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UART question.
Posted: Fri Mar 02, 2018 1:11 pm
by rew
Code: Select all
/**
* @brief Stops any ongoing receive operation.
* @note Stopping a receive operation also suppresses the receive callbacks.
*
* @param[in] uartp pointer to the @p UARTDriver object
*
* @return The number of data frames not received by the
* stopped receive operation.
* @retval 0 There was no receive operation in progress.
*
* @api
*/
What happens when I start calling "uartStopReceive" and right at that moment, the buffer fills, i.e. 0 bytes remain to be put into the buffer?
Re: UART question.
Posted: Fri Mar 02, 2018 1:44 pm
by Giovanni
It reads the DMA counter register, so you get zero.
Giovanni
Re: UART question.
Posted: Sun Mar 04, 2018 1:18 pm
by rew
Which is the same zero you would get when no operation was started. Wouldn't it be much better to have the return value be -1 when no operation was started? Choosing an "error code" from the range of valid "normal" return values is not such a good idea.
Re: UART question.
Posted: Sun Mar 04, 2018 3:59 pm
by Giovanni
Moving in "change request".
Giovanni
Re: UART question.
Posted: Tue Mar 06, 2018 3:21 pm
by rew
FYI,
As with an example I found somewhere, (probably in haltest), my mainloop simply first stops the ongoing transfer, starts a new transfer in the "double buffer", and then processes whatever it got. So the first time around the loop, I get a "0" (no transfer started), which to the processing code means "got a full buffer!".
You might say: well first start the transfer then! Yeah. I can copy the code to start the first transfer. But then I've duplicated code leading to the real possibility of fixing a bug in one of them and not in the other.
When I started this thread, this was a bug, waiting to happen. It happened. My logfile now has:
Code: Select all
...
001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00200 67 45 23 01 46 3d 36 0b fa ff ff ff 00 00 00 00
.. my data...
Re: UART question.
Posted: Wed Mar 07, 2018 10:53 am
by Giovanni
Hi,
I fixed it as bug #925 in trunk and 18.2.x.
Giovanni