Hey folks. So for a beginner DIY fixed-wing flight controller, I am trying to incorporate servo values from an external receiver via SBUS [by FrSky (0-> Low, 1-> High; contrary to the standard SBUS by Futaba)] into my software.
I found a good amount of code for the sum frame decoding, but appear to not receive any UART communication at all from the receiver.
A UART RX Callback function generates an interrupt whenever there's a new frame received. The function is supposed to write a message via another UART to my Putty-terminal (which works fine), upon calling.
Further into it, the SBUS frame gets torn apart and the individual channel values generated - but I'm not even at this stage, and by the looks of it, it should work fine. My code:
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
uint16_t failsafe_status;
uint8_t buf[25];
uint16_t CH[18];
int lenght=0;
uint16_t USB_Send_Data[]={0};
char msg[25];
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart1)
{
sprintf(msg, "FRAME AQCUIRED\r\n");
HAL_UART_Transmit(&huart2, (uint8_t*)msg, strlen(msg), HAL_MAX_DELAY);
if (buf[0] == 0x0F) {
CH[0] = (buf[1] >> 0 | (buf[2] << 8)) & 0x07FF;
CH[1] = (buf[2] >> 3 | (buf[3] << 5)) & 0x07FF;
CH[2] = (buf[3] >> 6 | (buf[4] << 2) | buf[5] << 10) & 0x07FF;
CH[3] = (buf[5] >> 1 | (buf[6] << 7)) & 0x07FF;
CH[4] = (buf[6] >> 4 | (buf[7] << 4)) & 0x07FF;
CH[5] = (buf[7] >> 7 | (buf[8] << 1) | buf[9] << 9) & 0x07FF;
CH[6] = (buf[9] >> 2 | (buf[10] << 6)) & 0x07FF;
CH[7] = (buf[10] >> 5 | (buf[11] << 3)) & 0x07FF;
CH[8] = (buf[12] << 0 | (buf[13] << 8)) & 0x07FF;
CH[9] = (buf[13] >> 3 | (buf[14] << 5)) & 0x07FF;
CH[10] = (buf[14] >> 6 | (buf[15] << 2) | buf[16] << 10) & 0x07FF;
CH[11] = (buf[16] >> 1 | (buf[17] << 7)) & 0x07FF;
CH[12] = (buf[17] >> 4 | (buf[18] << 4)) & 0x07FF;
CH[13] = (buf[18] >> 7 | (buf[19] << 1) | buf[20] << 9) & 0x07FF;
CH[14] = (buf[20] >> 2 | (buf[21] << 6)) & 0x07FF;
CH[15] = (buf[21] >> 5 | (buf[22] << 3)) & 0x07FF;
if (buf[23] & (1 << 0)) {
CH[16] = 1;
} else {
CH[16] = 0;
}
if (buf[23] & (1 << 1)) {
CH[17] = 1;
} else {
CH[17] = 0;
}
// Failsafe
failsafe_status = SBUS_SIGNAL_OK;
if (buf[23] & (1 << 2)) {
failsafe_status = SBUS_SIGNAL_LOST;
}
if (buf[23] & (1 << 3)) {
failsafe_status = SBUS_SIGNAL_FAILSAFE;
}
// SBUS_footer=buf[24];
}
}
/* USER CODE END 0 */This snippet is not mine, and I've got the feeling that the translation from the values into the buffer is missing. Could that be? If so, how would that look? To keep things simple I would like to avoid DMA in the beginning.
The while-loop is basically just the channel values 1-6 being printed to the serial terminal repeatedly.
CONCLUSION: Since the serial communication itself works, but neither gets any values nor notifies for a new frame, I think the issue lies within the SBUS -> UART part of it. Means, the Callback doesnt get executed for whatever reason. Additionally, here's my .ioc:
Iv'e tried it with 9 or 8 bits word length, but that doesnt change anything. Since FrSky is using the Inverted-SBUS, which is inverted itself (0->H, 1->L), I figured the data polarity is correct aswell as the jumper wires and config settings on the RX.
Regarding the transfer to the buffer AND/OR the Callback, what are your thoughts?
A small success:
After doubling the rx buffer up to 50 bytes and looking for the start flag, then transfering the index of the flag in this buffer to the SBUS-Yes/No?-Check I was able to achieve pretty regular lock-ons directly after resetting the MCU by hand. Unfortunately only then. But hey.
It is far from perfect still, but better than yesterday. Tomorrow I will have the time to read deeper into what you kindly suggested to further improve my concept; Interrupts especially. Any ideas for further lecture?
@StefanRinside my while-loop:
This could be an easy and combined with other strategies fast way to combat shifting.
