rp2/machine_adc: Refactor channel/pin validation code.

This patch ensures that integer channel numbers passed to the ADC
constructor (including temperature sensor) are interpreted as raw
channel numbers, and not cause any GPIO pins to be initialized.

Signed-off-by: iabdalkader <i.abdalkader@gmail.com>

1 files changed, 17 insertions, 15 deletions

diff --git a/ports/rp2/machine_adc.c b/ports/rp2/machine_adc.c
index 80c4d0533..3a7a71a74 100644
--- a/ports/rp2/machine_adc.c
+++ b/ports/rp2/machine_adc.c
@@ -69,21 +69,21 @@ STATIC mp_obj_t mp_machine_adc_make_new(const mp_obj_type_t *type, size_t n_args
 
     mp_obj_t source = all_args[0];
 
-    uint32_t channel;
+    uint32_t channel = -1;
     bool is_ext = false;
     const machine_pin_obj_t *pin = NULL;
 
     if (mp_obj_is_int(source)) {
         // Get and validate channel number.
         channel = mp_obj_get_int(source);
-        if (!((channel >= 0 && channel <= ADC_CHANNEL_TEMPSENSOR) || ADC_IS_VALID_GPIO(channel))) {
+        if (ADC_IS_VALID_GPIO(channel)) {
+            channel = ADC_CHANNEL_FROM_GPIO(channel);
+        } else if (!(channel >= 0 && channel <= ADC_CHANNEL_TEMPSENSOR)) {
             mp_raise_ValueError(MP_ERROR_TEXT("invalid channel"));
         }
-
     } else {
         // Get GPIO and check it has ADC capabilities.
         pin = machine_pin_find(source);
-        channel = pin->id;
         bool valid_adc_pin = false;
         #if MICROPY_HW_ADC_EXT_COUNT
         is_ext = pin->is_ext;
@@ -92,7 +92,7 @@ STATIC mp_obj_t mp_machine_adc_make_new(const mp_obj_type_t *type, size_t n_args
         } else
         #endif
         {
-            valid_adc_pin = ADC_IS_VALID_GPIO(channel);
+            valid_adc_pin = ADC_IS_VALID_GPIO(pin->id);
         }
         if (!valid_adc_pin) {
             mp_raise_ValueError(MP_ERROR_TEXT("Pin doesn't have ADC capabilities"));
@@ -104,16 +104,18 @@ STATIC mp_obj_t mp_machine_adc_make_new(const mp_obj_type_t *type, size_t n_args
         adc_init();
     }
 
-    if (is_ext) {
-        #if MICROPY_HW_ADC_EXT_COUNT
-        // Note external pins are mutable.
-        machine_pin_ext_config((machine_pin_obj_t *)pin, MACHINE_PIN_MODE_ANALOG, 0);
-        channel = machine_pin_ext_to_adc_channel(pin);
-        #endif
-    } else if (ADC_IS_VALID_GPIO(channel)) {
-        // Configure the GPIO pin in ADC mode.
-        adc_gpio_init(channel);
-        channel = ADC_CHANNEL_FROM_GPIO(channel);
+    if (pin) {
+        if (is_ext) {
+            #if MICROPY_HW_ADC_EXT_COUNT
+            // Note external pins are mutable.
+            machine_pin_ext_config((machine_pin_obj_t *)pin, MACHINE_PIN_MODE_ANALOG, 0);
+            channel = machine_pin_ext_to_adc_channel(pin);
+            #endif
+        } else {
+            // Configure the GPIO pin in ADC mode.
+            adc_gpio_init(pin->id);
+            channel = ADC_CHANNEL_FROM_GPIO(pin->id);
+        }
     } else if (channel == ADC_CHANNEL_TEMPSENSOR) {
         // Enable temperature sensor.
         adc_set_temp_sensor_enabled(1);