Hi,
unfortunately I can’t get UART communication working at higher baud rates (>115200 for the NUCLEO-WL55JC1 and >76800 for the DISCO-L072CZ-LRWAN1).
When I use higher baud rates, some bytes are missing.
I use this program to verify the integrity of the communication using a single board, i.e. the UART TX pin is connected to the UART RX pin.
#include "mbed.h"
// See this table for common baud rates:
// https://lucidar.me/en/serialib/most-used-baud-rates-table/
// For the NUCLEO board, I can go up to 115200 bauds without errors
// For the DISCO board, I can go up to 76800 bauds without errors
// const int BAUD_RATE = 76800;
const int BAUD_RATE = 115200;
// For NUCLEO board
// Note: You need to use STM32CubeProgrammer to flash the program to the board.
// const PinName TX_PIN = PB_6;
// const PinName RX_PIN = PB_7;
// For DISCO board
const PinName TX_PIN = PA_9;
const PinName RX_PIN = PA_10;
const int BUFFER_SIZE = 32;
// Connect TX_PIN with RX_PIN (loopback) and also GND if using two boards
BufferedSerial serial_port(TX_PIN, RX_PIN, BAUD_RATE);
uint8_t tx_buffer[BUFFER_SIZE];
uint8_t rx_buffer[BUFFER_SIZE] = {0};
void init_tx_buffer() {
for (int i = 0; i < BUFFER_SIZE; i++) {
tx_buffer[i] = i;
}
}
bool are_buffer_equal(const uint8_t *buffer_1, const uint8_t *buffer_2,
size_t buffer_size) {
return memcmp(buffer_1, buffer_2, buffer_size) == 0;
}
void test_uart() {
while (!serial_port.writable()) {
// Wait for serial port to be ready to write
}
int sent_bytes_count = serial_port.write(tx_buffer, BUFFER_SIZE);
printf("Sent %d bytes\n", sent_bytes_count);
ThisThread::sleep_for(2s);
while (!serial_port.readable()) {
// Wait for serial port to be ready to read
}
int read_bytes_count = serial_port.read(rx_buffer, BUFFER_SIZE);
printf("Read %d bytes\n", read_bytes_count);
if (read_bytes_count != BUFFER_SIZE) {
printf("Error: Expected to read %d bytes\n", BUFFER_SIZE);
return;
}
if (are_buffer_equal(rx_buffer, tx_buffer, BUFFER_SIZE)) {
printf("SUCCESS: RX buffer is equal to TX buffer\n");
} else {
printf("ERROR: RX buffer is different than TX buffer\n");
}
}
int main() {
printf("Starting UART test...\n");
init_tx_buffer();
ThisThread::sleep_for(1s);
while (true) {
test_uart();
}
}
So far, I’ve tried:
- Using different UARTs (UART1 and UART2) → no effect
- Using a deep sleep lock → no effect
- Using a different compile profile → Release and Develop seem to be a bit more reliable than Debug
- Using UnbufferedSerial instead of BufferedSerial ->no effect
- Increasing the TX and RX buffer sizes for BufferedSerial → no effect
- Tried different compilers (GCC_ARM vs ARMC6) → no effect
- Using two DISCO boards for UART communication instead of a single one → no effect
Open questions:
- Could this be related to Low-Power UART? For the DISCO board I use pins PA_9 and PA_10.
As far as I can tell from PeriphalPins.c, LPUART it is disabled by default and the proper UART is used, right?
//*** SERIAL ***
MBED_WEAK const PinMap PinMap_UART_TX[] = {
{PA_0, UART_4, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_USART4)},
{PA_2, UART_2, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF4_USART2)}, // Connected to STDIO_UART_TX
// {PA_2, LPUART_1,STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_LPUART1)}, // Connected to STDIO_UART_TX
{PA_9, UART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF4_USART1)},
{PA_14, UART_2, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF4_USART2)},
{PA_14_ALT0, LPUART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_LPUART1)},
{PB_3, UART_5, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_USART5)}, // Connected to RADIO_SCLK
{PB_6, UART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF0_USART1)},
{PB_10, LPUART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF4_LPUART1)},
{PB_11, LPUART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF7_LPUART1)},
{PC_1, LPUART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_LPUART1)}, // Connected to RADIO_ANT_SWITCH_TX_BOOST
{NC, NC, 0}
};
MBED_WEAK const PinMap PinMap_UART_RX[] = {
{PA_1, UART_4, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_USART4)}, // Connected to RADIO_ANT_SWITCH_RX
{PA_3, UART_2, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF4_USART2)}, // Connected to STDIO_UART_TX
// {PA_3, LPUART_1,STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_LPUART1)}, // Connected to STDIO_UART_TX
{PA_10, UART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF4_USART1)},
{PA_13, LPUART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_LPUART1)},
{PA_15, UART_2, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF4_USART2)}, // Connected to RADIO_NSS
{PB_4, UART_5, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_USART5)}, // Connected to RADIO_DIO_0
{PB_7, UART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF0_USART1)},
{PB_10, LPUART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF7_LPUART1)},
{PB_11, LPUART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF4_LPUART1)},
{PC_0, LPUART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_LPUART1)}, // Connected to RADIO_RESET
{NC, NC, 0}
};
Any help is very much appreciated!
