pigpio
pigpio copied to clipboard
fivdi
Bitbanged UART?
Very nice project, but it lacks the bitbanged (software) serial read and write function, which the c and python libraries have. This is a very helpful feature which makes it possible to connect more UART devices to the rpi on normal gpio pins. Is there any chance it will be implemented?
Implementation of the waveform functions is being discussed in #38. I'm happy to look at implementing the gpioSerialRead* functions once I'm done with waveforms.
@AnthonyMyatt This would be fantastic. A pull request for this would be excellent. Perhaps a second PR rather than together with the waveforms PR?
Given that the Raspberry Pi 4 supports up to 6 hardware UARTs, the need for adding bitbanged support for UARTs is not necessarily what it was in the past.
@fivdi I have included all the necessary functions as I was working on the wave functions. Because I need the serial functions in some projects on a Raspberry Pi 3B+, I would finish the work anyway in my fork. Would you still be interested in merging even though it's no longer as important?
@Rogerrrrrrrs
Would you still be interested in merging even though it's no longer as important?
Sure :smile:
Bitbanged serial would solve access to 9 bit Raymarine Seatalk 1 data very nicely - @Rogerrrrrrrs how far is your work?
@tkurki I'm sorry I kinda forgot about this one.
I have implemented all serial related methods in my fork and used them for quite a while now.
I just had one problem for which I could not come up with a good solution. To make life easier for the users of this library, I intended to create a gpio.on("serialdata") event.
If I remember correctly, to avoid missing any serial data, the pigpio C library requires to frequently call gpioSerialRead and retrieve the read data and free up the buffer which is internally used. However the pigpio C library does not offer a callback function when the buffer is full or when serial data is received.
In my personal use case I know that every 500ms serial data is received, so I can use an interval to frequently read the received data.
But I don't think an interval would be a good solution for this library.
I have also tried to create something with the alert and interrupt events but I think there where other problems so I discarded these ideas.
The other option would be to just implement the serial methods as they are in the pigpio C library, but in order to live up to the high standard of this library, I think this library needs something like a gpio.on("serialdata") event if the serial methods are implemented, otherwise we would just pass this problem to the user.
I don't think that I have time to take a look at this again in the near future, but if someone has an idea to solve this problem please let me know.
@fivdi what are your thoughts about this?
One extremely blunt solution would be to make the interval part of the library and allow configuration as to how often it is run.
@fivdi what are your thoughts about this?
I haven't worked with the serial functions available in the pigpio C library and can't say what could be used to avoid polling at a high rate. I would have thought that alerts could be used but if you have already tried it and they don't work then I guess you're right.
I think this library needs something like a gpio.on("serialdata") event if the serial methods are implemented, otherwise we would just pass this problem to the user.
I agree with this statement. I also think that polling at a high rate will not make users happy.
@tkurki you could try @Rogerrrrrrrs fork to see if it works for you.
I'll go ahead and close this as the Raspberry Pi 4 supports up to 6 hardware UARTs and the need for adding bitbanged support for UARTs is not necessarily what it was in the past.