ADC1 operation affecting GPIO27 - chip issue?

yugguy
Posts: 3
Joined: Sun Nov 26, 2017 12:47 am

ADC1 operation affecting GPIO27 - chip issue?

Postby yugguy » Sun Nov 26, 2017 12:54 am

I've got GPIO27 configured as a digital input (with both an external pull-up and internal pull-up enabled), but when I perform ADC1 conversion operations, IO27 glitches 'low' for about 6us. With a 10K pull-up, the glitch is about 1V (drops to ~2.3V). With a weaker pull-up, the glitch is low enough to hit a logic low threshold and I get a spurious interrupt.

No other pins are affected. Has anyone observed interaction between ADC and GPIO27? It feels like a chip bug. U can use a strong pull-up as a work-around, but would like to understand what's going on.

Darmann
Posts: 2
Joined: Sun Mar 04, 2018 12:40 pm

Re: ADC1 operation affecting GPIO27 - chip issue?

Postby Darmann » Sun Mar 04, 2018 1:09 pm

I found the same adc1 side effect on gpi39 and gpi36. I think there is a relationship between adc1 operation and the hall effect sensor.
In my program I do adc1_ch0 read (20ms), and every time I will get gpio interrupt on gpi39 and gpi36. My solution: move gpio interrupts away from gpi39 and gpi36.
In normal polling mode, hopefully there will be no side effect.
Attachments
2018-03-04 13_57_58-PicoScope 6.png
GPI36 ... side effect
2018-03-04 13_57_58-PicoScope 6.png (20.46 KiB) Viewed 6631 times
2018-03-04 14_01_44-PicoScope 6.png
GPI35 ... no side effect
2018-03-04 14_01_44-PicoScope 6.png (12.55 KiB) Viewed 6631 times
2018-03-04 14_00_35-PicoScope 6.png
GPI39 ... side effect
2018-03-04 14_00_35-PicoScope 6.png (42.83 KiB) Viewed 6631 times

WiFive
Posts: 3529
Joined: Tue Dec 01, 2015 7:35 am

Re: ADC1 operation affecting GPIO27 - chip issue?

Postby WiFive » Mon Mar 05, 2018 1:44 am

36&39 is a known issue, check eco workaround PDF. Not sure if anyone else has reported 27.

ESP_Sprite
Posts: 9709
Joined: Thu Nov 26, 2015 4:08 am

Re: ADC1 operation affecting GPIO27 - chip issue?

Postby ESP_Sprite » Mon Mar 05, 2018 8:44 am

Wifive: Yep, conformed by the hardware guys, but GPIO27 is also new to them. If someone runs into this, please post the source code so we can double-check this.

kuhatovuk
Posts: 21
Joined: Thu Aug 01, 2019 8:46 pm

Re: ADC1 operation affecting GPIO27 - chip issue?

Postby kuhatovuk » Sat Mar 28, 2020 5:25 pm

Hello, same thing with ADC1_CHANNEL_2 and IO25 internally pulled up. ADC reads trigger its LOW edge interrupt.

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