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UART serial Flow Control

Posted: Fri Jul 26, 2019 1:31 am
by N5BOC
I have read where you can enable FLOW CONTROL on the pi UART by assigning some GPIO pins to it. Now I realize the MMDVM's don't make use of Flow Control, but I just wonder if by chance it is active on the serial UART when operating in Pi Star. I'm wanting to glue an FPGA in between the PI and the MMDVM to see if I can implement some type of buffer so that no bits are lost.

Thanks so much.
Dave
N5BOC

Re: UART serial Flow Control

Posted: Fri Jul 26, 2019 3:46 am
by KE7FNS
N5BOC wrote: Fri Jul 26, 2019 1:31 am I have read where you can enable FLOW CONTROL on the pi UART by assigning some GPIO pins to it. Now I realize the MMDVM's don't make use of Flow Control, but I just wonder if by chance it is active on the serial UART when operating in Pi Star.
No, its not active on a RPi, and its not active on MMDVM's that use a STM32 processor either. In order to make it active, you'd have to enable it on both sides, in the RPi, and on the MMDVM firmware. Its possible, but its a waste of time and effort.
N5BOC wrote: Fri Jul 26, 2019 1:31 am I'm wanting to glue an FPGA in between the PI and the MMDVM to see if I can implement some type of buffer so that no bits are lost.
There are NO bits being lost, if there were bits being lost things wouldn't work correctly. Messages between the RPi and the MMDVM would be corrupted left and right, and that just isn't the case.

Adding another link in the chain of communications is just going to add a delay. If you are going to bother putting a FPGA in there, you might as well just have it do all processing that the STM32 does.

Re: UART serial Flow Control

Posted: Sun May 23, 2021 2:02 am
by N5BOC
You are right. Offloading the work done by the STM32 into an FPGA would be the correct thing to do instead of gluing something in between them.

Re: UART serial Flow Control

Posted: Fri Jun 04, 2021 6:46 pm
by MW0MWZ
I don't believe that bits are lots between the Pi and the modem (be it USB or UART GPIO pins).
the BER or Loss that we see can be either decode issues, or network issues, is this what you were looking to fix ?