WP7700 UART1 on RPI header


I am having some issues with UART 1 on my WP7700 with the Mangoh Red.

Trace 1 is pin 10 of the rpi header.
Trace 3 is pin 12 of the Iot header. (connected directly to WP)

I am trying to use the UART to talk to an external micro, sometimes it works, but a lot of the time I see this mess.
I have a bunch of Mangohs here, it is happening on all of them so far.
Has anyone come across this before?
If looks like the gpio for the rx pin (labelled as tx?) (gpio5) is being driven, and the FXMA108 is unable to distinguish the input from the output anymore, and attempts to drive the TX line from the other micro.


Firmware Version: SWI9X06Y_02.13.02.00 7cfe8a jenkins 2017/12/22 05:21:50


check configuration for your uart:

Are you driving the UART port through linux or AT commands? Also, read through other posts on this topic.


I am driving the UART through Linux.
My previous post mentions the config of the UART:


Part of the problem was me not installing the mangOH services. Updated screen caps below.
It seems that the ripple on either the 3v3 or 1v8 rail is causing the FXMA108 to play up.

I have read through every post on this topic that I could find, but I couldn’t see anything that applied to this. It occurs on every device we have here, so you should be able to reproduce it at your end.
Trace 1 is pin 10 on the RPi header. Trace 2 is pin 8 on the RPi header.