================= stm32f103-minimum ================= This page discusses issues unique to NuttX configurations for the STM32F103C8T6 Minimum System Development Board for ARM Microcontroller. STM32F103C8T6 Minimum System Development Boards: ================================================ This STM32F103C8T6 minimum system development board is available from several vendors on the net, and may be sold under different names or no name at all. It is based on a STM32F103C8T6 and has a DIP-40 form- factor. There are four versions of very similar boards: Red, Blue, RoboDyn Black and Black. See: https://wiki.stm32duino.com/index.php?title=Blue_Pill https://wiki.stm32duino.com/index.php?title=Red_Pill https://wiki.stm32duino.com/index.php?title=RobotDyn_Black_Pill https://wiki.stm32duino.com/index.php?title=Black_Pill The Red Board: Good things about the red board: - 1.5k pull up resistor on the PA12 pin (USB D+) which you can programmatically drag down for automated USB reset. - large power capacitors and LDO power. - User LED on PC13 Problems with the red board: - Silk screen is barely readable, the text is chopped off on some of the pins - USB connector only has two anchor points and it is directly soldered on the surface - Small reset button with hardly any resistance The Blue Board: Good things about the blue board: - Four soldered anchor point on the USB connector. What you can't tell from this picture is that there is a notch in the PCB board and the USB connector sits down inside it some. This provides some lateral stability that takes some of the stress off the solder points. - It has nice clear readable silkscreen printing. - It also a larger reset button. - User LED on PC13 Problems with the blue board: - Probably won't work as a USB device if it has a 10k pull-up on PA12. You have to check the pull up on PA12 (USB D+). If it has a 10k pull-up resistor, you will need to replace it with a 1.5k one to use the native USB. - Puny voltage regulator probably 100mA. A schematic for the blue board is available here: http://www.stm32duino.com/download/file.php?id=276 The Black Board: - User LED is on PB12. - Mounting holes. Both Boards: Nice features common to both: - SWD pins broken out and easily connected (VCC, GND, SWDIO, SWCLK) - USB 5V is broken out with easy access. - Power LED - You can probably use more flash (128k) than officially documented for the chip (stm32f103c8t6 64k), I was able to load 115k of flash on mine and it seemed to work. Problems with both boards: - No preloaded bootloader (this isn't really a problem as the entire 64k of flash is available for use) - No user button This is the board pinout based on its form-factor for the Blue board: .. USB ___ -----/ _ \----- |B12 GND| |B13 GND| |B14 3.3V| |B15 RST| |A8 B11| |A9 B10| |A10 B1| |A11 B0| |A12 A7| |A15 A6| |B3 A5| |B4 A4| |B5 A3| |B6 A2| |B7 A1| |B8 A0| |B9 C15| |5V C14| |GND C13| |3.3V VB| |_____________| LEDs ==== The STM32F103 Minimum board has only one software controllable LED. This LED can be used by the board port when CONFIG_ARCH_LEDS option is enabled. If enabled the LED is simply turned on when the board boots successfully, and is blinking on panic / assertion failed. UARTs ===== UART/USART PINS --------------- .. USART1 RX PA10 TX PA9 USART2 CK PA4 CTS PA0 RTS PA1 RX PA3 TX PA2 USART3 CK PB12 CTS PB13 RTS PB14 RX PB11 TX PB10 Default USART/UART Configuration -------------------------------- USART1 (RX & TX only) is available through pins PA9 (TX) and PA10 (RX). Timer Inputs/Outputs ==================== .. TIM1 CH1 PA8 CH2 PA9* CH3 PA10* CH4 PA11* TIM2 CH1 PA0*, PA15, PA5 CH2 PA1, PB3 CH3 PA2, PB10* CH4 PA3, PB11 TIM3 CH1 PA6, PB4 CH2 PA7, PB5* CH3 PB0 CH4 PB1* TIM4 CH1 PB6* CH2 PB7 CH3 PB8 CH4 PB9* * Indicates pins that have other on-board functions and should be used only with care (See board datasheet). Using 128KiB of Flash instead of 64KiB ====================================== Some people figured out that the STM32F103C8T6 has 128KiB of internal memory instead of 64KiB as documented in the datasheet and reported by its internal register. In order to enable 128KiB you need modify the linker script to reflect this new size. Open the boards/arm/stm32/stm32f103-minimum/scripts/ld.script and replace:: flash (rx) : ORIGIN = 0x08000000, LENGTH = 64K with:: flash (rx) : ORIGIN = 0x08000000, LENGTH = 128K Enable many NuttX features (ie. many filesystems and applications) to get a large binary image with more than 64K. We will use OpenOCD to write the firmware in the STM32F103C8T6 Flash. Use a up to dated OpenOCD version (ie. openocd-0.9). You will need to create a copy of original openocd/scripts/target/stm32f1x.cfg to openocd/scripts/target/stm32f103c8t6.cfg and edit the later file replacing:: flash bank $_FLASHNAME stm32f1x 0x08000000 0 0 0 $_TARGETNAME with:: flash bank $_FLASHNAME stm32f1x 0x08000000 0x20000 0 0 $_TARGETNAME We will use OpenOCD with STLink-V2 programmer, but it will work with other programmers (JLink, Versaloon, or some based on FTDI FT232, etc). Open a terminal and execute:: $ sudo openocd -f interface/stlink-v2.cfg -f target/stm32f103c8t6.cfg Now in other terminal execute:: $ telnet localhost 4444 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. Open On-Chip Debugger > reset halt stm32f1x.cpu: target state: halted target halted due to debug-request, current mode: Thread xPSR: 0x01000000 pc: 0x080003ac msp: 0x20000d78 > flash write_image erase nuttx.bin 0x08000000 auto erase enabled device id = 0x20036410 ignoring flash probed value, using configured bank size flash size = 128kbytes stm32f1x.cpu: target state: halted target halted due to breakpoint, current mode: Thread xPSR: 0x61000000 pc: 0x2000003a msp: 0x20000d78 wrote 92160 bytes from file nuttx.bin in 4.942194s (18.211 KiB/s) > reset run > exit Now NuttX should start normally. Nintendo Wii Nunchuck: ====================== There is a driver on NuttX to support Nintendo Wii Nunchuck Joystick. If you want to use it please select these options: - Enable the I2C1 at System Type -> STM32 Peripheral Support, it will enable: CONFIG_STM32_I2C1=y - Enable to Custom board/driver initialization at RTOS Features -> RTOS hooks CONFIG_BOARD_LATE_INITIALIZE=y - Enable the I2C Driver Support at Device Drivers, it will enable this symbol: CONFIG_I2C=y - Nintendo Wii Nunchuck Joystick at Device Drivers -> [*] Input Device Support CONFIG_INPUT=y CONFIG_INPUT_NUNCHUCK=y - Enable the Nunchuck joystick example at Application Configuration -> Examples CONFIG_EXAMPLES_NUNCHUCK=y CONFIG_EXAMPLES_NUNCHUCK_DEVNAME="/dev/nunchuck0" You need to connect GND and +3.3V pins from Nunchuck connector to GND and 3.3V of stm32f103-minimum respectively (Nunchuck also can work connected to 5V, but I don't recommend it). Connect I2C Clock from Nunchuck to SCK (PB6) and the I2C Data to SDA (PB7). Quadrature Encoder: =================== The nsh configuration has been used to test the Quadrature Encoder (QEncoder, QE) with the following modifications to