samd21/adc: initial implementation

boards/samd21-xpro/Makefile.features

@@ -1,4 +1,5 @@
 # Put defined MCU peripherals here (in alphabetical order)
+FEATURES_PROVIDED += periph_adc
 FEATURES_PROVIDED += periph_cpuid
 FEATURES_PROVIDED += periph_gpio
 FEATURES_PROVIDED += periph_i2c

boards/samd21-xpro/include/periph_conf.h

@@ -267,6 +267,40 @@ static const spi_conf_t spi_config[] = {
 #define RTT_RUNSTDBY        (1)         /* Keep RTT running in sleep states */
 /** @} */
 
+/**
+ * @name ADC Configuration
+ * @{
+ */
+#define ADC_NUMOF                          (1U)
+#define ADC_0_EN                           1
+#define ADC_MAX_CHANNELS                   14
+/* ADC 0 device configuration */
+#define ADC_0_DEV                          ADC
+#define ADC_0_IRQ                          ADC_IRQn
+#define ADC_0_CHANNELS                     (3U)
+/**
+ * @brief ADC Channel Configuration
+ */
+typedef struct {
+    gpio_t pin;            /**< ADC channel pin */
+    uint32_t muxpos;       /**< ADC channel pin multiplexer value */
+} adc_channel_t;
+
+/* ADC 0 Default values */
+#define ADC_0_CLK_SOURCE                   0 /* GCLK_GENERATOR_0 */
+#define ADC_0_PRESCALER                    ADC_CTRLB_PRESCALER_DIV512
+static const adc_channel_t adc_channels[] = {
+    /* port, pin, muxpos */
+    {GPIO_PIN(PA, 10), ADC_INPUTCTRL_MUXPOS_PIN18},    /* EXT2, pin 3 */
+    {GPIO_PIN(PA, 11), ADC_INPUTCTRL_MUXPOS_PIN19},    /* EXT2, pin 4 */
+    {GPIO_PIN(PA, 2), ADC_INPUTCTRL_MUXPOS_PIN0}       /* EXT3, pin 3 */
+};
+
+#define ADC_0_NEG_INPUT                    ADC_INPUTCTRL_MUXNEG_GND
+#define ADC_0_GAIN_FACTOR_DEFAULT          ADC_INPUTCTRL_GAIN_1X
+#define ADC_0_REF_DEFAULT                  ADC_REFCTRL_REFSEL_INT1V
+/** @} */
+
 #ifdef __cplusplus
 }
 #endif

