stm32f401rc-rs485
This page discusses issues unique to NuttX configurations for the NuttX STM32F4-RS485 development board.
Board information
This board was release on NuttX International Workshop 2023 and developed based on STM32F401RCT6 microcontroller.
- STM32F401RCT6 microcontroller features:
Arm 32-bit Cortex®-M4 CPU with FPU
256 Kbytes of Flash memory
64 Kbytes of SRAM
Serial wire debug (SWD) & JTAG interfaces
Up to 81 I/O ports with interrupt capability
Up to 11 communication interfaces
Up to 3 I2C interfaces
Up to 3 USARTs
Up to 4 SPIs
SDIO interface
USB 2.0 full-speed device/host/OTG controller with on-chip PHY
The board features:
Digital I2C Temperature Sensor (TMP75)
2K bits (256x8) I2C EEPROM
On-board RS485 Transceiver
Two Analog Input Stages with Amplifier Buffer
Two Analog Output Stages with Amplifier Buffer
MicroSD Connector supporting 1 or 4-bit bus
Four User LEDs
Four User Buttons
USB for DFU (Device Firmware Update) and USB device functionality, as well as powering the board
Onboard voltage regulator from 5V to 3.3V
SWD Pins for use as STLink (Pin header) and TC2030-IDC 6-Pin Tag-Connect Plug-of-Nails™ Connector
Crystal for HS 8MHz
Crystal for RTC 32.768KHz
Board documentation: https://github.com/lucaszampar/NuttX_STM32F4_RS485_DevBoard
As F4 series have a USB DFuSe-capable BootROM [AN2606], the board can be flashed via dfu-util over USB, or via stm32flash over UART without any debuggers.
LEDs
The STM32F4-RS485 has 4 software controllable LEDs.
LED |
PINS |
|---|---|
LED_1 |
PC0 |
LED_2 |
PC1 |
LED_4 |
PC2 |
LED_5 |
PC3 |
UARTs
The STM32F4-RS485 has 1 USART available for user.
USART6
UART/USART |
PINS |
|---|---|
TX |
PC6 [1] |
RX |
PC7 |
CK |
PA8 |
[1] Warning you make need to reverse RX/TX on some RS-232 converters
SDCard support
The STM32F4-RS485 has 1 SDCard slot connected as below:
SDIO |
PINS |
|---|---|
SDIO_D0 |
PC8 |
SDIO_D1 |
PC9 |
SDIO_D2 |
PC10 |
SDIO_D3 |
PC11 |
SDIO_DK |
PC12 |
EEPROM
The STM32F4-RS485 development board has serial EEPROM HX24LC02B, with 2k bits (256x8) and internally organized with 32 pages of 8 bytes each. It is connected through I2C as below:
I2C |
PINS |
|---|---|
SDA |
PB7 |
SCL |
PB8 |
Users can enable EERPOM support on STM32F4-RS485 by following below configuration:
Configure basic nsh:
./tools/configure.sh -l stm32f401rc-rs485:nsh
Enable the following configs:
CONFIG_DEV_ZERO=y CONFIG_EEPROM=y CONFIG_FS_PROCFS=y CONFIG_I2C=y CONFIG_I2C_EE_24XX=y CONFIG_STM32_I2C1=y
Build and flash the STM32F4-RS485.
Use dd command to write and read data from EEPROM as below:
nsh> dd if=/dev/zero of=/dev/eeprom nsh: dd: write failed: 1 nsh> dd if=/dev/console of=/dev/eeprom bs=1 count=4 (type "Hello") nsh> dd if=/dev/eeprom of=/dev/console bs=4 count=1 Hellonsh>
Temperature Sensor
The STM32F4-RS485 development board has a temperature sensor TMP75 (compatible with LM75) connected through I2C as below:
I2C |
PINS |
|---|---|
SDA |
PB7 |
SCL |
PB8 |
RS485 Transceiver
The STM32F4-RS485 development board has a half-duplex RS-485 transceiver, the BL3085B it is connected through USART2 as below:
USART2 |
PINS |
|---|---|
USART2_RX |
RO |
USART2_RTS |
DE, /RE |
USART2_RX |
DI |
A/D Converter
The STM32F4-RS485 development board has two Analog to Digital converters with Amplifier Buffer (1COS724SR) and connected as below:
PWM |
PINS |
|---|---|
PWM_1 |
PB6 |
PWM_2 |
PA6 |
D/C Converter
The STM32F4-RS485 development board has two Digital to Analog converters with Amplifier Buffer (1COS724SR) and connected as below:
ADC |
PINS |
|---|---|
ADC_1 |
PA0 |
ADC_2 |
PA4 |
Configurations
Each stm32f401rc-rs485 configuration is maintained in a sub-directory and can be selected as follow:
tools/configure.sh stm32f401rc-rs485:<subdir>
Where <subdir> is one of the following:
Configuration Directories
nsh
Configures the NuttShell (nsh) located at apps/examples/nsh. This configuration enables a serial console on USART6.
usbnsh
Configures the NuttShell (nsh) located at apps/examples/nsh. This configuration enables a serial console over USB.
