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. October 2010 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) Doc ID 15952 Rev 4 1/24 www.st.com Contents UM0742 Contents 1 Description of the STM8T141-EVAL kit . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.1 1.2 2 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 STM8T141 plug-in modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 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 2/24 Doc ID 15952 Rev 4 UM0742 List of tables List of tables Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Table 9. Table 10. STM8T141 main features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 STM8T141 configuration color coding and marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Option bytes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 STM8T141 module pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Copper plane configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 STM8T141 board in standalone mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 STM8T141 board powered through USB supply with earth connection . . . . . . . . . . . . . . . 15 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Doc ID 15952 Rev 4 3/24 List of figures UM0742 List of figures Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14. 4/24 STM8T141-EVAL evaluation kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 MB858 evaluation board with STM8T141 module plugged-in . . . . . . . . . . . . . . . . . . . . . . . 6 MB858 evaluation board top layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 MB858 evaluation board bottom layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 MB858 evaluation board top copper plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 MB858 evaluation board bottom copper plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 STM8T141 module assembly drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 On-board sensing electrode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 On-board sensing electrode configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 On-board sensing electrode with external antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 STM8T141 programming tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 STM8T141 blank module box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 STM8T141 evaluation board (MB858) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 STM8T141 module (MB856) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Doc ID 15952 Rev 4 UM0742 1 Description of the STM8T141-EVAL kit 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 Doc ID 15952 Rev 4 5/24 Description of the STM8T141-EVAL kit 1.1 UM0742 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 MB858 evaluation board STM8T141 module Pin 1 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 GND Grab pin Power supply switch Current measurement connector DIP14 module footprint Sensing electrode Antenna connector Sensing electrode hatched copper plane shield/grounding selection 6/24 Doc ID 15952 Rev 4 UM0742 Description of the STM8T141-EVAL kit Figure 4. MB858 evaluation board bottom layout Battery socket USB power connector 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. Doc ID 15952 Rev 4 7/24 Description of the STM8T141-EVAL kit 1.1.5 UM0742 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 Top copper plane (CP1) Figure 6. MB858 evaluation board bottom copper plane Bottom copper plane (CP2) Hatched copper plane (HCP) 8/24 Doc ID 15952 Rev 4 UM0742 1.2 Description of the STM8T141-EVAL kit 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 Table 2 and Figure 7). Refer to Table 4 for the description of STM8T141 module pins. Table 2. STM8T141 configuration color coding and marking PCB color Module configuration PCB marking LED color Proximity detection No marking Blue Sensitive Touch detection White dot ink marking Red Green 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 Doc ID 15952 Rev 4 125 kHz 9/24 Description of the STM8T141-EVAL kit Table 4. UM0742 STM8T141 module pin description Pin number Pin name 1 SHOUT 2 ELEC 3 NC 4 TOUT/POUT 5 NC Not connected 6 CS 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 14 NC Figure 7. Description Shield output Electrode Not connected Touch/Proximity output Internal voltage regulator output Not connected STM8T141 module assembly drawing Pin 1 Touch/Proximity output LED 10/24 Doc ID 15952 Rev 4 UM0742 2 Getting started with the MB858 evaluation board 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 Doc ID 15952 Rev 4 11/24 Getting started with the MB858 evaluation board Figure 9. UM0742 On-board sensing electrode configuration 4x ai15076 12/24 Doc ID 15952 Rev 4 UM0742 2.2 Getting started with the MB858 evaluation board 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. Doc ID 15952 Rev 4 13/24 Getting started with the MB858 evaluation board 2.3 UM0742 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. Table 5 shows how to configure the board jumpers