nRF51822 uart flow control

RE: nRF51822 uart flow control

Christopher — Tue, 15 Dec 2015 12:42:20 GMT

Thank you @Aryan, glad to hear that this bug is now fixed. The HAL and low level drivers have changed a lot in SDK10. I will try the new UART driver with HFC soon.

RE: nRF51822 uart flow control

Susheel Nuguru — Tue, 15 Dec 2015 12:33:30 GMT

I am sorry Christopher, this is actually fixed in SDK10, I will remove this from the list.

RE: nRF51822 uart flow control

Susheel Nuguru — Tue, 24 Nov 2015 07:13:59 GMT

Unfortunately :(

RE: nRF51822 uart flow control

Christopher — Mon, 23 Nov 2015 21:23:10 GMT

Still a bug in the SDK10 :( devzone.nordicsemi.com/.../

RE: nRF51822 uart flow control

Susheel Nuguru — Fri, 18 Sep 2015 10:18:52 GMT

yes, i see that it is not the best solution and has opened up ways to deadlock the reads. I think the best solution is along with your fix, we should add below

whenever app_fifo_get is called, if the fifo was full, empty one slot to user byte address. Then read the EVENTS_RXDRDY status, and if set, new read on RXD and clear RXRDY event. This will make sure that the last ignored read will be done here.

Also the clearing of event should be done like this inside UART0_IRQHandler

if (FIFO_LENGTH(m_rx_fifo) <= m_rx_fifo.buf_size_mask)
{
    err_code = app_fifo_put(&m_rx_fifo, (uint8_t) NRF_UART0->RXD);

    // Clear UART RX event flag
    NRF_UART0->EVENTS_RXDRDY = 0;    
}

RE: nRF51822 uart flow control

Christopher — Thu, 17 Sep 2015 11:01:25 GMT

FYI, the RXD register is not any more read each time the UART0 ISR occurs. To avoid deadlock and to resume to UART stream (to active the CTS again), the app_uart_get function must also be updated: the RXD register must be read if an overflow occurs.

I am not sure if my patch is the best solution, but now you are aware of this bug. Thank you @Aryan to add it on the list.

RE: nRF51822 uart flow control

Susheel Nuguru — Thu, 17 Sep 2015 09:56:21 GMT

I have tested your fix and it worked for me too. I have to include this in the known bugs of SDK 9.0

RE: nRF51822 uart flow control

Christopher — Thu, 09 Jul 2015 14:05:41 GMT

The latest app_uart_fifo file (included in the SDK 9) contains a bug. 3 bytes where systematically lost (even with HFC) because of a bug in the UART0_IRQHandler function.

Be sure that the in the UART0_IRQHandler function you check that the RX FIFO is not full before reading the RXD register or some bytes will be lost !

if (FIFO_LENGTH(m_rx_fifo) <= m_rx_fifo.buf_size_mask)
    err_code = app_fifo_put(&m_rx_fifo, (uint8_t) NRF_UART0->RXD);
    // ...

I successfully transferred a 2MB file over a UART link (115'200 bauds) without any error, using the new chip revision with the six-byte buffer.

RE: nRF51822 uart flow control

Ole Morten — Fri, 13 Sep 2013 11:43:11 GMT

Beware that there is a bug in the nrf51_bitfields.h file, in that the value for 921600 baud rate is incorrect. It should therefore not be used, and if you do, the actual baud rate might be different from expected. See this question for information on baud rate calculation. Does using a somewhat different baud rate help on this problem?

If not, this could also be due to the peer device not reacting quick enough when RTS is deasserted, and by that overflowing the buffer. This is a problem that I believe has been seen internally. The upcoming, new chip revision therefore features a six-byte buffer to alleviate this. It could therefore also be worth it to try getting hold of this revision and test whether you see different behavior. Please contact the sales manager for your area for more information on this. If you don't have his contact information, please send me a private message with your location.