the configuration file: - These setting enable support for the common QEncode upper half driver: CONFIG_SENSORS=y CONFIG_SENSORS_QENCODER=y - This is a board setting that selected timer 4 for use with the quadrature encode: CONFIG_STM32F103MINIMUM_QETIMER=4 - These settings enable the STM32 Quadrature encoder on timer 4: CONFIG_STM32_TIM4_CAP=y CONFIG_STM32_TIM4_QE=y CONFIG_STM32_TIM4_QECLKOUT=2800000 CONFIG_STM32_QENCODER_FILTER=y CONFIG_STM32_QENCODER_SAMPLE_EVENT_6=y CONFIG_STM32_QENCODER_SAMPLE_FDTS_4=y - These settings enable the test case at apps/examples/qencoder: CONFIG_EXAMPLES_QENCODER=y CONFIG_EXAMPLES_QENCODER_DELAY=100 CONFIG_EXAMPLES_QENCODER_DEVPATH="/dev/qe0" In this configuration, the QEncoder inputs will be on the TIM4 inputs of PB6 and PB7. SPI NOR Flash support: ====================== We can use an extern SPI NOR Flash with STM32F103-Minimum board. In this case we tested the Winboard W25Q32FV (32Mbit = 4MiB). You can connect the W25Q32FV module in the STM32F103 Minimum board this way: connect PA5 (SPI1 CLK) to CLK; PA7 (SPI1 MOSI) to DI; PA6 (SPI MISO) to DO; PA4 to /CS; Also connect 3.3V to VCC and GND to GND. You can start with default "stm32f103-minimum/nsh" configuration option and enable/disable these options using "make menuconfig" :: System Type ---> STM32 Peripheral Support ---> [*] SPI1 Board Selection ---> [*] MTD driver for external 4Mbyte W25Q32FV FLASH on SPI1 (0) Minor number for the FLASH /dev/smart entry [*] Enable partition support on FLASH (1024,1024,1024,1024) Flash partition size list RTOS Features ---> Stack and heap information ---> (512) Idle thread stack size (1024) Main thread stack size (256) Minimum pthread stack size (1024) Default pthread stack size Device Drivers ---> -*- Memory Technology Device (MTD) Support ---> [*] Support MTD partitions -*- SPI-based W25 FLASH (0) W25 SPI Mode (20000000) W25 SPI Frequency File Systems ---> [ ] Disable pseudo-filesystem operations -*- SMART file system (0xff) FLASH erased state (16) Maximum file name length Memory Management ---> [*] Small memory model Also change the boards/arm/stm32/stm32f103-minimum/scripts/ld.script file to use 128KB of Flash instead 64KB (since this board has a hidden 64KB flash) : MEMORY { flash (rx) : ORIGIN = 0x08000000, LENGTH = 128K sram (rwx) : ORIGIN = 0x20000000, LENGTH = 20K } Then after compiling and flashing the file nuttx.bin you can format and mount the flash this way: nsh> mksmartfs /dev/smart0p0 nsh> mksmartfs /dev/smart0p1 nsh> mksmartfs /dev/smart0p2 nsh> mksmartfs /dev/smart0p3 nsh> mount -t smartfs /dev/smart0p0 /mnt nsh> ls /mnt /mnt: nsh> echo "Testing" > /mnt/file.txt nsh> ls /mnt /mnt: file.txt nsh> cat /mnt/file.txt Testing nsh> SDCard support: =============== Only STM32F103xx High-density devices has SDIO controller. STM32F103C8T6 is a Medium-density device, but we can use SDCard over SPI. You can do that enabling these options:: CONFIG_FS_FAT=y CONFIG_MMCSD=y CONFIG_MMCSD_NSLOTS=1 CONFIG_MMCSD_SPI=y CONFIG_MMCSD_SPICLOCK=20000000 CONFIG_MMCSD_SPIMODE=0 CONFIG_STM32_SPI=y CONFIG_STM32_SPI1=y CONFIG_SPI=y CONFIG_SPI_CALLBACK=y CONFIG_SPI_EXCHANGE=y And connect a SDCard/SPI board on SPI1. Connect the CS pin to PA4, SCK to PA5, MOSI to PA7 and MISO to PA6. Note: some chinese boards use MOSO instead of MISO. Nokia 5110 LCD Display support: =============================== You can connect a low cost Nokia 5110 LCD display in the STM32F103 Minimum board this way: connect PA5 (SPI1 CLK) to CLK; PA7 (SPI1 MOSI) to