Receiving speed with UART

[garivin]

I have to receive a desired speed that is sent from the TX code, and receive it into the RX code of another different STM32 board that is connected to a Maxon 251601 motor, for it to work.

If i write for example MC_ProgramSpeedRampMotor1(1500,2000) directly in the board that it is connected to the motor it works good.

The problem that I have is that I try to send this from the transmiter board:

char tx_buff[32];

int velocidad = 1500;

while (1)
{
   int len = sprintf(tx_buff, "SPD%d\n", velocidad);
   HAL_UART_Transmit(&huart2, (uint8_t*)tx_buff, len, HAL_MAX_DELAY);
   HAL_Delay(1000);
}

And the receiver has this in the main:

char rx_buff[32];

int duration = 5000;

while (1)

{

HAL_UART_Receive(&huart2, (uint8_t*)rx_buff, 8, HAL_MAX_DELAY);

char *ptr = strstr(rx_buff, "SPD");
if (ptr != NULL)
{
  int velocidad = atoi(ptr + 3);
  MC_StartMotor1();
  MC_ProgramSpeedRampMotor1(velocidad, duration);
}

I was trying for it to receive "SPD1500\n" inside the rx_buff, to make the motor move. The strange thing is that while I was trying to receive it, it actually worked once, but the motor didn't move, so when I tried it again it didn't receive anything, even with the same code. I have heard that it could have been only luck that the transmiter and receiver were sincronized at the same moment, but I could not do it again.

Do you think that I should change something in the code to receive the speed and make the motor move using the MC_ProgramSpeedRampMotor(speed,time), or does this issue come from somewhere else?

[Pavel A.]

Your code is a bit naive. Please search for examples of buffered, asynchronous and receive and transmit. Unlike Arduino or other libraries, the STM32 HAL library does not provide buffering.

[garivin]

I have looked for simple examples, but non of them send this type of message. I can not find  a tx, rx about a speed that will be transmited into a motor. I have been able to send buffers but nothing like this.

[Andrew Neil]

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@garivin wrote:

but non of them send this type of message. 

---

Really?

It's just a simple text string "SPD1500\n"

As far as the UART goes, that's no different to sending "Hello, World\n"

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@garivin wrote:

I can not find  a tx, rx about a speed that will be transmited into a motor. .

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That's entirely irrelevant to the UART.

As far as the UART goes, it's all just a string of characters.