Workaround for ESP32-C6 one-shot ADC (#876)

* Workaround for ESP32-C6 one-shot ADC * CHANGELOG.md entry
esp-rs · Oct 26, 2023 · 663cbd9 · 663cbd9
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -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
 

diff --git a/esp-hal-common/src/analog/adc/riscv.rs b/esp-hal-common/src/analog/adc/riscv.rs
@@ -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();
+            }
         }
 
         // Wait for ADC to finish conversion