DIN; PA4 to CE; PA3 to RST; PA2 to DC. Also connect 3.3V to VCC and GND to GND. You can start with default "stm32f103-minimum/nsh" configuration option and enable these options using "make menuconfig" :: System Type ---> STM32 Peripheral Support ---> [*] SPI1 Device Drivers ---> -*- SPI Driver Support ---> [*] SPI exchange [*] SPI CMD/DATA Device Drivers ---> LCD Driver Support ---> [*] Graphic LCD Driver Support ---> [*] Nokia 5110 LCD Display (Phillips PCD8544) (1) Number of PCD8544 Devices (84) PCD8544 X Resolution (48) PCD8544 Y Resolution Graphics Support ---> [*] NX Graphics (1) Number of Color Planes (0x0) Initial background color Supported Pixel Depths ---> [ ] Disable 1 BPP [*] Packed MS First Font Selections ---> (7) Bits in Character Set [*] Mono 5x8 Application Configuration ---> Examples ---> [*] NX graphics "Hello, World!" example (1) Bits-Per-Pixel After compiling and flashing the nuttx.bin inside the board, reset it. You should see it: NuttShell (NSH) nsh> ? help usage: help [-v] [] [ dd free mb source usleep ? echo help mh sleep xd cat exec hexdump mw test cd exit kill pwd true cp false ls set unset Builtin Apps: nxhello Now just run nxhello and you should see "Hello World" in the display: nsh> nxhello HYT271 sensor support ===================== The existing sensor configuration allows connecting several sensors of type hyt271 on i2c bus number 2. For full feature support, be able to change the i2c address of the sensor, the following hardware setup is necessary.:: ---------- ----------- | |------ GND ------------------------ GND ----| | | | | | | | | | | | | | | |---- POWIN A00 ------. | | | | | | | | | 4.7k | | | | | | | | STM32 |--- POWOUT A01 ------.------.------ VDD ----| HYT271 | | | | | | | | | 2.2k | | | | | | | | | | |----- SDA2 B11 ------.---- | ----- SDA ----| | | | | | | | | 2.2k | | | | | | | | |----- SCL2 B10 -------------.------ SCL ----| | | | | | --------- ----------- DS18B20 sensor support ====================== The existing sensor configuration allows connecting several sensors of type ds18b20 on 1wire bus number 2. The following hardware setup is necessary.:: --------- ----------- | |------ GND ----------.------------- GND ----| | | | | | | | | | | | | | | |------ VDD ----------.------------- VDD ----| | | STM32 | | | DS18B20 | | | 4.7k | | | | | | | | |----- TX2 A02 -------.------.------- DQ ----| | | | | | -------- ----------- USB Console support =================== The STM32F103C8 has a USB Device controller, then we can use NuttX support to USB Device. We can the console over USB enabling these options: :: System Type ---> STM32 Peripheral Support ---> [*] USB Device It will enable: CONFIG_STM32_USB=y Board Selection ---> -*- Enable boardctl() interface [*] Enable USB device controls It will enable: CONFIG_BOARDCTL_USBDEVCTRL=y Device Drivers ---> -*- USB Device Driver Support ---> [*] USB Modem (CDC/ACM) support ---> It will enable: CONFIG_CDCACM=y and many default options. Device Drivers ---> -*- USB Device Driver Support ---> [*] USB Modem (CDC/ACM) support ---> [*] CDC/ACM console device It will enable: CONFIG_CDCACM_CONSOLE=y Device Drivers ---> [*] Serial Driver Support ---> Serial console (No serial console) ---> (X) No serial console It will enable: CONFIG_NO_SERIAL_CONSOLE=y After flashing the firmware in the board, unplug and plug it in the computer and it will create a /dev/ttyACM0 device in the Linux. Use minicom with this device to get access to NuttX NSH console (press Enter three times