for each copper plane. Table 5. Copper plane configuration Copper plane Description Shield connection CP1 Ground connection Shield connection CP2 Ground connection Shield connection HCP Ground connection 14/24 Doc ID 15952 Rev 4 UM0742 3 Performance 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. Table 6 and Table 7 show the MB858 evaluation board performance in typical operating conditions. Table 6. STM8T141 board in standalone mode Device Configuration Description Performance – – – – Sensitive touch Low power mode with zoom Battery supply JP3 connected to shield (SHLD) Touch configuration using onboard 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 STM8T141 Table 7. STM8T141 board powered through USB supply with earth connection Device STM8T141 Configuration – – – – Description Proximity Low power mode with zoom USB supply JP3 connected to shield (SHLD) – Proximity – Low power mode with zoom – USB supply Performance Proximity/touch configuration using on-board electrode Proximity detection in the range of 5 cm Proximity/touch configuration using external antenna Proximity detection in the range of 12 cm Doc ID 15952 Rev 4 15/24 Troubleshooting 4 UM0742 Troubleshooting Table 8 provides the answers to the most common questions related to unexpected behavior or unspecified operating conditions. Table 8. Troubleshooting Problem Probable cause Remedy No system protection preventing the Use a casing to protect the PCB user from touching the PCB. The LED is switched on when holding or touching the board Poor system grounding In proximity detection, the LED is switched on when moving the Wrong shielding configuration hand close to some PCB areas The LED is switched on when moving the board The LED is permanently switched on after a detection occurs in proximity configuration 16/24 Connect board ground to earth by connecting the USB cable to a HUB supplied with an earth outlet. 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 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. 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. Doc ID 15952 Rev 4 UM0742 5 Programming tools 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 Doc ID 15952 Rev 4 17/24 Ordering information 6 UM0742 Ordering information Table 9 gives the list of the order codes. Table 9. Order codes(1) Part number Order codes STM8T141-EVAL STM8T141-EVAL STM8T-MOD Description STM8T141 evaluation kit (described in this user manual) Box containing 10 MB856 blank modules based on STM8T141AM-MOD STM8T141AM61T (OTP device in SO8 package) (see Figure 12)(2) ST-TSLINK ST-TSLINK STM8T14X-SB STM8T14X-SB Programming dongle for STM8T141 devices and STM8T14X-SB socket boards. Socket board for STM8T141 devices. 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. 2. In addition to the STM8T141-EVAL evaluation kit, additional STM8T141 “blank” modules (STM8T141AMMOD) can be ordered separately, with the device option bytes left unprogrammed. Figure 12. STM8T141 blank module box 18/24 Doc ID 15952 Rev 4 UM0742 7 Schematics Schematics This section shows the design schematics for the STM8T141-EVAL kit: ● MB858 evaluation board (see Figure 13) ● STM8T141 module (see Figure 14) Doc ID 15952 Rev 4 19/24 D C B SHLD-OUT R1 0R_0603 1 copper plane 1 3 1 2 3 4 0 USBMINI-B-SMT VCC DD+ GND SHIELD CN1 2 GND 1 GND 2 1 R2 DNF 0R_0603 copper plane 2 3 TestPin GND TP1 2xCR2016 (3V165mA) CN2 SHLD-OUT GND BAV70 3 BT1 Battery 20mm 1 2 D1 JP2 IDD 2 A 3 2 1 GND 1 GND VDD 2 3 2 GND CS PROX-OUT SHLD-OUT ELECTRODE ON/OFF 1 S1 JP3 1 2 3 4 5 6 7 GND 1 2 hatched SHLD-OUT JUMPER 3 POS STM8T141 SHLD-OUT VDD ELECTRODE VREG NC NC PROX-OUT SHLD-OUT NC NC CS CX VSS NC U1 2 Doc ID 15952 Rev 4 3 20/24 14 13 12 11 10 9 8 CX JP1 MB858 Revision: STMicroelectronics 190, avenue Célestin COQ 13106 ROUSSET Cedex FRANCE QTOUCH ELECTRODE K1 C-00 1 4 D C B A 3 4 £ Date: 28/Jul/09 Sheet 1 of 1 File: R:\Mcd\GUILHOT\Altium\MB858c - STM8T14x Evaluation Board\MB858c - STM8T14x Evaluation Board Altium databa Number: A4 Size: 2 STM8T14x Evaluation Board ELECTRODE JUMPER 3 POS 3 Title SHLD-OUT VDD VREG 3 1 1 Schematics UM0742 Figure 13. STM8T141 evaluation board (MB858) R3 R2 Doc ID 15952 Rev 4 4 VREG SH OUT VDD T/POUT STM8T141 SH IN CX CS VSS U1 C4 47nF_COG_1206 GND GND 0R_0603 2K_1%_0603 3 2 1 5 6 7 8 1µF_X5R_0603 C3 VCC C2 1µF_X5R_0603 LED CMS 0603 LD1 2K_1%_0603 R4 100K_1%_0603 R1 100nF_X7R_0603 GND C1 7 6 4 2 1 GND 14 CX 9 VREG 13 STM8T14X Module VSS CS TOUT ELEC SH OUT VDD VCC UM0742 Schematics Figure 14. STM8T141 module (MB856) 21/24 Reference documents 8 22/24 UM0742 Reference documents ● STM8T141 datasheet ● STM8T14X-SB data brief Doc ID 15952 Rev 4 UM0742 9 Revision history Revision history Table 10. Document revision history Date Revision Changes 10-Sep-2009 1 Initial release 20-Nov-2009 2 Minor modification to Section 1.2. 08-Feb-2010 3 Table 8: updated with an additional problem, cause and remedy. 15-Oct-2010 4 Changed STM8T14X-EVAL to STM8T141-EVAL. Modified VDD voltage range in Table 1. 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