cores/psoc6: docs: Implement read resolution API and document changes.

Signed-off-by: Ramya Subramanyam <[email protected]>

Author: ramya-subramanyam

cores/psoc6/Arduino.h

@@ -45,6 +45,7 @@ extern bool gpio_initialized[];
 #define digitalPinToInterrupt(p) ((p) < GPIO_PIN_COUNT ? (p) : -1)
 #define PWM_FREQUENCY_HZ    1000  // 1 kHz
 void analogWriteResolution(int res);
+void analogReadResolution(int res);
 
 #undef LITTLE_ENDIAN
 

cores/psoc6/analog_io.c

@@ -33,6 +33,7 @@ static cyhal_adc_t adc_obj = {0};
 static cyhal_adc_vref_t desiredVRef = CYHAL_ADC_REF_VDDA;
 static bool adc_initialized = false;
 static adc_channel_t adc_channel[ADC_HOWMANY] = {0};
+static int desiredReadResolution = ADC_RESOLUTION;
 static float desiredWriteResolution = PWM_RESOLUTION_8_BIT;
 static pwm_t pwm[PWM_HOWMANY] = {0};
 
@@ -79,6 +80,24 @@ static cy_rslt_t initialize_adc_channel(pin_size_t pinNumber, uint8_t adc_index)
     return status;
 }
 
+void analogReadResolution(int res) {
+    if (res < 1) {
+        desiredReadResolution = 1; // Minimum resolution
+    } else {
+        desiredReadResolution = res;
+    }
+}
+
+static inline uint32_t  map_adc_value(uint32_t adc_value) {
+    uint8_t adc_res = ADC_RESOLUTION - 1; // 11-bit ADC resolution
+    if (desiredReadResolution == adc_res) {
+        return adc_value; // already in desired resolution
+    } else if (desiredReadResolution < adc_res) {
+        return adc_value >> (adc_res - desiredReadResolution); // reduce resolution
+    }
+    return adc_value << (desiredReadResolution - adc_res); // increase resolution
+}
+
 int analogRead(pin_size_t pinNumber) {
     int adc_value = 0;
     uint8_t adc_index = 0;
@@ -101,6 +120,12 @@ int analogRead(pin_size_t pinNumber) {
     if (adc_index < ADC_HOWMANY) {
         adc_value = cyhal_adc_read(&adc_channel[adc_index].chan_obj);
     }
+
+    if (adc_value <= 0) {
+        adc_value = 0; // Ensure non-negative value
+    } else {
+        adc_value = map_adc_value((uint32_t)adc_value);
+    }
     return adc_value;
 }
 

docs/arduino-deviations.rst

@@ -28,17 +28,15 @@ Analog IO
 
 Once a pin is configured and used as an ADC input, it may no longer be available for use with any other peripherals (e.g., PWM, I2C, SPI, GPIO, etc.).
 
-The `PSOC6-for-Arduino` core does not support the following Arduino APIs:
-
-
 .. code-block:: cpp
 
     void analogReadResolution(uint8_t bits)
 
-This API is **not implemented** because the resolution is hardware-defined and fixed at 11 bits and the resolution cannot be dynamically reconfigured by firmware.
-
-For applications requiring lower effective resolutions (e.g., 8-bit or 10-bit), users can manually scale the 11-bit ADC result in their application code by discarding the least significant bits (LSBs).
+The default ADC_RESOLUTION is fixed at 11 bits (range: 0–2047) due to hardware limitations.
+Depending on the bits parameter, the function modifies the resolution of the ADC value:
 
+- If bits < ADC_RESOLUTION: The resolution of the ADC value is reduced by truncating the least significant bits (LSBs).
+- If bits > ADC_RESOLUTION: The resolution of the ADC value is increased by appending zeros to the least significant bits (LSBs).
 
 .. code-block:: cpp