From 6bb17bb1794a5348799a1cdfae70d3b93795abbc Mon Sep 17 00:00:00 2001
From: anecdata <16617689+anecdata@users.noreply.github.com>
Date: Thu, 17 Oct 2019 00:12:35 -0500
Subject: [PATCH] Add basic ADC calibration.

---
 arduino/cores/esp32/wiring_analog.c | 22 +++++++++++++++++++---
 arduino/cores/esp32/wiring_analog.h |  2 +-
 main/CommandHandler.cpp             |  4 +++-
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/arduino/cores/esp32/wiring_analog.c b/arduino/cores/esp32/wiring_analog.c
index e72650d..9b80a0c 100644
--- a/arduino/cores/esp32/wiring_analog.c
+++ b/arduino/cores/esp32/wiring_analog.c
@@ -19,6 +19,7 @@
 
 #include <driver/ledc.h>
 #include <driver/adc.h>
+#include <esp_adc_cal.h>
 #include <soc/adc_channel.h>
 
 #include "wiring_analog.h"
@@ -46,33 +47,48 @@ void analogWrite(uint32_t pin, uint32_t value)
   ledc_channel_config(&ledc_conf);
 }
 
-int analogRead(uint32_t pin)
+int analogRead(uint32_t pin, uint32_t atten)
 {
-  int channel;
+  #define DEFAULT_VREF 1100
+  static esp_adc_cal_characteristics_t *adc_chars;
+  adc_channel_t channel;
+
   switch(pin)
   {
     case ADC1_CHANNEL_0_GPIO_NUM:
       channel = ADC1_GPIO36_CHANNEL;
+      break;
     case ADC1_CHANNEL_1_GPIO_NUM:
       channel = ADC1_GPIO37_CHANNEL;
+      break;
     case ADC1_CHANNEL_2_GPIO_NUM:
       channel = ADC1_GPIO38_CHANNEL;
+      break;
     case ADC1_CHANNEL_3_GPIO_NUM:
       channel = ADC1_GPIO39_CHANNEL;
+      break;
     case ADC1_CHANNEL_4_GPIO_NUM:
       channel = ADC1_GPIO32_CHANNEL;
+      break;
     case ADC1_CHANNEL_5_GPIO_NUM:
       channel = ADC1_GPIO33_CHANNEL;
+      break;
     case ADC1_CHANNEL_6_GPIO_NUM:
       channel = ADC1_GPIO34_CHANNEL;
+      break;
     case ADC1_CHANNEL_7_GPIO_NUM:
       channel = ADC1_GPIO35_CHANNEL;
+      break;
     default:
       return -1;
   }
 
   adc1_config_width(ADC_WIDTH_BIT_12);
-  adc1_config_channel_atten(channel, ADC_ATTEN_DB_11);
+  adc1_config_channel_atten(channel, atten);
+
+  adc_chars = calloc(1, sizeof(esp_adc_cal_characteristics_t));
+  esp_adc_cal_characterize(ADC_UNIT_1, atten, ADC_WIDTH_BIT_12, DEFAULT_VREF, adc_chars);
+
   int val = adc1_get_raw(channel);
   return val;
 }
diff --git a/arduino/cores/esp32/wiring_analog.h b/arduino/cores/esp32/wiring_analog.h
index 0902ac0..2bc480d 100644
--- a/arduino/cores/esp32/wiring_analog.h
+++ b/arduino/cores/esp32/wiring_analog.h
@@ -28,7 +28,7 @@ extern "C" {
 
 extern void analogWrite(uint32_t pin, uint32_t value);
 
-extern int analogRead(uint32_t pin);
+extern int analogRead(uint32_t pin, uint32_t atten);
 
 #ifdef __cplusplus
 }
diff --git a/main/CommandHandler.cpp b/main/CommandHandler.cpp
index db81052..bca87bb 100644
--- a/main/CommandHandler.cpp
+++ b/main/CommandHandler.cpp
@@ -1010,11 +1010,13 @@ int setDigitalRead(const uint8_t command[], uint8_t response[])
 int setAnalogRead(const uint8_t command[], uint8_t response[])
 {
   uint8_t pin = command[4];
+  uint8_t atten = command[6];
 
-  int value = digitalRead(pin);
+  int value = analogRead(pin, atten);
 
   response[2] = 1; // number of parameters
   response[3] = sizeof(value); // parameter 1 length
+
   memcpy(&response[4], &value, sizeof(value));
 
   return 5 + sizeof(value);