cpu/samd21/periph/adc.c

@@ -0,0 +1,145 @@
+/*
+ * Copyright (C) 2017 Dan Evans <photonthunder@gmail.com>
+ * Copyright (C) 2017 Travis Griggs <travisgriggs@gmail.com>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+#include <stdint.h>
+#include "cpu.h"
+#include "periph/gpio.h"
+#include "periph/adc.h"
+#include "periph_conf.h"
+#include "mutex.h"
+
+/* Only if we actually have any ADCs */
+#if ADC_NUMOF
+
+/* Prototypes */
+static bool _adc_syncing(void);
+static void _adc_powerOff(void);
+static int _adc_configure(uint32_t resolution);
+
+static mutex_t _lock = MUTEX_INIT;
+
+static inline void _prep(void)
+{
+    mutex_lock(&_lock);
+}
+
+static inline void _done(void)
+{
+    mutex_unlock(&_lock);
+}
+
+static bool _adc_syncing(void)
+{
+    if (ADC_0_DEV->STATUS.reg & ADC_STATUS_SYNCBUSY) {
+        return true;
+    }
+    return false;
+}
+
+static void _adc_powerOff(void)
+{
+    while (_adc_syncing()) {}
+    /* Disable */
+    ADC_0_DEV->CTRLA.reg &= ~ADC_CTRLA_ENABLE;
+    /* Reset */
+    ADC_0_DEV->CTRLA.reg |= ADC_CTRLA_SWRST;
+    /* Disable bandgap */
+    if (ADC_0_REF_DEFAULT == ADC_REFCTRL_REFSEL_INT1V) {
+        SYSCTRL->VREF.reg &= ~SYSCTRL_VREF_BGOUTEN;
+    }
+}
+
+static int _adc_configure(uint32_t resolution)
+{
+    while (_adc_syncing()) {}
+    /*  Disable ADC Module before init */
+    ADC_0_DEV->CTRLA.reg &= ~ADC_CTRLA_ENABLE;
+    /* Power On */
+    PM->APBCMASK.reg |= PM_APBCMASK_ADC;
+    if (ADC_0_DEV->CTRLA.reg & ADC_CTRLA_SWRST) {
+        _done();
+        return -1;
+    }
+    if (ADC_0_DEV->CTRLA.reg & ADC_CTRLA_ENABLE) {
+        _done();
+        return -1;
+    }
+    /* GCLK Setup */
+    GCLK->CLKCTRL.reg = (uint32_t)((GCLK_CLKCTRL_CLKEN | GCLK_CLKCTRL_GEN_GCLK0 | (ADC_GCLK_ID << GCLK_CLKCTRL_ID_Pos)));
+    /* Set Voltage Reference */
+    ADC_0_DEV->REFCTRL.reg = ADC_0_REF_DEFAULT;
+    /* Configure CTRLB Register HERE IS THE RESOLUTION SET! */
+    ADC_0_DEV->CTRLB.reg = ADC_0_PRESCALER | resolution;
+    /* Disable all interrupts */
+    ADC_0_DEV->INTENCLR.reg =
+        (1 << ADC_INTENCLR_SYNCRDY_Pos) |
+        (1 << ADC_INTENCLR_WINMON_Pos) |
+        (1 << ADC_INTENCLR_OVERRUN_Pos) |
+        (1 << ADC_INTENCLR_RESRDY_Pos);
+    /* Load the fixed device calibration constants */
+    ADC_0_DEV->CALIB.reg =
+        ADC_CALIB_BIAS_CAL((*(uint32_t*)ADC_FUSES_BIASCAL_ADDR >> ADC_FUSES_BIASCAL_Pos)) |
+        ADC_CALIB_LINEARITY_CAL((*(uint64_t*)ADC_FUSES_LINEARITY_0_ADDR >> ADC_FUSES_LINEARITY_0_Pos));
+    while (_adc_syncing()) {}
+    /* Enable bandgap if VREF is internal 1V */
+    if (ADC_0_REF_DEFAULT == ADC_REFCTRL_REFSEL_INT1V) {
+        SYSCTRL->VREF.reg |= SYSCTRL_VREF_BGOUTEN;
+    }
+    /*  Enable ADC Module */
+    ADC_0_DEV->CTRLA.reg |= ADC_CTRLA_ENABLE;
+    return 0;
+}
+
+int adc_init(adc_t line)
+{
+    _prep();
+    gpio_init(adc_channels[line].pin, GPIO_IN);
+    gpio_init_mux(adc_channels[line].pin, GPIO_MUX_B);
+    _done();
+    return 0;
+}
+
+int adc_sample(adc_t line, adc_res_t res)
+{
+    if (line >= ADC_0_CHANNELS) {
+        return -1;
+    }
+    uint32_t resolution;
+    switch (res) {
+        case ADC_RES_8BIT:
+            resolution = ADC_CTRLB_RESSEL_8BIT;
+            break;
+        case ADC_RES_10BIT:
+            resolution = ADC_CTRLB_RESSEL_10BIT;
+            break;
+        case ADC_RES_12BIT:
+            resolution = ADC_CTRLB_RESSEL_12BIT;
+            break;
+        default:
+            resolution = 0xFFFFFFFF;
+            return -1;
+    }
+    _prep();
+    if (_adc_configure(resolution) != 0) {
+        _done();
+        return -1;
+    }
+    ADC_0_DEV->INPUTCTRL.reg = ADC_0_GAIN_FACTOR_DEFAULT | adc_channels[line].muxpos | ADC_0_NEG_INPUT;
+    while (_adc_syncing()) {}
+    /* Start the conversion */
+    ADC_0_DEV->SWTRIG.reg = ADC_SWTRIG_START;
+    /* Wait for the result */
+    while (!(ADC_0_DEV->INTFLAG.reg & ADC_INTFLAG_RESRDY)) {}
+    int result = ADC_0_DEV->RESULT.reg;
+    _adc_powerOff();
+    _done();
+    return result;
+}
+
+#endif /* #if ADC_NUMOF */