Correctly scale analog reading per issue #4794

PaintYourDragon · web-flow · commit e9b9f0b13fac · 2022-05-24T08:42:00.000-07:00
diff --git a/ports/stm/common-hal/analogio/AnalogIn.c b/ports/stm/common-hal/analogio/AnalogIn.c
@@ -204,8 +204,8 @@ uint16_t common_hal_analogio_analogin_get_value(analogio_analogin_obj_t *self) {
     uint16_t value = (uint16_t)HAL_ADC_GetValue(&AdcHandle);
     HAL_ADC_Stop(&AdcHandle);
 
-    // // Shift the value to be 16 bit.
-    return value << 4;
+    // Stretch 12-bit ADC reading to 16-bit range
+    return (value << 4) | (value >> 8);
 }
 
 float common_hal_analogio_analogin_get_reference_voltage(analogio_analogin_obj_t *self) {

Original file line number	Diff line number	Diff line change
`@@ -204,8 +204,8 @@ uint16_t common_hal_analogio_analogin_get_value(analogio_analogin_obj_t *self) {`
`204`	`204`	`uint16_t value = (uint16_t)HAL_ADC_GetValue(&AdcHandle);`
`205`	`205`	`HAL_ADC_Stop(&AdcHandle);`
`206`	`206`
`207`		`- // // Shift the value to be 16 bit.`
`208`		`- return value << 4;`
	`207`	`+ // Stretch 12-bit ADC reading to 16-bit range`
	`208`	`+ return (value << 4) \| (value >> 8);`
`209`	`209`	`}`
`210`	`210`
`211`	`211`	`float common_hal_analogio_analogin_get_reference_voltage(analogio_analogin_obj_t *self) {`