UART baudrate 100000

[swiftimundo]

I'm trying to use an RC receiver's SBUS with Pi Pico. The receiver's SBUS has a baudrate of 100000, but I have yet to be able to receive data from it with Pi Pico. Is RP2040 able to communicate at 100000 baud at its default operating frequency?

[robert-hh]

Yes. I have tested UART at 4_000_000 baud for data loss. And it worked fine. Just take care that rxbuf is larger than the longest message which you expect.

[swiftimundo]

Good to know. My rxbuf=250, which I believe should be larger than my longest message.

[robert-hh]

rxbuf=256 is the default.

[swiftimundo]

ahh ok, would an low rxbuf prevent me from receiving anything? It seems like I may not be receiving any bytes.

[robert-hh]

No. You can set it to any value >= 32. You should receive data, if it's properly connected with GND and RX.

[swiftimundo]

yea I'm pretty sure it is... I think my next step is to get my scope out and see that it's actually transmitting and my logic level shifter is working..
Thanks

[GitHubsSilverBullet]

I'm trying to use an RC receiver's SBUS with Pi Pico. The receiver's SBUS has a baudrate of 100000, but I have yet to be able to receive data from it with Pi Pico. Is RP2040 able to communicate at 100000 baud at its default operating frequency?

The SBUS protocol is not a valid protocol for a standard UART.
I'd be very surprised if you could receive any sensible data using a standard UART. Because that would require a startbit (low), 5…8 databits, maybe a parity bit and definitely a stop bit(high).
SBUS could send you up to 16 bits.

[swiftimundo]

Thanks for the info, sorry for not responding sooner.
Here are my UART init lines

sbus = UART(1, 100000)
sbus.init(bits=8, parity=0, stop=2, invert=UART.INV_TX | UART.INV_RX)

Since micropython now supports inverting on UART, is it necessary to configure the GPIO like you did? I should note I'm still not able to read any data, though I have confirmed with my scope that data is being passed.

[robert-hh]

You have to repeat the baudrate in the init() call, otherwise it will be set to the default of 115200. You can as well use all init arguments in the instantiation call.

[GitHubsSilverBullet]

Since micropython now supports inverting on UART,

Ahh, didn't know that. Something new to learn every day.
And no, that somewhat messy setup won't be necessary anymore.

[robert-hh]

I recalled that wrong for the rp2 port. If baudrate is not set, the previously set value rules.

[swiftimundo]

FINALLY got output! I had switched to UART1 because UART0 wasnt working for me... but I just switched back and got a flood of data! Now to decode.
Thank you both for your help, not sure which to mark as the answer because I got a piece of the puzzle from each response.

Here's what I ended up with.

sbus = UART(0, 100000, rx=17)
sbus.init(baudrate=100000, rx=17, bits=8, parity=0, stop=2, invert=UART.INV_RX)