nRF52832 UART communication data format (about start bit)

[Yclee]

Hello,

I am testing nRF52 UART with DSP.

While transmit data in nRF52 (ADC results) 

(example link: https://github.com/NordicPlayground/nRF52-ADC-examples)

I can show the wave like below.

But I have one question. The serial communication (include UART) has start bit in data format.

And I found the start bit is low(0). But when I see the output wave, the bit was not changed to low(0).

So I think that's why the DSP can't receive the nRF52 data with UART communication(since there is no start bit detected).

Is there a method that I can change the start bit setting? or other method?

Thank you for reading my questions.

Best regards,

Yclee.

[awneil]

Doesn't your scope have a proper screenshot facility - rather that taking a photo of the screen?

From that trace, it looks like nothing at all is happening - it's not just the Start bit that's missing?

Are you sure that you've correctly configured the correct pins?

Yclee said:

the DSP

What DSP ?

[Yclee]

Maybe it really nothing happens.

The used DSP is TMS320F28335 module.

However, I wonder the PC can receive message but the signal is like that.

And I will screen the signal, and upload later.

I was check the pin configuration of the DSP module.

Thank you for reply.

[awneil]

Yclee said:

The used DSP is TMS320F28335 module

This is actually irrelevant - the UART neither knows nor cares what it's connected to.

In fact, for testing, you should take the DSP out of the equation - it's just an extra source of possible problems and confusion.

Instead, connect the UART to a PC (via a suitable adaptor), and test using a terminal app

If it doesn't work with a PC, it won't work with anything else.

Yclee said:

I wonder the PC can receive message but the signal is like that.

Of course not:  it it's not a valid UART signal, then no UART - whether in a DSP or PC or anything else - is going to make any sense of it.

Yclee said:

I was check the pin configuration of the DSP module.

If you're looking at what's transmitted by the nRF52, then you need to be looking at the nRF52 pin configuration

[Yclee]

Thank you and sorry for late answer verifying.

I understand that this is not effective signal output, and first I will check the signal or data.

I think I need more study & test about UART signal.

Thank you.

Best Regards,

Yclee