After flasing and reboot your board you should see in your dmesg logs:
[ 2638.948089] usb 1-1.4: new full-speed USB device number 16 using xhci_hcd
[ 2639.054432] usb 1-1.4: New USB device found, idVendor=0525, idProduct=a4a7, bcdDevice= 1.01
[ 2639.054437] usb 1-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 2639.054438] usb 1-1.4: Product: CDC/ACM Serial
[ 2639.054440] usb 1-1.4: Manufacturer: NuttX
[ 2639.054441] usb 1-1.4: SerialNumber: 0
[ 2639.074861] cdc_acm 1-1.4:1.0: ttyACM0: USB ACM device
[ 2639.074886] usbcore: registered new interface driver cdc_acm
[ 2639.074887] cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters
You may need to press ENTER 3 times before the NSH show up.
sdcard
Configures the NuttShell (nsh) and enables SD card support. The stm32f401rc-rs485 has an onboard microSD slot that should be automatically registered as the block device /dev/mmcsd0 when an SD card is present. The SD card can then be mounted by the NSH commands:
nsh> mount -t procfs /proc
nsh> mount -t vfat /dev/mmcsd0 /mnt
modbus_slave
Configures the NuttShell (nsh) and enables modbus in slave mode. This configuration enables a serial console on USART6. The RS-485 is connected to USART2. Follow below precedure to use modbus test aplication, you will need a USB to RS-485 converter to connect the board to a PC via RS-485.
NuttShell configuration:
Run modbus application at NSH:
nsh> modbus -help
USAGE: modbus [-d|e|s|q|h]
Where:
-d : Disable protocol stack
-e : Enable the protocol stack
-s : Show current status
-q : Quit application
-h : Show this information
nsh> modbus -e
PC Configuration:
Download and install mbpoll aplication:
sudo apt install mbpoll
Check which TTY USB port is being used by you USB to RS-485 converter:
sudo dmesg
[99846.668209] usb 1-1.3: Product: USB Serial
[99846.676313] ch341 1-1.3:1.0: ch341-uart converter detected
[99846.677454] usb 1-1.3: ch341-uart converter now attached to ttyUSB1
Run the mbpoll as below:
mbpoll -a 10 -b 38400 -t 3 -r 1000 -c 4 /dev/ttyUSB1 -R
At PC terminal you will see the mbpoll application receiving the random values generated by STM32F401RC-RS485 and transmitted over RS-485:
mbpoll 1.0-0 - FieldTalk(tm) Modbus(R) Master Simulator
Copyright © 2015-2019 Pascal JEAN, https://github.com/epsilonrt/mbpoll
This program comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it
under certain conditions; type 'mbpoll -w' for details.
Protocol configuration: Modbus RTU
Slave configuration...: address = [10]
start reference = 1000, count = 4
Communication.........: /dev/ttyUSB1, 38400-8E1
t/o 1.00 s, poll rate 1000 ms
Data type.............: 16-bit register, input register table
-- Polling slave 10... Ctrl-C to stop)
[1000]: 58080 (-7456)
[1001]: 0
[1002]: 0
[1003]: 0
-- Polling slave 10... Ctrl-C to stop)
[1000]: 6100
[1001]: 0
[1002]: 0
[1003]: 0
-- Polling slave 10... Ctrl-C to stop)
[1000]: 51010 (-14526)
[1001]: 0
[1002]: 0
[1003]: 0
-- Polling slave 10... Ctrl-C to stop)
[1000]: 12528
[1001]: 0
[1002]: 0
[1003]: 0
modbus_master
Configures the NuttShell (nsh) and enables modbus in master mode. This configuration enables a serial console on USART6. The RS-485 is connected to USART2. Follow below precedure to use modbusmaster test aplication, you will need a USB to RS-485 converter to connect the board to a PC via RS-485.
PC Configuration:
Download and install diagslave aplication from https://www.modbusdriver.com/diagslave.html.
Check which TTY USB port is being used by you USB to RS-485 converter:
sudo dmesg
[99846.668209] usb 1-1.3: Product: USB Serial
[99846.676313] ch341 1-1.3:1.0: ch341-uart converter detected
[99846.677454] usb 1-1.3: ch341-uart converter now attached to ttyUSB1
Run the diagslave as below:
sudo diagslave -a 10 -b 38400 /dev/ttyUSB1
At PC terminal you will see the diagslave application listening to address 10, notice that this address is configurable via MODBUSMASTER_SLAVEADDR:
diagslave 3.4 - FieldTalk(tm) Modbus(R) Diagnostic Slave Simulator
Copyright (c) 2002-2021 proconX Pty Ltd
Visit https://www.modbusdriver.com for Modbus libraries and tools.
