saul_adc: Add scaling option

boards/frdm-k64f/Makefile.dep

@@ -1,5 +1,6 @@
 ifneq (,$(filter saul_default,$(USEMODULE)))
   USEMODULE += saul_adc
+  USEMODULE += analog_util
 endif
 
 include $(RIOTCPU)/kinetis/Makefile.dep

boards/frdm-k64f/include/adc_params.h

@@ -49,7 +49,18 @@ static const  saul_adc_params_t saul_adc_params[] =
     { .name = "ADC1_DP1", .line = ADC_LINE(15), .res  = ADC_RES_16BIT, },
     { .name = "ADC1_DM1", .line = ADC_LINE(16), .res  = ADC_RES_16BIT, },
     { .name = "ADC1_DP1-ADC1_DM1", .line = ADC_LINE(17), .res  = ADC_RES_16BIT, },
-    { .name = "coretemp", .line = ADC_LINE(18), .res  = ADC_RES_16BIT, },
+    {
+        .name = "coretemp", .line = ADC_LINE(18), .res  = ADC_RES_16BIT,
+        .unit = UNIT_TEMP_C, .scale = -1,
+        /* Scaling the temperature sensor voltage to units of 0.1 Celsius, this
+         * depends on several numbers found in the data sheet as well as the
+         * analog reference voltage (VREFH), which is 3.3 V on FRDM-K64F.
+         * These numbers yield a full range of -1570..466 Cel, which is
+         * unrealistic, but because of the physical limits, the sensor will ever
+         * only use a small range of that interval. */
+        .val_min = (int32_t)(250 - ((   0 - 716) / 1.62) * 10),
+        .val_max = (int32_t)(250 - ((3300 - 716) / 1.62) * 10),
+    },
     { .name = "corebandgap", .line = ADC_LINE(19), .res  = ADC_RES_16BIT, },
 };
 

boards/mulle/Makefile.dep

@@ -18,6 +18,7 @@ USEMODULE += periph_rtt
 ifneq (,$(filter saul_default,$(USEMODULE)))
   USEMODULE += saul_gpio
   USEMODULE += saul_adc
+  USEMODULE += analog_util
 endif
 
 include $(RIOTCPU)/kinetis/Makefile.dep

boards/mulle/include/adc_params.h

@@ -32,9 +32,16 @@ extern "C" {
 static const  saul_adc_params_t saul_adc_params[] =
 {
     {
-        .name = "k60temp",
-        .line = ADC_LINE(0),
-        .res  = ADC_RES_16BIT,
+        .name = "coretemp", .line = ADC_LINE(0), .res  = ADC_RES_16BIT,
+        .unit = UNIT_TEMP_C, .scale = -1,
+        /* Scaling the temperature sensor voltage to units of 0.1 Celsius, this
+         * depends on several numbers found in the data sheet as well as the
+         * analog reference voltage (VREFH), which is 3.3 V on FRDM-K64F.
+         * These numbers yield a full range of -1570..466 Cel, which is
+         * unrealistic, but because of the physical limits, the sensor will ever
+         * only use a small range of that interval. */
+        .val_min = (int32_t)(250 - ((   0 - 716) / 1.62) * 10),
+        .val_max = (int32_t)(250 - ((3300 - 716) / 1.62) * 10),
     },
     {
         .name = "k60vrefsh",
@@ -65,11 +72,17 @@ static const  saul_adc_params_t saul_adc_params[] =
         .name = "Vbat",
         .line = MULLE_VBAT_ADC_LINE,
         .res  = ADC_RES_16BIT,
+        .unit = UNIT_V, .scale = -3,
+        .val_min = 0,
+        .val_max = (3300 * 2), /* Compensate for the ADC input connected to Vbat/2 */
     },
     {
         .name = "Vchr",
         .line = MULLE_VCHR_ADC_LINE,
         .res  = ADC_RES_16BIT,
+        .unit = UNIT_V, .scale = -3,
+        .val_min = 0,
+        .val_max = (3300 * 2), /* Compensate for the ADC input connected to Vchr/2 */
     },
     {
         .name = "PGA0_DP",

drivers/include/saul/periph.h

@@ -60,6 +60,10 @@ typedef struct {
     const char *name;       /**< name of the device connected to this pin */
     adc_t line;             /**< ADC line to initialize and expose */
     adc_res_t res;          /**< ADC resolution */
+    int32_t val_min;        /**< value corresponding to an ADC raw value of 0 */
+    int32_t val_max;        /**< value corresponding to the maximum ADC reading */
+    uint8_t unit;           /**< phydat unit */
+    int8_t  scale;          /**< phydat scale */
 } saul_adc_params_t;
 #endif /* MODULE_SAUL_ADC */
 

drivers/saul/adc_saul.c

@@ -24,11 +24,14 @@
 #include "saul/periph.h"
 #include "phydat.h"
 #include "periph/adc.h"
+#if MODULE_ANALOG_UTIL
+#include "analog_util.h"
+#endif
 
