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Workaround for ESP32-C6 one-shot ADC #876

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Merged
jessebraham merged 2 commits into from
Oct 26, 2023
Merged

Workaround for ESP32-C6 one-shot ADC #876

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Workaround for ESP32-C6 one-shot ADC
bjoernQ Oct 26, 2023
981b1e1
CHANGELOG.md entry
bjoernQ Oct 26, 2023
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
- Fixed a race condition causing SpiDma to stop working unexpectedly (#869)
- Fixed async uart serial, and updated the embassy_serial examples (#871).
- Fix ESP32-S3 direct-boot (#873)
- Fix ESP32-C6 ADC (#876)

### Removed

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13 changes: 13 additions & 0 deletions esp-hal-common/src/analog/adc/riscv.rs
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Expand Up @@ -646,6 +646,19 @@ where
let attenuation = self.attenuations[channel as usize].unwrap() as u8;
ADCI::config_onetime_sample(channel, attenuation);
ADCI::start_onetime_sample();

// see https://github.com/espressif/esp-idf/blob/b4268c874a4cf8fcf7c0c4153cffb76ad2ddda4e/components/hal/adc_oneshot_hal.c#L105-L107
// the delay might be a bit generous but longer delay seem to not cause problems
#[cfg(esp32c6)]
{
extern "C" {
fn ets_delay_us(us: u32);
}
unsafe {
ets_delay_us(40);
}
ADCI::start_onetime_sample();
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@bugadani bugadani Oct 26, 2023 •
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This isn't the same sequence as the linked C code: that is a bit_clear(); wait; bit_set() sequence, while this looks like two bit sets. It's interesting how the workaround still seems to work, I wonder what actually needs the delay.

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@bjoernQ bjoernQ Oct 26, 2023

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Yes, it's not the same thing - but works

}
}

// Wait for ADC to finish conversion
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