ST STM8T141-EVAL User manual

October 2010 Doc ID 15952 Rev 4 1/24
UM0742
User manual
STM8T141-EVAL evaluation kit
Introduction
The STM8T141-EVAL is an evaluation kit which introduces developers to
STMicroelectronics STM8T141 touch and proximity capacitive sensor.
It contains an STM8T141 evaluation board, the MB858, plus a set of preconfigured plug-in
modules which can evaluate STM8T141 device performances in either touch or proximity
detection (depending on the module which has been plugged in).
The evaluation kit features are the following:
■Touch detection with on-board PCB sensing electrode and 1.5 mm dielectric panel
■Easy dielectric adjustment by stacking acrylic panels
■Proximity detection with on-board PCB sensing electrode or plug-in antenna
■Standalone power configuration using an on-board battery
■External power supply through USB interface
■Electrode grounding or shielding configured by jumper
Table 1. STM8T141 main features
Features STM8T141
Sensing channel 1
Proximity detection range A few cm
Outputs 1 (Touch or Proximity)
Sampling capacitor External
Active shield Yes
VDD 2.0 to 5.5 V
IDD in Normal power mode (typ) 30 µA
IDD in Low power mode 11 µA
Packages SO8 narrow or UFDFPN8 (2 x 3 mm)
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Contents UM0742
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Contents
1 Description of the STM8T141-EVAL kit . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1 MB858 evaluation board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1.1 Module socket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.1.2 Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.1.3 On-board sensing electrode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.1.4 Antenna connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.1.5 Copper planes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.2 STM8T141 plug-in modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2 Getting started with the MB858 evaluation board . . . . . . . . . . . . . . . . 11
2.1 Using the on-board sensing electrode . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2 Installing an external shielded antenna . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3 Shielding and grounding configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5 Programming tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6 Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7 Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
8 Reference documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
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UM0742 List of tables
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List of tables
Table 1. STM8T141 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Table 2. STM8T141 configuration color coding and marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Table 3. Option bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Table 4. STM8T141 module pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Table 5. Copper plane configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Table 6. STM8T141 board in standalone mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 7. STM8T141 board powered through USB supply with earth connection . . . . . . . . . . . . . . . 15
Table 8. Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 9. Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Table 10. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
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List of figures UM0742
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List of figures
Figure 1. STM8T141-EVAL evaluation kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Figure 2. MB858 evaluation board with STM8T141 module plugged-in . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 3. MB858 evaluation board top layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 4. MB858 evaluation board bottom layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 5. MB858 evaluation board top copper plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 6. MB858 evaluation board bottom copper plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Figure 7. STM8T141 module assembly drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 8. On-board sensing electrode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 9. On-board sensing electrode configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 10. On-board sensing electrode with external antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 11. STM8T141 programming tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Figure 12. STM8T141 blank module box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Figure 13. STM8T141 evaluation board (MB858) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Figure 14. STM8T141 module (MB856) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
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UM0742 Description of the STM8T141-EVAL kit
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1 Description of the STM8T141-EVAL kit
The STM8T141-EVAL kit (see Figure 1) includes:
●1 STM8T141 evaluation board (MB858)
●4 STM8T141 preconfigured plug-in modules (MB856)
●1 antenna shielding cable
●1 additional 3 mm acrylic panel
Figure 1. STM8T141-EVAL evaluation kit
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Description of the STM8T141-EVAL kit UM0742
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1.1 MB858 evaluation board
Figure 2 shows the MB858 evaluation board, while Figure 3 and Figure 4 show the board
top and bottom layout.
Figure 2. MB858 evaluation board with STM8T141 module plugged-in
1. This photo is not contractual.
2. Pin 1 identifies the first pin of the module (refer to Table 4).
Figure 3. MB858 evaluation board top layout
Pin 1
STM8T141 module
MB858 evaluation board
Sensing electrode
DIP14 module
footprint
Antenna connector
Sensing electrode hatched copper
plane shield/grounding selection
Power supply switch
Current measurement
connector
GND Grab pin
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UM0742 Description of the STM8T141-EVAL kit
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Figure 4. MB858 evaluation board bottom layout
1.1.1 Module socket
The MB858 evaluation board features an SDIP14 socket to connect the STM8T141 module
(see Figure 3).