to start) MCP2515 External Module ======================= You can use an external MCP2515 (tested with NiRen MCP2515_CAN module) to get CAN Bus working on STM32F103C8 chip (remember the internal CAN cannot work with USB at same time because they share the SRAM buffer). You can connect the MCP2515 module in the STM32F103 Minimum board this way: connect PA5 (SPI1 CLK) to SCK; PA7 (SPI1 MOSI) to SI; PA6 (SPI MISO) to SO; PA4 to CS; B0 to INT. Also connect 5V to VCC and GND to GND. Note: Although MCP2515 can work with 2.7V-5.5V it is more stable when using it on BluePill board on 5V. Testing: you will need at least 2 boards each one with a MCP2515 module connected to it. Connect CAN High from the first module to the CAN High of the second module, and the CAN Low from the first module to the CAN Low of the second module. You need to modify the "CAN example" application on menuconfig and create two firmware versions: the first firmware will be Read-only and the second one Write-only. Flash the first firmware in the first board and the second firmware in the second board. Now you can start the both boards, run the "can" command in the Write-only board and then run the "can" command in the Read-only board. You should see the data coming. STM32F103 Minimum - specific Configuration Options ================================================== .. CONFIG_ARCH - Identifies the arch/ subdirectory. This should be set to: CONFIG_ARCH=arm CONFIG_ARCH_family - For use in C code: CONFIG_ARCH_ARM=y CONFIG_ARCH_architecture - For use in C code: CONFIG_ARCH_CORTEXM3=y CONFIG_ARCH_CHIP - Identifies the arch/*/chip subdirectory CONFIG_ARCH_CHIP=stm32 CONFIG_ARCH_CHIP_name - For use in C code to identify the exact chip: CONFIG_ARCH_CHIP_STM32F103C8=y CONFIG_ARCH_BOARD_STM32_CUSTOM_CLOCKCONFIG - Enables special STM32 clock configuration features. CONFIG_ARCH_BOARD_STM32_CUSTOM_CLOCKCONFIG=n CONFIG_ARCH_BOARD - Identifies the boards/ subdirectory and hence, the board that supports the particular chip or SoC. CONFIG_ARCH_BOARD=stm32f103-minimum CONFIG_ARCH_BOARD_name - For use in C code CONFIG_ARCH_BOARD_STM32_MINIMUM=y CONFIG_ARCH_LOOPSPERMSEC - Must be calibrated for correct operation of delay loops CONFIG_ENDIAN_BIG - define if big endian (default is little endian) CONFIG_RAM_SIZE - Describes the installed DRAM (SRAM in this case): CONFIG_RAM_SIZE=20480 (20Kb) CONFIG_RAM_START - The start address of installed DRAM CONFIG_RAM_START=0x20000000 CONFIG_ARCH_LEDS - Use LEDs to show state. Unique to boards that have LEDs CONFIG_ARCH_INTERRUPTSTACK - This architecture supports an interrupt stack. If defined, this symbol is the size of the interrupt stack in bytes. If not defined, the user task stacks will be used during interrupt handling. CONFIG_ARCH_STACKDUMP - Do stack dumps after assertions .. Individual subsystems can be enabled: AHB --- CONFIG_STM32_CRC CONFIG_STM32_BKPSRAM APB1 ---- CONFIG_STM32_TIM2 CONFIG_STM32_TIM3 CONFIG_STM32_TIM4 CONFIG_STM32_WWDG CONFIG_STM32_IWDG CONFIG_STM32_SPI2 CONFIG_STM32_USART2 CONFIG_STM32_USART3 CONFIG_STM32_I2C1 CONFIG_STM32_I2C2 CONFIG_STM32_CAN1 CONFIG_STM32_PWR -- Required for RTC APB2 ---- CONFIG_STM32_TIM1 CONFIG_STM32_USART1 CONFIG_STM32_ADC1 CONFIG_STM32_ADC2 CONFIG_STM32_SPI1 Timer devices may be used for different purposes. One special purpose is to generate modulated outputs for such things as motor control. If CONFIG_STM32_TIMn is defined (as above) then the following may also be defined to indicate that the timer is