Serial driver Transmission End Topic is solved

[alexblack]

Hi.
I used ChibiOS 17.6.x and after updating to the latest version I was found that changes in SERIAL drivers is affect to my program.
I have function to send 1 (ONE) byte over serial driver is SPI mode.

Code: Select all

/** ------------------------------------------------------------------------ **
 * \brief       Setting the given value to potenciometer
 * \param[in]   value - given value
 * ------------------------------------------------------------------------- */
void PGA_Class::set_value(char value) {

  // Start the driver
  static const SerialConfig pga_serial_cfg = {
  4500000,
  0,
  USART_CR2_MSBFIRST | USART_CR2_CLKEN | USART_CR2_LBCL, // | USART_CR2_CPHA | USART_CR2_CPOL
  0  
  };
  sdStart(&PGA_SERIAL_DRIVER, &pga_serial_cfg);
  // RX not used
  PGA_SERIAL_DRIVER.usart->CR1 &= ~USART_CR1_RE;
  
  // Register event listener to receive USART events
  event_listener_t el_sd;
  chEvtRegisterMask(chnGetEventSource(&PGA_SERIAL_DRIVER), &el_sd, 128);
  
  // Accert the CS line
  palClearPad(cs->port, cs->pin_n);
  
  // write to register  
  sdPut(&PGA_SERIAL_DRIVER, value);
  
  // wait the end of transmission
  for (;;) {
    eventmask_t m = chEvtWaitOneTimeout(128, MS2ST(100));
    if (m == 0) break;
  
    // event of the UART
    eventflags_t flags = chEvtGetAndClearFlags(&el_sd);
    if (flags & CHN_TRANSMISSION_END)
      break;
  }
   
  // Release the CS
  palSetPad(cs->port, cs->pin_n);
  
  // Unregiister
  chEvtUnregister(chnGetEventSource(&PGA_SERIAL_DRIVER), &el_sd);
  
  // Stop the driver
  sdStop(&PGA_SERIAL_DRIVER);
}

When I used before the function was success to wait end of transmission, but now it exit with timeout.
I looking to the change history and found that there was this changes:

What was the need to really change this behavior?

[Giovanni]

The idea is that the flag should be raised only if the TCIE interrupt is enabled.

TCIE is enabled when a transmission is started and cleared when it is completed and the event has been triggered.

Giovanni

[alexblack]

In my case (one byte transsmission) the TC flag is raised before the TXE flag is served and thus do not generate TC interrupt.
I tried send 2 bytes - new code work well. But what to do with one byte. I need to wait the end of transmission to deactivate the CS line.

[Giovanni]

You could try, in the LLD, to set USART_CR1_TCIE in those notifyX() functions and remove it from serve_interrupt(), this should fix that specific problem.

Code: Select all

static void notify5(io_queue_t *qp) {

  (void)qp;
  UART5->CR1 |= USART_CR1_TXEIE | USART_CR1_TCIE;
}

Let me know how this goes, I would make the change in repository too.

Giovanni

[alexblack]

I thinking that there will be errornous TC events when there are the gaps between the chars if the baud rate is fast enough or if the system has large load.

[alexblack]

I tried your suggestion to notifyX function and it works.
The DEBUG OUT function is:

Code: Select all

PGA: > set value 127
PGA: > m = 0080
PGA: > flags = 0018
PGA: > end

Was before:

Code: Select all

PGA: > set value 127
PGA: > m = 0080
PGA: > flags = 0008
PGA: > m = 0000
PGA: > timeout

[Giovanni]

Moving this in "bug reports", it is definitely a problem in the driver.

Giovanni

[Giovanni]

Fixed as bug #958.

Giovanni