1.1.2 Power supply
The evaluation board can be powered by two different sources:
●A 6 V DC battery supply unit composed of two 3 V CR2016 batteries.
●A 5 V DC power supply delivered by the J1 USB connector (cable not provided) (see
Figure 4).
A dual-anode protection diode (D1) prevents power supply current injection.
IDD current can be monitored by connecting an ammeter to JP2 connector (see Figure 3).
Caution: Switch S1 power switch off to preserve batteries when the evaluation board is stored with a
module plugged into it.
1.1.3 On-board sensing electrode
A copper sensing plate deposited on the PCB is used as a sensing electrode for touch and
proximity detection (refer to Figure 3).
1.1.4 Antenna connector
JP1 connector allows to connect an external antenna instead of the on-board sensing
electrode.
USB power
connector
Battery socket
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Description of the STM8T141-EVAL kit UM0742
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1.1.5 Copper planes
Two copper planes (CP1, CP2) and one hatched copper plane (HCP) were laid out onto the
PCB (see Figure 5).
Figure 5. MB858 evaluation board top copper plane
Figure 6. MB858 evaluation board bottom copper plane
Top copper
plane (CP1)
Bottom
Hatched
copper plane (CP2)
copper plane
(HCP)
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UM0742 Description of the STM8T141-EVAL kit
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1.2 STM8T141 plug-in modules
The STM8T141-EVAL includes a set of plug-in modules (see Section 1.1). They allow a
quick and simple evaluation of the STM8T141 main features and performances for different
option byte configurations:
●3 modules configured in proximity mode / no marking
●1 module configured in sensitive touch mode / white marking
The modules incorporate one LED. To allow quick identification of the module configuration
(touch or proximity) when the demonstration is running, the following color codes are used:
●Blue LED corresponds to the proximity configuration
●Red LED corresponds to the touch configuration
Refer to Section 5 for information on programming tools.
The STM8T141 plug-in module PCB is green.
The STM8T141 touch/proximity output (TOUT/POUT) is connected to an LED which is
turned on when a touch or proximity detection occurs. The LED color depends on the
STM8T141 module configuration (refer to Ta bl e 2 and Figure 7). Refer to Ta ble 4 for the
description of STM8T141 module pins.
Table 2. STM8T141 configuration color coding and marking
PCB color Module configuration PCB marking LED color
Green Proximity detection No marking Blue
Sensitive Touch detection White dot ink marking Red
Table 3. Option bytes
Mode Sensitive touch description Standard proximity description
Power mode Low power mode with zoom Low power mode with zoom
Sensitivity threshold Sensitive touch Standard proximity
Recalibration timeout 15 seconds 15 seconds
TOUT/POUT output mode Active Active
Sampling conversion
period 20 ms 20 ms
Charge transfer frequency 125 kHz 125 kHz
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Description of the STM8T141-EVAL kit UM0742
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Figure 7. STM8T141 module assembly drawing
Table 4. STM8T141 module pin description
Pin number Pin name Description
1 SHOUT Shield output
2ELECElectrode
3 NC Not connected
4 TOUT/POUT Touch/Proximity output
5 NC Not connected
6CS
Capacitive sensing channel pin to external sampling
capacitance CS
7 VSS Ground
8 NC Not connected
9 CX Capacitive sensing channel pin to RX (CX serial resistor)
10 NC Not connected
11 NC Not connected
12 NC Not connected
13 VREG Internal voltage regulator output
14 NC Not connected
Touch/Proximity
output LED
Pin 1
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UM0742 Getting started with the MB858 evaluation board
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2 Getting started with the MB858 evaluation board
To run the board:
1. Place the board on a plane surface.
2. Plug a module in the board according to the device and configuration you intend to
evaluate. Make sure that the module is correctly plugged into the socket.
3. Switch on the board.
4. Move your finger or hand close to the touch/proximity electrode:
– The blue LED switches on to indicate a proximity detection.
– The red LED switches on to indicate a touch detection.
