Couldn't use flow control on 52832

RE: Couldn't use flow control on 52832

hmolesworth — Wed, 23 May 2018 01:59:16 GMT

I think that the flow control is incorrectly inverted in the hardware for use with an FTDI part connected to a PC. The complication starts with the meaning of "flow control", as there are at least two versions, the traditional modem CTS/RTS usage and the more modern CTS/RTS handshake. I added these comments to clarify this:

/**@brief  Function for initializing the UART module.
 * Traditional Modem Flow Control
 * If flow control is enabled, a transmission will be automatically suspended when CTS is deactivated and
 * resumed when CTS is activated again.
 * A byte that is in transmission when CTS is deactivated will be fully transmitted before the transmission is
 * suspended.
 * nRF52 DTE Output pin to DCE - asserts to request transmit
 * nRF52 DTE Input pin from DCE - asserts to allow transmit
 *
 * Hardware Flow Control
 * "RTS/CTS handshaking" the DTE asserts RTS whenever it is ready to receive data from the DCE, and the DCE
 * asserts CTS whenever it is ready to receive data from the DTE. Unlike the original use of RTS and CTS with
 * half-duplex modems, these two signals operate independently from one another.
 * nRF52 DTE Output pin to DCE - asserts to allow DCE to transmit
 * nRF52 DTE Input pin from DCE - asserts to allow nRF52 DTE transmit
 */

The nRF52 hardware supports the traditional modem usage, but the software is written for the more recent CTS/RTS handshake which requires an inverter for proper operation as the nRF52832 does not allow configuring active-high/low operation unless the lines are driven manually (the logic is inverted so does not work correctly)

RE: Couldn't use flow control on 52832

Vidar Berg — Tue, 22 May 2018 09:13:49 GMT

The FTDI chip is well known, and would not expect it to have this issue. Could it be that you have a counterfeit chip? Found this blog post which indicates that this might be a common problem: https://hackaday.com/2014/02/19/ft232rl-real-or-fake/

RE: Couldn't use flow control on 52832

John — Tue, 22 May 2018 08:05:38 GMT

Thank you for your help.

I use our board to connect to the uart on the PCA10040 to work with flow control, it's OK now. Is there any USB to serial UART module that you could introduce to us?

RE: Couldn't use flow control on 52832

Vidar Berg — Tue, 22 May 2018 07:30:50 GMT

Have you tried 9600? Also, have you tried different PCs and terminal clients? It sounds like the problem might be on the FT232RL/PC side. Think you need to use a scope to confirm that.

RE: Couldn't use flow control on 52832

John — Sat, 19 May 2018 08:17:10 GMT

I have enabled the HF crystal and I also have tried 115200 baudrate, but I still get the 0x04 error.

RE: Couldn't use flow control on 52832

Vidar Berg — Fri, 18 May 2018 08:28:08 GMT

0x4 means that there was a packet framing error (UARTE->ERRORSRC):

A valid stop bit is not detected on the serial data input after all bits in a character have been received.

If you have a logic analyzer/scope I would suggest to probe the RX line to confirm whether the stop bit is missing or not. You could also try to enable the HF crystal while receiving, that will increase the baudrate accuracy.

API calls to request/release HFXO:

sd_clock_hfclk_request

sd_clock_hfclk_release

RE: Couldn't use flow control on 52832

John — Wed, 16 May 2018 07:05:00 GMT

It occurs during transfer. The error reason is 0x04, what does it mean?

RE: Couldn't use flow control on 52832

Vidar Berg — Tue, 15 May 2018 12:45:08 GMT

Does the communication error occur during transfer, or does it fail before that? Wondering if it could be related to power-up or IO configuration. You can check the error source in NRF_UARTE->ERRORSRC.

RE: Couldn't use flow control on 52832

John — Tue, 15 May 2018 11:57:57 GMT

Hi,

I'm sorry. Yes, I have use APP_UART_FLOW_CONTROL_ENABLED to enable flow control. For our board, it's need to enable hardware flow control in the UART terminal on PC when work with the USB to serial UART module, but it's no need to do it for PCA10040. Now the UART could receive and send less data.

However, I found a problem. The UART would return an error APP_UART_COMMUNICATION_ERROR in the uart_event_handle function when I use PC to send a document, which is about 20k bytes. If I program the same code to PCA10040, it wouldn't get the error. What reason would be?

RE: Couldn't use flow control on 52832

Vidar Berg — Tue, 15 May 2018 11:30:04 GMT

Hi,

Please confirm whether you observe this problem before or after enabling flow control. You said that you enabled flow control, but APP_UART_FLOW_CONTROL_DISABLED implies that you are disabling it?