Implement analogReadResolution

Co-Authored-by: Kurt Eckhardt <kurte@rockisland.com>
Signed-off-by: TOKITA Hiroshi <tokita.hiroshi@gmail.com>

Author: KurtE

cores/arduino/Arduino.h

@@ -104,6 +104,9 @@ enum analogPins {
 	DT_FOREACH_PROP_ELEM(DT_PATH(zephyr_user), adc_pin_gpios, AN_ENUMS)
 };
 
+// We provide analogReadResolution APIs
+void analogReadResolution(int bits);
+
 #endif
 
 #ifdef CONFIG_DAC

cores/arduino/zephyrCommon.cpp

@@ -504,9 +504,20 @@ void analogReference(uint8_t mode) {
 	}
 }
 
+// Note: We can not update the arduino_adc structure as it is read only...
+static int read_resolution = 10;
+
+void analogReadResolution(int bits) {
+	read_resolution = bits;
+}
+
+int analogReadResolution() {
+	return read_resolution;
+}
+
 int analogRead(pin_size_t pinNumber) {
 	int err;
-	int16_t buf;
+	uint16_t buf;
 	struct adc_sequence seq = {.buffer = &buf, .buffer_size = sizeof(buf)};
 	size_t idx = analog_pin_index(pinNumber);
 
@@ -536,7 +547,17 @@ int analogRead(pin_size_t pinNumber) {
 		return err;
 	}
 
-	return buf;
+	/*
+	 * If necessary map the return value to the
+	 * number of bits the user has asked for
+	 */
+	if (read_resolution == seq.resolution) {
+		return buf;
+	}
+	if (read_resolution < seq.resolution) {
+		return buf >> (seq.resolution - read_resolution);
+	}
+	return buf << (read_resolution - seq.resolution);
 }
 
 #endif