intended to be used for pulsed output modulation or ADC conversion. Note that ADC require two definitions: Not only do you have to assign the timer (n) for used by the ADC, but then you also have to configure which ADC (m) it is assigned to. CONFIG_STM32_TIMn_PWM Reserve timer n for use by PWM, n=1,..,14 CONFIG_STM32_TIMn_ADC Reserve timer n for use by ADC, n=1,..,14 CONFIG_STM32_TIMn_ADCm Reserve timer n to trigger ADCm, n=1,..,14, m=1,..,3 For each timer that is enabled for PWM usage, we need the following additional configuration settings: CONFIG_STM32_TIMx_CHANNEL - Specifies the timer output channel {1,..,4} NOTE: The STM32 timers are each capable of generating different signals on each of the four channels with different duty cycles. That capability is not supported by this driver: Only one output channel per timer. JTAG Enable settings (by default only SW-DP is enabled): CONFIG_STM32_JTAG_FULL_ENABLE - Enables full SWJ (JTAG-DP + SW-DP) CONFIG_STM32_JTAG_NOJNTRST_ENABLE - Enables full SWJ (JTAG-DP + SW-DP) but without JNTRST. CONFIG_STM32_JTAG_SW_ENABLE - Set JTAG-DP disabled and SW-DP enabled STM32F103 Minimum specific device driver settings CONFIG_U[S]ARTn_SERIAL_CONSOLE - selects the USARTn (n=1,2,3) for the console and ttys0 (default is the USART1). CONFIG_U[S]ARTn_RXBUFSIZE - Characters are buffered as received. This specific the size of the receive buffer CONFIG_U[S]ARTn_TXBUFSIZE - Characters are buffered before being sent. This specific the size of the transmit buffer CONFIG_U[S]ARTn_BAUD - The configure BAUD of the UART. Must be CONFIG_U[S]ARTn_BITS - The number of bits. Must be either 7 or 8. CONFIG_U[S]ARTn_PARTIY - 0=no parity, 1=odd parity, 2=even parity CONFIG_U[S]ARTn_2STOP - Two stop bits STM32F103 Minimum CAN Configuration CONFIG_CAN - Enables CAN support (one or both of CONFIG_STM32_CAN1 or CONFIG_STM32_CAN2 must also be defined) CONFIG_CAN_EXTID - Enables support for the 29-bit extended ID. Default Standard 11-bit IDs. CONFIG_CAN_FIFOSIZE - The size of the circular buffer of CAN messages. Default: 8 CONFIG_CAN_NPENDINGRTR - The size of the list of pending RTR requests. Default: 4 CONFIG_CAN_LOOPBACK - A CAN driver may or may not support a loopback mode for testing. The STM32 CAN driver does support loopback mode. CONFIG_STM32_CAN1_BAUD - CAN1 BAUD rate. Required if CONFIG_STM32_CAN1 is defined. CONFIG_STM32_CAN2_BAUD - CAN1 BAUD rate. Required if CONFIG_STM32_CAN2 is defined. CONFIG_STM32_CAN_TSEG1 - The number of CAN time quanta in segment 1. Default: 6 CONFIG_STM32_CAN_TSEG2 - the number of CAN time quanta in segment 2. Default: 7 CONFIG_STM32_CAN_REGDEBUG - If CONFIG_DEBUG_FEATURES is set, this will generate an dump of all CAN registers. STM32F103 Minimum SPI Configuration CONFIG_STM32_SPI_INTERRUPTS - Select to enable interrupt driven SPI support. Non-interrupt-driven, poll-waiting is recommended if the interrupt rate would be to high in the interrupt driven case. CONFIG_STM32_SPIx_DMA - Use DMA to improve SPIx transfer performance. Cannot be used with CONFIG_STM32_SPI_INTERRUPT. Configurations ============== Instantiating Configurations ---------------------------- Each STM32F103 Minimum configuration is maintained in a sub-directory and can be selected as follow:: tools/configure.sh STM32F103 Minimum: Where is one of the following: Configuration Directories ------------------------- nsh --- Configures the NuttShell (nsh) located at apps/examples/nsh. This configuration enables a console on UART1. Support for