mbed OS serial port hang.

[maxv]

Hi,

I've got a nice, well-documented bug here: github.com/.../25

The short of it: Adding a single printf() statement to this mbed OS example causes my nRF51-DK board to hang eventually, if I don't connect to the exposed /dev/ttyACM0 port using minicom or similar terminal program.

I think the serial port code for the Nordic chips in the HAL has issues w/non hardware-flow controlled configurations.

I suppose I can remove all printf() calls in production, but this is really not ideal even for early prototyping.

Max

[maxv]

Actually, I just realized also that this is potentially the reason why creating a Peripheral device and hooking it up to a USB power bank instead of to a PC always caused it hang within a few seconds.

[Dimitri]

Hi Max,

I am also experiencing the same issue with mbed OS on a nRF52-DK V1.1.0. I hope Nordic can quickly fix this as I am aggressively prototyping with the nRF52. It's good to know I'm not the only one experiencing this!

Dimitri

[maxv]

Yeah I had problems with this on an nRF52-DK as well, when using only the pure Nordic nRF5 SDK. I've had some serious upset moments with the serial port over the past 6 months.

[maxv]

This has finally been resolved, meaning that mbed OS is actually useful to people using the Nordic serial port w/o hardware flow control.

Issues: github.com/.../25

The short answer: Create an mbed_app.json file in your app folder, and add the following to it:

"NRF51_DK": { "target.uart_hwfc": 0 }

or in your case, probably:

"NRF52_DK": { "target.uart_hwfc": 0 }

[Dimitri]

Great! This works now! Thank you Max!