Software UART and WAITKEY - Exit if no incoming data

davidmoran · Joined: 31 Dec 2019 Posts: 14

This may have been answered before, but I couldn't' find it in a search.

I guess I am looking for the best way to send and receive binary data over a software serial port.

I added a software UART to an ATMEGA2560 circuit on some unused pins using the OPEN COM...(#4) command. It works fine, and I can get my serial data in and out. However, the only BASCOM command to receive the input data from a software defined UART appears to be the WAITKEY command, and this will wait forever if there is no incoming serial data. I need to be able to exit the WAITKEY command if no data is received after I request it, after some timeout. Do any of the other serial commands like ISCHARWAITING work with the software UART?

I have done some testing, and it appears that if the software UART input is LOW, the WAITKEY will proceed, and return a value of $00, with or without the $TIMEOUT command. However, if the software UART input is HIGH, then the WAITKEY will hang forever. I have tried adding the $TIMEOUT = 1000000 command, but it does not seem to prevent this issue. Perhaps this is because of the Port Number I opened?

Using INKEY or GET instead of WAITKEY seems to give the same results. I cannot use INPUT, because the input is binary data, without CR or LF.

I looked at the newer SERIN and SEROUT commands, but they are only for Strings as well, and I'm not sure if they provide a timeout feature either. Also, the Baud rate calculation seems to be pretty far off, at least in version 2.0.8.2. Perhaps there is a way to use strings with binary data, but since $00 is in the data, I think that would terminate the string.

Any other ideas on how to accomplish this would be appreciated.

Thanks,
Dave

(BASCOM-AVR version : 2.0.8.2 , Latest : 2.0.8.5 )

EDC · Joined: 26 Mar 2014 Posts: 971

From the Help: "$Timeout - Enable timeout on the hardware UART and software UART."

Works like a charm. Why don`t you upgrade Bascom into 2085?

BTW. All four USARTS from Mega2560 you have used already or this is unefficient design?

davidmoran · Joined: 31 Dec 2019 Posts: 14

Thank you for the information. I am switching from a dumb sensor with a TTL logic interface to a smart sensor with a serial interface while using the same IO pins, that is why I need a software-defined UART. The other hardware UARTs are also all in use.

I was using the slightly older version of BASCOM because we have a development environment freeze on this project. I have experimented with the 2.0.8.5 version with similar results.

With the $TIMEOUT command added, I think it is indeed moving past the WAITKEY command with no data input, and with the serial input pin either HIGH or LOW. However, I still see some cases where it appears to hang up, so I am trying to resolve what is happening there. Thanks for the help.

enniom · Joined: 20 Oct 2009 Posts: 537

DavidMoran,

Difficult to answer your question without a Code Example from you that shows (or occasionally shows) the problem.

E