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.
ADC1 operation affecting GPIO27 - chip issue?
Re: ADC1 operation affecting GPIO27 - chip issue?
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.
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
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- GPI36 ... side effect
- 2018-03-04 13_57_58-PicoScope 6.png (20.46 KiB) Viewed 6708 times
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- GPI35 ... no side effect
- 2018-03-04 14_01_44-PicoScope 6.png (12.55 KiB) Viewed 6708 times
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- GPI39 ... side effect
- 2018-03-04 14_00_35-PicoScope 6.png (42.83 KiB) Viewed 6708 times
Re: ADC1 operation affecting GPIO27 - chip issue?
36&39 is a known issue, check eco workaround PDF. Not sure if anyone else has reported 27.
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Re: ADC1 operation affecting GPIO27 - chip issue?
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.
Re: ADC1 operation affecting GPIO27 - chip issue?
Hello, same thing with ADC1_CHANNEL_2 and IO25 internally pulled up. ADC reads trigger its LOW edge interrupt.
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