Note: To improve sensitivity, connect the MB858 board to your PC through a USB cable. The
board is then ground and powered through the USB interface.
2.1 Using the on-board sensing electrode
A 1.5 mm acrylic panel mounted on the MB858 is used as sensing electrode. To
demonstrate the detection through various dielectric thicknesses, an additional 3 mm panel,
included in the STM8T141-EVAL kit, can be stacked on as shown on Figure 8.
To use the on-board sensing electrode, a jumper must be installed on the JP1 connector as
shown on Figure 9.
Figure 8. On-board sensing electrode
Touch configuration Proximity configuration
3 mm panel
1.5 mm panel
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Getting started with the MB858 evaluation board UM0742
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Figure 9. On-board sensing electrode configuration
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4x
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UM0742 Getting started with the MB858 evaluation board
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2.2 Installing an external shielded antenna
The on-board sensing electrode can be replaced by an external antenna. The user can use
either the antenna provided with the kit, or any other sensing electrode.
To install an external antenna, remove the jumper on JP1, and plug in the antenna.
Figure 10. On-board sensing electrode with external antenna
Caution: Grabbing the external shield antenna might result in incorrect system behavior.
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Getting started with the MB858 evaluation board UM0742
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2.3 Shielding and grounding configuration
The MB858 evaluation board features 3 different independent copper planes (refer to
Section 1.1.5). According to the environment and the application, the overall system
performance and stability can be improved by connecting copper planes to ground or to the
board shield (see Figure 5.).
CP1 and CP2 copper planes can be configured through R1 and R2 resistors, while HCP is
configured through JP3 jumper. The board is delivered with R1 and R2 connected to
ground, and JP3 to the shield.
Tabl e 5 shows how to configure the board jumpers for each copper plane.
Table 5. Copper plane configuration
Copper plane Description
CP1
Shield connection
Ground connection
CP2
Shield connection
Ground connection
HCP
Shield connection
Ground connection
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UM0742 Performance
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3 Performance
The touch and proximity sensing technology is highly dependent on the environment. The
application behavior consequently varies when it is moved from a wooden to a metallic
table. In addition, if the application is moved quickly from one place to another, the board
may detect the environment change and consider it as a touch or proximity detection.
To avoid such behavior, turn off the board when you move it. This will force a recalibration.
Tabl e 6 and Ta b l e 7 show the MB858 evaluation board performance in typical operating
conditions.
Table 6. STM8T141 board in standalone mode
Device Configuration Description Performance
STM8T141
– Sensitive touch
– Low power mode with zoom
– Battery supply
– JP3 connected to shield (SHLD)
Touch configuration using on-
board electrode
Touch detection over 7.5 mm
acrylic panel
– Proximity
– Low power mode with zoom
– Battery supply
– JP3 connected to shield (SHLD)
Proximity configuration using
on-board electrode
Proximity detection in the
range of 3 cm
Table 7. STM8T141 board powered through USB supply with earth connection
Device Configuration Description Performance
STM8T141
– Proximity
– Low power mode with zoom
–USBsupply
– JP3 connected to shield (SHLD)
Proximity/touch configuration
using on-board electrode
Proximity detection in the
range of 5 cm
– Proximity
– Low power mode with zoom
–USBsupply
Proximity/touch configuration
using external antenna
Proximity detection in the
range of 12 cm
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Troubleshooting UM0742
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4 Troubleshooting
Tabl e 8 provides the answers to the most common questions related to unexpected behavior
or unspecified operating conditions.
Table 8. Troubleshooting
Problem Probable cause Remedy
The LED is switched on when
holding or touching the board
No system protection preventing the
user from touching the PCB. Use a casing to protect the PCB
Poor system grounding
Connect board ground to earth by
connecting the USB cable to a HUB
supplied with an earth outlet.
In proximity detection, the LED
is switched on when moving the
hand close to some PCB areas
Wrong shielding configuration
Use the shield output to protect the
corresponding area from detection. A
typical case is electrode back side
detection: to cancel the detection,
configure the electrode back side copper
plane to shield by connecting JP3 to
SHLD.
