UART Synchronisation issue LCM GUI display for NUCLEO-h743zi2 board

[sushma]

Dear Team,

I am interfacing Nucleo-h743zi2 board  with LCM display(GUI) through UART using Interrupt method.

I can transmit the data to LCM and it is displaying properly on the LCM display.

Now I am trying to send the commands from LCM display to STM controller. 

 I tried to press the button for many times on LCM display and observed sometimes it is triggering and sometimes not triggered). I think there is a  problem with synchronisation for receiving from LCM display to STM controller. I can see the events are triggered sometimes in debugging steps.

I tried to change the system clock to different values but it did not worked. Also I tried to increase the delays, decreasing delays at different places did not worked.

I tried to copy the receiving buffer into the other buffer and cleared the buffer. But this also does not worked.

Please find the below Receive function for your reference:

extern uint8_t data_u[100];
uint8 j, max;

uint8 ReadSerialByte( uint8 *data)

{

if (max == 0) {

max = huart2.RxXferSize - huart2.RxXferCount;

if ( max == 0 ) return 0;

}

if (j >= max && max > 0) {

j=0;

max=0;

HAL_UART_Receive_IT(&huart2, data_u, 100);

return 0;

}

*data=data_u[j];

j++;

   return 1;

}/* ReadSerialByte */

It is mentioned in LCM document as follows:

your serial receive function should timeout after 0.1s (= SERIAL_ATOMIC_TIMEOUT defined in "config.master.h").

All other timeouts must be multiples of this (see "config.master.h" again):

#define SERIAL_ATOMIC_TIMEOUT 1   /*!< in tenth of seconds (default 0.1s); the
                                       timeout of the serial port should be
                                       configured to the same time (0.1s) */
#define SERIAL_NORMAL_TIMEOUT 20  /*!< in tenth of seconds (default 2s), must
                                       be a multiple of the
                                       SERIAL_ATOMIC_TIMEOUT */
#define SERIAL_FLASH_TIMEOUT  600 /*!< in tenth of seconds (default 60s), must
                                       be a multiple of the
                                       SERIAL_ATOMIC_TIMEOUT */

For every "normal" command you should receive a response package after 2s (= SERIAL_NORMAL_TIMEOUT).

You have to wait for the response befor sending the next command.

Please guide me to know how we can resolve the synchronisation issues by using above LCM information .

Do I need to use timer for 0.1sec to receive function. If yes could you please help me to know how we can write it in code.

[sushma]

@Tesla DeLorean 

Thank you for your reply.

I think, There is request - response pair in serial communication. I tried with clearing the buffer. but, It did not worked.

Please let me know whether It will be a good idea to implement my own ring/fifo buffering methods  in this case.

[Andrew Neil]

---

@sushma wrote:

Could you please help me to know how we can check the actual speeds on the wires?

---

Measure the bit widths on your oscilloscope 

[Pavel A.]

@sushma I mean the normal default HAL 1ms timer tick, often it is the ARM systick but can be one of STM32 timers. You just call HAL_GetTick to get the wait start time, then repeat HAL_GetTick in the main loop to detect timeout (for example, if (HAL_GetTick() - start_time > 2000) { /*timeout! */ }

No need to be precise there.

[sushma · Accepted solution]

Dear All,

Thank you so much for your Guidence.

I tried with polling method and receiving each byte for 100ms timeout instead of receiving with interrupt method. It worked for me. 

Now, I do not have synchronisation issues.

Regards,

Sushma