builtin applications is enabled, but in the base configuration no builtin applications are selected. jlx12864g --------- This is a config example to use the JLX12864G-086 LCD module. To use this LCD you need to connect PA5 (SPI1 CLK) to SCK; PA7 (SPI1 MOSI) to SDA; PA4 to CS; PA3 to RST; PA2 to RS. nrf24 ----- This is a config example to test the nrf24 terminal example. You will need two stm32f103-minimum board each one with a nRF24L01 module connected this way: connect PB1 to nRF24 CE pin; PA4 to CSN; PA5 (SPI1 CLK) to SCK; PA7 (SPI1 MOSI) to MOSI; PA6 (SPI1 MISO) to MISO; PA0 to IRQ. usbnsh ------ This is another NSH example. If differs from other 'nsh' configurations in that this configurations uses a USB serial device for console I/O. NOTES: 1. This configuration uses the mconf-based configuration tool. To change this configuration using that tool, you should: a. Build and install the kconfig-mconf tool. See nuttx/README.txt see additional README.txt files in the NuttX tools repository. b. Execute 'make menuconfig' in nuttx/ in order to start the reconfiguration process. 2. By default, this configuration uses the ARM EABI toolchain for Windows and builds under Cygwin (or probably MSYS). That can easily be reconfigured, of course. CONFIG_HOST_WINDOWS=y : Builds under Windows CONFIG_WINDOWS_CYGWIN=y : Using Cygwin CONFIG_ARM_TOOLCHAIN_GNU_EABI=y : GNU EABI toolchain for Windows 3. This configuration does have UART2 output enabled and set up as the system logging device: CONFIG_SYSLOG_CHAR=y : Use a character device for system logging CONFIG_SYSLOG_DEVPATH="/dev/ttyS0" : UART2 will be /dev/ttyS0 However, there is nothing to generate SYSLOG output in the default configuration so nothing should appear on UART2 unless you enable some debug output or enable the USB monitor. 4. Enabling USB monitor SYSLOG output. If tracing is enabled, the USB device will save encoded trace output in in-memory buffer; if the USB monitor is enabled, that trace buffer will be periodically emptied and dumped to the system logging device (UART2 in this configuration):: CONFIG_USBDEV_TRACE=y : Enable USB trace feature CONFIG_USBDEV_TRACE_NRECORDS=128 : Buffer 128 records in memory CONFIG_NSH_USBDEV_TRACE=n : No builtin tracing from NSH CONFIG_NSH_ARCHINIT=y : Automatically start the USB monitor CONFIG_USBMONITOR=y : Enable the USB monitor daemon CONFIG_USBMONITOR_STACKSIZE=2048 : USB monitor daemon stack size CONFIG_USBMONITOR_PRIORITY=50 : USB monitor daemon priority CONFIG_USBMONITOR_INTERVAL=2 : Dump trace data every 2 seconds CONFIG_USBMONITOR_TRACEINIT=y : Enable TRACE output CONFIG_USBMONITOR_TRACECLASS=y CONFIG_USBMONITOR_TRACETRANSFERS=y CONFIG_USBMONITOR_TRACECONTROLLER=y CONFIG_USBMONITOR_TRACEINTERRUPTS=y 5. By default, this project assumes that you are *NOT* using the DFU bootloader. Using the Prolifics PL2303 Emulation ------------------------------------ You could also use the non-standard PL2303 serial device instead of the standard CDC/ACM serial device by changing:: CONFIG_CDCACM=y : Disable the CDC/ACM serial device class CONFIG_CDCACM_CONSOLE=y : The CDC/ACM serial device is NOT the console CONFIG_PL2303=y : The Prolifics PL2303 emulation is enabled CONFIG_PL2303_CONSOLE=y : The PL2303 serial device is the console veml6070 -------- This is a config example to use the Vishay VEML6070 UV-A sensor. To use this sensor you need to connect PB6 (I2C1 CLK) to SCL; PB7 (I2C1 SDA) to SDA of sensor module. I used a GY-VEML6070 module to test this driver.