rp2/machine_adc: Only initialise the ADC periph if not already enabled.

dpgeorge · dpgeorge · commit 7f7b4f2bc68a · 2021-02-04T10:55:43.000+11:00
Otherwise it resets the ADC peripheral each time a new ADC object is constructed, which can reset other state that has already been set up. See issue micropython#6833. Signed-off-by: Damien George <damien@micropython.org>
diff --git a/ports/rp2/machine_adc.c b/ports/rp2/machine_adc.c
@@ -78,7 +78,10 @@ STATIC mp_obj_t machine_adc_make_new(const mp_obj_type_t *type, size_t n_args, s
         }
     }
 
-    adc_init();
+    // Initialise the ADC peripheral if it's not already running.
+    if (!(adc_hw->cs & ADC_CS_EN_BITS)) {
+        adc_init();
+    }
 
     if (ADC_IS_VALID_GPIO(channel)) {
         // Configure the GPIO pin in ADC mode.

Original file line number	Diff line number	Diff line change
`@@ -78,7 +78,10 @@ STATIC mp_obj_t machine_adc_make_new(const mp_obj_type_t *type, size_t n_args, s`
`78`	`78`	`}`
`79`	`79`	`}`
`80`	`80`
`81`		`- adc_init();`
	`81`	`+ // Initialise the ADC peripheral if it's not already running.`
	`82`	`+ if (!(adc_hw->cs & ADC_CS_EN_BITS)) {`
	`83`	`+ adc_init();`
	`84`	`+ }`
`82`	`85`
`83`	`86`	`if (ADC_IS_VALID_GPIO(channel)) {`
`84`	`87`	`// Configure the GPIO pin in ADC mode.`