UART HW flow control bugs

RE: UART HW flow control bugs

abhipray — Wed, 30 May 2018 02:49:25 GMT

Oh wow, thanks for that. Any ideas on possible solutions?

RE: UART HW flow control bugs

hmolesworth — Wed, 30 May 2018 02:47:11 GMT

I posted this elsewhere, but offhand forget where. I think that the flow control is incorrectly inverted in the hardware for use with a UART-USB (typically 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). Hope this helps.

RE: UART HW flow control bugs

abhipray — Wed, 30 May 2018 02:15:17 GMT

Any updates on this? We're still seeing this issue.

RE: UART HW flow control bugs

abhipray — Tue, 21 Nov 2017 18:21:57 GMT

I have not tested this on the DK. The UART-USB bridge is an SI Labs CP-2102. I can try to upload some example code that reproduces the problem.

RE: UART HW flow control bugs

Sigurd — Mon, 20 Nov 2017 16:39:52 GMT

Hi,

Do you have this issue when using the nrf52832-DK ?
Since this is not a eval kit/ DK, what kind "UART-USB bridge" are you using ?
Could you upload some example code / project, so that we can reproduce the issue here ?

RE: UART HW flow control bugs

abhipray — Mon, 20 Nov 2017 15:58:55 GMT

I am not using an eval kit. Would this same problem show up if I use an external Segger j-link probe for programming?

RE: UART HW flow control bugs

Krzysztof Chruscinski — Mon, 20 Nov 2017 14:05:52 GMT

Hi,

it maybe related to the fact how Segger chip determines if HWFC should be used.