-
+/* Unscaled version of sampling driver */
 static int read_adc(const void *dev, phydat_t *res)
 {
-    const saul_adc_params_t *params = *((const saul_adc_params_t **)dev);
+    const saul_adc_params_t *params = (const saul_adc_params_t *)dev;
     res->val[0] = adc_sample(params->line, params->res);
     memset(&(res->val[1]), 0, 2 * sizeof(res->val[1]));
     /* Raw ADC reading has no unit */
@@ -42,3 +45,31 @@ const saul_driver_t adc_saul_driver = {
     .write = saul_notsup,
     .type = SAUL_SENSE_ANALOG,
 };
+
+/* Scaling version of sampling driver */
+#if MODULE_ANALOG_UTIL
+static int read_adc_scaled(const void *dev, phydat_t *res)
+{
+    const saul_adc_params_t *params = (const saul_adc_params_t *)dev;
+    int raw = adc_sample(params->line, params->res);
+    int32_t value = adc_util_map(raw, params->res, params->val_min, params->val_max);
+    res->val[0] = value;
+    memset(&(res->val[1]), 0, 2 * sizeof(res->val[1]));
+    res->unit = params->unit;
+    res->scale = params->scale;
+    return 1;
+}
+
+/**
+ * @brief   SAUL driver template
+ */
+#define ADC_SAUL_DRIVER_INSTANCE(saul_type, name) \
+    const saul_driver_t adc_saul_ ## name ## _driver = { \
+    .read = read_adc_scaled, \
+    .write = saul_notsup, \
+    .type = saul_type, \
+}
+
+ADC_SAUL_DRIVER_INSTANCE(SAUL_SENSE_TEMP, temp);
+ADC_SAUL_DRIVER_INSTANCE(SAUL_SENSE_ANALOG, analog);
+#endif

sys/auto_init/saul/auto_init_adc.c

@@ -32,35 +32,58 @@
  */
 #define SAUL_ADC_NUMOF    (sizeof(saul_adc_params)/sizeof(saul_adc_params[0]))
 
-/**
- * @brief   Allocate memory for pointers to the ADC parameter structs
- *
- * We use this extra level of indirection to be able to keep the saul_adc_params
- * array const and residing in ROM.
- */
-static const saul_adc_params_t *saul_adcs[SAUL_ADC_NUMOF];
-
 /**
  * @brief   Memory for the registry entries
  */
 static saul_reg_t saul_reg_entries[SAUL_ADC_NUMOF];
 
 /**
- * @brief   Reference the driver struct
+ * @name    driver struct references
+ * @{
  */
 extern saul_driver_t adc_saul_driver;
+#if MODULE_ANALOG_UTIL
+extern saul_driver_t adc_saul_temp_driver;
+extern saul_driver_t adc_saul_analog_driver;
+#endif /* MODULE_ANALOG_UTIL */
+/** @} */
 
 void auto_init_adc(void)
 {
     for (unsigned i = 0; i < SAUL_ADC_NUMOF; i++) {
         const saul_adc_params_t *p = &saul_adc_params[i];
-        saul_adcs[i] = p;
 
         LOG_DEBUG("[auto_init_saul] initializing direct ADC #%u\n", i);
 
-        saul_reg_entries[i].dev = &saul_adcs[i];
+        /* discarding const qualifier of target type, the driver must only use
+         * it as if it is const though. */
+        saul_reg_entries[i].dev = (void *)p;
         saul_reg_entries[i].name = p->name;
+#if MODULE_ANALOG_UTIL
+        if (p->val_min != p->val_max) {
+            /* Apply scaling */
+            switch (p->unit) {
+                /* Pick the correct sensor type based on the unit */
+                case UNIT_TEMP_C:
+                case UNIT_TEMP_F:
+                case UNIT_TEMP_K:
+                    saul_reg_entries[i].driver = &adc_saul_temp_driver;
+                    break;
+                case UNIT_A:
+                case UNIT_V:
+                default:
+                    /* Fall back: use sensor type SAUL_SENSE_ANALOG */
+                    saul_reg_entries[i].driver = &adc_saul_analog_driver;
+                    break;
+            }
+        }
+        else {
+            /* Unscaled raw values */
+            saul_reg_entries[i].driver = &adc_saul_driver;
+        }
+#else /* MODULE_ANALOG_UTIL */
         saul_reg_entries[i].driver = &adc_saul_driver;
+#endif /* MODULE_ANALOG_UTIL */
         /* initialize the ADC line */
         adc_init(p->line);
         /* add to registry */