Slow serial

Could the imp be given access to slower baud rates, some commercial devices can only accept slower rates for reasons such as line length (the slower you go, the further you can go)

For example the project I have in mind needs 9600

The imp does 9600 no problem. Are you having issues?

The floor is either 460 or 920bps, depending on the UART. See

I can confirm 2400 works. I have had an application like that running since late 2012 talking to Arduino.

Okay, that’s great, I got confused because of another forum topic

It’s sad that my first 300 & 1200/75 baud modem wouldn’t be fully supported by an imp, but I guess technology moves on!

Is 460 baud a hardware limitation or “just” software?
I’m asking as a lot of electric meters use 300 baud as base communication acording EN62056-21 / IEC1107 specifications.
I think the imp is the ideal communication device for such meters.
It would no be efficient to use another microcontroller to read the data, transmit them over a higher speed to the imp …

It’s a hardware limitation. Which I was a bit surprised by too, to be honest :frowning:


Have someone experience with SPI to UART with MAX3100 or any other converter? Ok, it’s a littlebit expensiv but for the oldstyle guys who need slower baud rates it can be an option :slight_smile:

sorry double post with crappy IE …

@abeda Technically, we could slow the internal busses down to get the right baudrate, but that would be losing performance. Doesn’t seem to be ideal as a trade-off!

There are several I2C/SPI connected UARTs these days. NXP have one here:,112&cur=USD

…for 300 baud, you might be fine just hanging it off I2C. You could also likely drive its clock input pin from an imp PWM so you wouldn’t need a crystal?