Issue with Serial0.write(0)

I'm having issues with the Serial0.write() function when trying to write 0x00 to the serial port.

Example - the following code produces NOTHING on the serial port.

uint8_t val;
while (1)
{
val = 0;
Serial0.write(val);
val = 1;
Serial0.write(val);
val = 2;
Serial0.write(val);
}

But if you change val = 0 to val = 3 then it works as expected.

I came across this issue while trying to use the ModbusMaster library. I'm missing bytes from the Modbus packets because any 0x00 bytes are getting dropped.

Does anyone have a fix for this?

 

It is a known issue and no update on it yet unfortunately: http://www.udoo.org/forum/threads/solved-accessing-dev-ttymcc-kernel-panics-linux.4375/#post-19613

 

Thanks waltervl.

Udoo team: Is there an estimated timeframe for when this will be fixed? I need a working serial port for the product I am working on. I have to decide whether I can wait for the fix, or try a different platform.

 

Is this something I can potentially fix myself?

On my windows development machine I have a folder AppData\Local\Arduino15\packages\UDOO\hardware\solox\1.6.7\variants\udooneo. Inside this folder are a bunch of source files - some of which look like they are related to the UART. If I spend time digging through this am I likely to find the source code that is getting called when I invoke Serial0.write() ?

 

Yes you could try to fix it yourself in the sources in that folder. That would be highly appreciated!

Be aware that there is also a MQX part in it that is proprietary software of NXP. So only compiled versions of that part.

 

Knick,

Did you succeed to fix it?

 

This is exactly the same problem I have using Modbus RTU. Unfortunately I designed a board to host a Udoo NEO and now I discovered this incredible issue.

 

I have the same problem.
Any fix or update?

 

Not that I know of.

 

Got to workaround by putting Serial0.flush() after writing a byte.

while (true){
Serial0.write(0);
Serial0.flush();
}

 

Nice work! At least a work around found. Do you have to flush after every write() ?

 

No, you will need to flush just when sending a zero.
I think the problem can be from somewhere in the serial buffer which assume that data is always a string.

 

It would be better if you cast to byte too.
Serial0.write((byte)0x00)
even if it doesn't solve the problem but flushing does.