add ADC support

cores/arduino/Arduino.h

@@ -52,4 +52,7 @@
 void analogReadResolution(int bits);
 void analogWriteResolution(int bits);
 
+#define ADC_CH_REF 0x40 // Vref
+#define ADC_CH_CAL 0x41 // Vcal
+
 #endif

cores/arduino/wiring_digital.cpp

@@ -112,3 +112,149 @@ PinStatus digitalRead(pin_size_t pin)
 
     return (port->INDR & (1 << p)) != 0 ? HIGH : LOW;
 }
+int analogRead(uint8_t pin)
+{
+    /*
+        GPIO -> ADC Channel
+        PA2 -> A0
+        PA1 -> A1
+        PC4 -> A2
+        PD2 -> A3
+        PD3 -> A4
+        PD5 -> A5
+        PD6 -> A6
+        PD4 -> A7
+        ADC_CH_REF -> A8
+        ADC_CH_CAL -> A9
+    */
+    static uint8_t last = 0xff;
+    if (last != pin)
+    {
+        // Reset the ADC to init all regs
+        uint32_t peripheral = 0;
+        uint8_t pin_index = 0;   // Pin num
+        uint8_t adc_channel = 0; // Channel
+        GPIO_TypeDef *gpio;
+        switch (pin)
+        {
+        case A2: // A0
+            peripheral = RCC_APB2Periph_GPIOA;
+            gpio = GPIOA;
+            pin_index = 2;
+            adc_channel = 0;
+            break;
+
+        case A1: // A1
+            peripheral = RCC_APB2Periph_GPIOA;
+            gpio = GPIOA;
+            pin_index = 1;
+            adc_channel = 1;
+            break;
+
+        case C4: // A2
+            peripheral = RCC_APB2Periph_GPIOC;
+            gpio = GPIOC;
+            pin_index = 4;
+            adc_channel = 2;
+            break;
+
+        case D2: // A3
+            peripheral = RCC_APB2Periph_GPIOD;
+            gpio = GPIOD;
+            pin_index = 2;
+            adc_channel = 3;
+            break;
+
+        case D3: // A4
+            peripheral = RCC_APB2Periph_GPIOD;
+            gpio = GPIOD;
+            pin_index = 3;
+            adc_channel = 4;
+            break;
+
+        case D5: // A5
+            peripheral = RCC_APB2Periph_GPIOD;
+            gpio = GPIOD;
+            pin_index = 5;
+            adc_channel = 5;
+            break;
+
+        case D6: // A6
+            peripheral = RCC_APB2Periph_GPIOD;
+            gpio = GPIOD;
+            pin_index = 6;
+            adc_channel = 6;
+            break;
+
+        case D4: // A7
+            peripheral = RCC_APB2Periph_GPIOD;
+            gpio = GPIOD;
+            pin_index = 4;
+            adc_channel = 7;
+            break;
+
+        case ADC_CH_REF: // A8
+            peripheral = 0;
+            gpio = NULL;
+            pin_index = 8;
+            adc_channel = 8;
+            break;
+
+        case ADC_CH_CAL: // A9
+            peripheral = 0;
+            gpio = NULL;
+            pin_index = 9;
+            adc_channel = 9;
+            break;
+        default:
+            return 0;
+            break;
+        }
+
+        // ADCCLK = 24 MHz => RCC_ADCPRE = 0: divide by 2
+        RCC->CFGR0 &= ~(0x1F << 11);
+        RCC->APB2PCENR |= peripheral | RCC_APB2Periph_ADC1;
+
+        // PXi is analog input chl 7
+        if (gpio)
+            gpio->CFGLR &= ~(0xf << (4 * pin_index)); // CNF = 00: Analog, MODE = 00: Input
+
+        // Reset the ADC to init all regs
+        RCC->APB2PRSTR |= RCC_APB2Periph_ADC1;
+        RCC->APB2PRSTR &= ~RCC_APB2Periph_ADC1;
+
+        // Set up single conversion on chl 7
+        ADC1->RSQR1 = 0;
+        ADC1->RSQR2 = 0;
+        ADC1->RSQR3 = adc_channel; // A0通道
+
+        // set sampling time for chl 7
+        ADC1->SAMPTR2 &= ~(ADC_SMP0 << (3 * 7));
+        ADC1->SAMPTR2 |= 7 << (3 * 7); // 0:7 => 3/9/15/30/43/57/73/241 cycles
+
+        // turn on ADC and set rule group to sw trig
+        ADC1->CTLR2 |= ADC_ADON | ADC_EXTSEL;
+
+        // Reset calibration
+        ADC1->CTLR2 |= ADC_RSTCAL;
+        while (ADC1->CTLR2 & ADC_RSTCAL)
+            ;
+
+        // Calibrate
+        ADC1->CTLR2 |= ADC_CAL;
+        while (ADC1->CTLR2 & ADC_CAL)
+            ;
+        last = pin;
+    }
+
+    // should be ready for SW conversion now
+
+    ADC1->CTLR2 |= ADC_SWSTART;
+
+    // wait for conversion complete
+    while (!(ADC1->STATR & ADC_EOC))
+        ;
+
+    // get result
+    return ADC1->RDATAR;
+}

examples/CH32V003-ADC/CH32V003-ADC.ino

@@ -0,0 +1,33 @@
+#include <stdio.h>
+#include <Arduino.h>
+
+
+
+uint8_t adc_pins[] = {
+    A2,         // A0
+    A1,         // A1
+    C4,         // A2
+    D2,         // A3
+    D3,         // A4
+    D5,         // A5
+    D6,         // A6
+    D4,         // A7
+    ADC_CH_REF, // A8
+    ADC_CH_CAL, // A9
+};
+
+
+void setup()
+{
+
+}
+
+void loop()
+{
+  printf("------------\n");
+  for (int i = 0; i < sizeof(adc_pins); i++)
+  {
+    printf("ADC %d V=%d\n", i, analogRead(adc_pins[i]));
+  }
+  delay(3000);
+}