board SEGGER J-Link debugger for easy programming and debugging, which includes a USB virtual COM port
and Packet Trace Interface (PTI)
▪MikroBUS™socket for connecting click boards™and other mikroBUS add-on boards
▪Qwiic® connector for connecting Qwiic Connect System hardware
▪Breakout pads for GPIO access and connection to external hardware
▪Reset button
▪DVK-RM126x ships with signed RM126x Bootloader and AT application firmware (customer using AT commands run
from a host)

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Figure 1: RM126x development board layout
Note: Example given is for the RM1262 development board. The development boards are identical with the exception of
the included module (RM1261 or RM1262).

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Table 1: Recommended operating conditions
Parameter
Symbol
Min
Typ
Max
Unit
USB Supply Input Voltage
VUSB
-
+5.0
-
V
Supply Input Voltage (VMCU1 supplied externally)
VVMCU1
+3.31
V
Operating Temperature
TOP
-
+20
-
˚C
1 The typical supply voltage to the RM126x is 3.3 V, but the maximum voltage is a function of temperature and average lifetime
current load. See the RM126x datasheet for more information.
The operating current of the board greatly depends on the application and the amount of external hardware connected. See
Table 2 for typical current consumptions for the RM126x and the on-board debugger. Note that the numbers are taken from
the data sheets for the devices. For a full overview, see the RM126x datasheet.
Table 2: Current consumption
Parameter
Symbol
Condition
Typ
Unit
Radio RX current
(RM1261 or
RM1262)
IRX_LORA
IRX_FSK
RM1261 or RM1261 LoRa radio system current consumption
in Receive mode - RX Boosted, LoRa. Running radio test
firmware, EUART open. (VDD=3.3V, at 25 ˚C).
8.1
mA
RM1261 or RM1261 FSK radio system current consumption
in Receive mode - RX Boosted, FSK 50kbps. Running radio
test firmware, EUART open. (VDD = 3.3V, at 25 ˚C).
7.6
mA
Radio TX current
(RM1261)
ITX_LORA
RM1261 LoRa radio system current consumption in Transmit
mode @ 14dBm, 915MHz (VDD=3.0 V, at 25 ˚C).
28.8
mA
Radio TX current
(RM1262)
ITX_LORA
RM1262 LoRa radio system current consumption in Transmit
mode @ 22dBm, 915MHz (VDD=3.0 Vat 25 ˚C). VDD=3.3V
minimum to achieve RF TX power 22dBm.
109
mA
On-board Debugger
Sleep Current
Consumption2
IDBG
On-board debugger current consumption when USB cableis
not inserted (EFM32GG12 EM4S mode current
consumption).
80
nA
1 From RM126x data sheet
2 From EFR32BG22 data sheet

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The core of the RM126x Development Kit is the RM126x LoRaWAN Module. Refer to Understanding the Development Board
for placement and layout of the hardware components.
An overview of the RM126x Development Kit is illustrated in the figure below.
Figure 2: RM126x DVK block diagram
The kit is powered by the debug USB cable as illustrated in the figure below.
Figure 3: RM126x DVK power diagram

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The 5 volt power net on the USB bus is regulated down to 3.3 V using an LDO (low-dropout regulator). An automatic isolation
circuit isolates the LDO when the USB cable is not plugged in.
Power can be injected externally on the VMCU1 net if the USB cable is removed, and no other power sources are present on
the kit. Failure to follow this guideline can cause power conflicts and damage the LDO.
The RM126x can be reset by a few different sources:
▪A user pressing the RESET button.
▪The on-board debugger pulling the #RESET pin low.
The kit has one user push button marked BTN0 and one LED marked LED0 that are each connected to a GPIO on the
RM126x. The button is connected to pin PC06 and it is debounced by an RC filter with a time constant of 1 ms. The logic
state of the button is high while the button is not being pressed, and low when the button is pressed. The LED is configurable
in firmware for user’s application. See BOOT pin (PC06) and BUTTON 0 (silkscreen BTN0) usage information.
Figure 4: RM126x DVK Button and LED
For the RM126x module the BOOT pin is on PC06 (pin19). On the RM126x development board BTN0 (Button0) is by default
mapped to the BOOT pin for easier utilisation.
The BOOT pin (PC06) is used to determine when execution of the bootloader is required. Upon reset, execution of the
bootloader begins. The state of the BOOT pin is read immediately upon start-up of the bootloader. If LOW (BTN0 pressed),
execution of the bootloader continues, facilitating firmware update via the UART. If the BOOT pin is HIGH (BTN0 not pressed),
the bootloader will stop execution and pass control to the main application firmware.
Please refer to respective DVK schematics and Serial DFU section of User Guide - Firmware Options and Upgrading –
RM126x Series for more information at:
https://www.lairdconnect.com/rm126x-series
The RM126x Development Kit contains a microcontroller separate from the RM126x that provides the user with an on- board
J-Link debugger through the USB Micro-B port. This microcontroller is referred to as the "on-board debugger”and is not
programmable by the user. When the USB cable is removed, the on-board debugger goes into a very low power shutoff mode
(EM4S), consuming around 80 nA typically (EFM32GG12 data sheet number).
In addition to providing code download and debug features, the on-board debugger also presents a virtual COM port for
general purpose application serial data transfer. The Packet Trace Interface (PTI) is also supported which offers
invaluable debug information about transmitted and received packets in wireless links.
The figure below shows the connections between the target RM126x device and the on-board debugger. See Debugging for
more details.

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Figure 5: RM126x DVK Debugger Connections