Uart not always transmitting

I’m connecting my imp to a 3.3v Arduino through the UART

Transmitting from Arduino -> Imp works every time

Transmitting from Imp -> Arduino only works sometimes, cycling the power on both can get this to work, but it seems random.

uart setup:
hardware.uart12.configure(115200, 8, PARITY_NONE, 1, NO_CTSRTS, readserial);

uart send:

The server will report the flags, which will be either 2 or 66, which looks like ‘WRITE_DONE’ or ‘WRITE_DONE + LINE_IDLE’

I have tried this on 2 different imp boards, although only 1 Arduino so far.

I think this is an issue with the transmit, as I’ve connected the serial monitor to the imp uart output and seen nothing come through.

Any help appreciated, thanks!

That was it, pin 1 wasn’t connecting.

I added a small blob of solder to the pin on the imp and everything it working reliably now.


Is this an imp001 in a socket? There was an issue with making bad connections on pin1 (which is the transmit pin for uart12). See this thread.


Hi Peter

Yes it is an imp001, and yes I’m using uart12. A physical issue like that would certainly explain why the problem is intermittent.

I’ll check it out later and see if that is the issue.



btw if you have an imp with bad pin 1, then contact us and we can replace it for you.