topic Re: S08DZ60 A/D fluctuating in 8-bit Microcontrollers

S08DZ60 A/D fluctuating

jiaqihe — Thu, 25 Apr 2019 17:35:17 GMT

I am using the S08DZ60 for graduation design, but I have a problem. The A/D sample value is always fluctuating, the amplitude is about 10, and the voltage of the oscilloscope observation sampling point is stable. I tried all the methods I could think of, but it didn't work. I hope I can get any help, thank you very much. I will be very grateful if someone can help me. I really have no idea.

Re: S08DZ60 A/D fluctuating

tonyp — Fri, 26 Apr 2019 10:23:21 GMT

Is that 10 out of 1023 (10 bit mode)?

Re: S08DZ60 A/D fluctuating

jiaqihe — Sat, 27 Apr 2019 19:12:28 GMT

12 bit mode, and A/D sampling reference voltage is also stable. I have changed another MCU, but it didn't work.

Re: S08DZ60 A/D fluctuating

vicentegomez — Mon, 29 Apr 2019 20:11:24 GMT

Are you using high-speed mode?

We recommend to use low power configuration (ADLPC).

Regards

Re: S08DZ60 A/D fluctuating

tonyp — Tue, 30 Apr 2019 06:16:04 GMT

You could average multiple readings (say, 4) per sample to minimize the fluctuation.

And use the lowest clock for the A/D.

Re: S08DZ60 A/D fluctuating

jiaqihe — Sat, 04 May 2019 15:19:13 GMT

I confirmed that I am using low power mode. And it didn't work.

Re: S08DZ60 A/D fluctuating

jiaqihe — Sat, 04 May 2019 15:26:14 GMT

I have averaged multiple readings, but it works not well. Then I change the A/D clock to 1MHz, but it doesn't work. Is the problem probably in the program?

Re: S08DZ60 A/D fluctuating

vicentegomez — Mon, 06 May 2019 16:21:22 GMT

I just read you have an error of 10 of 4096 (12 bit) ?

Can you check if you have other modules enable at the same time that you are making the measurements? or if you have noise on the system, maybe you have a signal input in other pin that is affecting your ADC measurement

Regards

Re: S08DZ60 A/D fluctuating

jiaqihe — Fri, 10 May 2019 05:03:17 GMT

Thank you a lot. The problem is solved, my 5V reference voltage design is problematic, causing interference to A/D sampling. Redesigned and solved.

Re: S08DZ60 A/D fluctuating

vicentegomez — Mon, 13 May 2019 13:00:09 GMT

Excellent that you found the problem, let me know if you have more questions