Protocol configuration: Modbus RTU, frame tolerance = 0ms
Slave configuration: address = 10, master activity t/o = 3.00s
Serial port configuration: /dev/ttyUSB1, 38400, 8, 1, even
Server started up successfully.
Listening to network (Ctrl-C to stop)
Slave 10: readHoldingRegisters from 2, 1 references
.......
NuttShell configuration:
Run modbusmaster application at NSH:
NuttShell (NSH) NuttX-12.4.0
nsh> modbusmaster
Initializing modbus master...
Creating poll thread.
Sending 100 requests to slave 10
mbmaster_main: Exiting poll thread.
Modbus master statistics:
Requests count: 100
Responses count: 100
Errors count: 0
Deinitializing modbus master...
The application modbusmaster will send 100 requests, you can check on diagslave:
Server started up successfully.
Listening to network (Ctrl-C to stop)
Slave 10: readHoldingRegisters from 2, 1 references
Slave 10: readHoldingRegisters from 2, 1 references
Slave 10: readHoldingRegisters from 2, 1 references
Slave 10: readHoldingRegisters from 2, 1 references
Slave 10: readHoldingRegisters from 2, 1 references
Slave 10: readHoldingRegisters from 2, 1 references
Slave 10: readHoldingRegisters from 2, 1 references
lm75
Configures the NuttShell (nsh) over USB Serial (check usbserial configuration) and enables temperature sensor LM75. NSH commands:
nsh> lm75 -help
Usage: temp [OPTIONS]
[-n count] selects the samples to collect. Default: 1 Current: 100
[-h] shows this message and exits
nsh> lm75 -n 3
30.13 degrees Celsius
30.13 degrees Celsius
30.13 degrees Celsius
adc
Configures the NuttShell (nsh) over USB Serial (check usbserial configuration) and enables ADC 1 on channels 0 and 4. NSH commands:
nsh> adc -h
Usage: adc [OPTIONS]
Arguments are "sticky". For example, once the ADC device is
specified, that device will be re-used until it is changed.
"sticky" OPTIONS include:
[-p devpath] selects the ADC device. Default: /dev/adc0 Current: /dev/adc0
[-n count] selects the samples to collect. Default: 1 Current: 0
[-h] shows this message and exits
nsh> adc -n 2
adc_main: g_adcstate.count: 2
adc_main: Hardware initialized. Opening the ADC device: /dev/adc0
Sample:
1: channel: 0 value: 2684
Sample:
1: channel: 4 value: 2682
Currently there is a bug that causes the application to always read the same value for channel 0 and 4. If you want to read the value from channel 2, you will need to enable the config “ADC1 Scan Mode”.
dac
Configures the NuttShell (nsh) over USB Serial (check usbserial configuration) and enables PWM 3 on channel 1. Use pwm command on NSH to change dutty cycle, frequency and duration, use dac_out_2 to measure the output voltage. NSH commands:
nsh> pwm -h
Usage: pwm [OPTIONS]
Arguments are "sticky". For example, once the PWM frequency is
specified, that frequency will be re-used until it is changed.
"sticky" OPTIONS include:
[-p devpath] selects the PWM device. Default: /dev/pwm0 Current: NONE
[-f frequency] selects the pulse frequency. Default: 100 Hz Current: 100 Hz
[-d duty] selects the pulse duty as a percentage. Default: 50 % Current: 50 %
[-t duration] is the duration of the pulse train in seconds. Default: 5 Current: 5
[-h] shows this message and exits
nsh> pwm -d 50 -t 3
pwm_main: starting output with frequency: 50 duty: 00007fff
pwm_main: stopping output
qencoder
Configures the NuttShell (nsh) over USB Serial (check usbserial configuration) and enables Timer 3 on channels 1 and 2 to handle Quadrature Encoder. NSH commands:
nsh> qe -help
Usage: qe [OPTIONS]
OPTIONS include:
[-p devpath] QE device path
[-n samples] Number of samples
[-t msec] Delay between samples (msec)
[-r] Reset the position to zero
[-h] Shows this message and exits
nsh> qe -p /dev/qe0 -n 5 -t 100 -r
nsh: qe: too many arguments
qe_main: Hardware initialized. Opening the encoder device: /dev/qe0
qe_main: Resetting the count...
qe_main: Number of samples: 5
qe_main: 1. 0
qe_main: 2. 0
qe_main: 3. 4
qe_main: 4. 2
qe_main: 5. 2
Terminating!