UART max Baud rate

Knochi · December 12, 2024, 5:28pm

Hi,
recently I bought a Bambulab A1 Mini and I wonder if I could Sniff the Bambu Bus.
It’s an UART over RS485, so if I take care of the RS485 and level shifting i could feed that into the BP. But is it able to handle the 1228800bps?

So the datasheet of the RP2040 states

supports the a maximum baud rates of 921600 bps in UART mode

The RP2350 is not that clear. I had a brief look into all this dividers and init functions to calculate the clocks from a given baud rate. It seems possible, but I can’t say for sure.

Anyway I have only the RP5 (nonXL), is it possible to do with PIO or so?

ian · December 12, 2024, 5:36pm

Hi knochi -

Currently there are no settings higher than 900k-ish because that is what the RP2040 datasheet lists as the limit, but I just checked and people have been able to get it up to 7.x MBPS.

The problem is the dividers get small and the resolution less precise. I’m at the end of my day today, but I will do some testing and increase the max speed first thing tomorrow and report back how close we can get to 1228800bps.

I’d love to know if you can sniff the Bambu bus with the Bus Pirate.

ian · December 12, 2024, 5:48pm

Yeah, that’s out of bounds.

But it does report the actual speed.

Increased it to the theoretical max.

It’s close, but I don’t know if it is close enough at these speeds.

If this isn’t close enough, maybe on of the PIO UART programs can get closer.

Pushed this update, an autobuild should appear in a moment.