The LED is switched on when
moving the board
The surrounding environment
changes very quickly when moving
the board. As a consequence, the
earth reference changes. This can
be interpreted as a detection.
Connect the ground of the board to earth
by connecting the USB cable to a HUB
supplied with an earth outlet.
The LED is permanently
switched on after a detection
occurs in proximity
configuration
If the battery charge or quality is not
adequate, the application supply
may decrease upon a detection due
to the current sunk into the LED
when it is switched on. This
changes the detection threshold
and may lock the device on.
– Replace the battery with a new, fully
charged one.
– Use a higher grade battery with better
current stability.
– Use the USB power supply with the
battery removed.
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UM0742 Programming tools
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5 Programming tools
The capacitive sensing devices can be configured through option bytes. Refer to the
STM8T141 datasheet for a detailed description of the option bytes.
The STM8T141 modules can be programmed using the ST-TSLINK programming dongle
and STVP (Visual Programmer) and the STM8T14X-SB socket board (see Figure 11 and
refer to the STM8T14X-SB data brief). For more information on the STM8T141-EVAL
programming tools, visit STMicroelectronics microcontroller support site at
http://www.st.com/mcu.
Figure 11. STM8T141 programming tool
ST-TSLINK
STM8T14X-SB socket board
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Ordering information UM0742
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6 Ordering information
Tabl e 9 gives the list of the order codes.
Figure 12. STM8T141 blank module box
Table 9. Order codes(1)
1. The ST-TSLINK dongle and the STM8T14X-SB socket board are not part of the STM8T141-EVAL
evaluation kit, and must consequently be ordered separately.
Part number Order codes Description
STM8T141-EVAL STM8T141-EVAL STM8T141 evaluation kit (described in this user manual)
STM8T-MOD STM8T141AM-MOD
Box containing 10 MB856 blank modules based on
STM8T141AM61T (OTP device in SO8 package)
(see Figure 12)(2)
2. In addition to the STM8T141-EVAL evaluation kit, additional STM8T141 “blank” modules (STM8T141AM-
MOD) can be ordered separately, with the device option bytes left unprogrammed.
ST-TSLINK ST-TSLINK Programming dongle for STM8T141 devices and
STM8T14X-SB socket boards.
STM8T14X-SB STM8T14X-SB Socket board for STM8T141 devices.
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UM0742 Schematics
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7 Schematics
This section shows the design schematics for the STM8T141-EVAL kit:
●MB858 evaluation board (see Figure 13)
●STM8T141 module (see Figure 14)
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Schematics UM0742
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Figure 13. STM8T141 evaluation board (MB858)
1 1
2 2
3 3
4 4
D D
C C B B
A A
1
STMicroelectronics 190, avenue Célestin COQ 13106 ROUSSET Cedex FRANCE
1
STM8T14x Evaluation Board
MB858 C-00
28/Jul/09 R:\Mcd\GUILHOT\Altium\MB858c - STM8T14x Evaluation Board\MB858c - STM8T14x Evaluation Board Altium datab
a
Title Size: Number: Date: File:
Revision: Sheet of
A4
£
13 2D1
BAV70
SHLD-OUT
1
ELECTRODE
2
NC
3
PROX-OUT
4
NC
5
CS
6
VSS
7NC 8
CX 9 NC 10
SHLD-OUT 11
NC 12
VREG 13
VDD 14
U1 STM8T141
GND
1K1
QTOUCH ELECTRODE
VDD VREG
GND
SHLD-OUT
SHLD-OUT ELECTRODE
CXCS
PROX-OUT
ELECTRODE
VDD GNDGND
VCC 1
D- 2
D+ 3
GND 4
SHIELD 0
CN1 USBMINI-B-SMT
copper plane 1 copper plane 2
GND
hatched
SHLD-OUT
GND
SHLD-OUT
GND
SHLD-OUT
1
2
3
JP1
JUMPER 3 POS
2
3 1S1
ON/OFF
BT1 Battery 20mm
2xCR2016 (3V165mA)
13
2
R10R_0603 13
2
R20R_0603
TP1 TestPin GND
1
2
JP2 IDD
1 2 3
CN2 DNF
1
2
3
JP3
JUMPER 3 POS
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