ADC

lis3dh.c

@@ -24,6 +24,7 @@ int lis3dh_init(lis3dh_t *lis3dh) {
     /* zero device struct */
     memset(&lis3dh->acc, 0, sizeof lis3dh->acc);
     memset(&lis3dh->cfg, 0, sizeof lis3dh->cfg);
+    memset(&lis3dh->adc, 0, sizeof lis3dh->adc);
 
     lis3dh->cfg.fifo.mode = 0xFF; /* in use if neq 0xFF */
     lis3dh->cfg.fifo.fth = 31; /* default watermark level. */
@@ -305,8 +306,8 @@ int lis3dh_read_fifo(lis3dh_t *lis3dh, struct lis3dh_fifo_data *fifo) {
     scale = 6;
     sens = acc_sensitivity(lis3dh->cfg.mode, lis3dh->cfg.range);
 
-    /* fifo buffer is max 32 */
-    fifo->size = lis3dh->cfg.fifo.fth > 32 ? 32 : lis3dh->cfg.fifo.fth;
+    /* fifo buffer is max 31 */
+    fifo->size = lis3dh->cfg.fifo.fth > 31 ? 31 : lis3dh->cfg.fifo.fth;
 
     /* must set MSbit of the address to multi-read and 
        have the device auto-increment the address.
@@ -353,6 +354,7 @@ int lis3dh_reference(lis3dh_t *lis3dh) {
     uint8_t res;
     return lis3dh->dev.read(REG_REFERENCE, &res, 1);
 }
+
 /* reset user regs and reload trim params */
 int lis3dh_reset(lis3dh_t *lis3dh) {
     int err = 0;
@@ -383,5 +385,30 @@ int lis3dh_reset(lis3dh_t *lis3dh) {
     err |= lis3dh->dev.write(REG_ACT_THS, 0x00);
     err |= lis3dh->dev.write(REG_ACT_DUR, 0x00);
     
+    return err;
+}
+
+/* read all 3 ADCs and convert readings depending on power mode
+   st 1 LSb is equal to 1 millivolt */
+int lis3dh_read_adc(lis3dh_t *lis3dh) {
+    uint8_t data[6];
+    int err = 0;
+    uint8_t shift;
+    float divisor;
+    /* read adc{1,2,3} LSB and MSB */
+    err |= lis3dh->dev.read(REG_OUT_ADC1_L | 0x80, data, 6);
+
+    if (lis3dh->cfg.mode == LIS3DH_MODE_LP) {
+        shift = 8;
+        divisor = 256.0;
+    } else {
+        shift = 6;
+        divisor = 1024.0;
+    }
+
+    lis3dh->adc.adc1 = 1200.0 + (400.0 * (float)(((int16_t)(data[1] | (data[0] << 8))) >> shift) / divisor); 
+    lis3dh->adc.adc2 = 1200.0 + (400.0 * (float)(((int16_t)(data[3] | (data[2] << 8))) >> shift) / divisor); 
+    lis3dh->adc.adc3 = 1200.0 + (400.0 * (float)(((int16_t)(data[5] | (data[4] << 8))) >> shift) / divisor); 
+
     return err;
 }

lis3dh.h

@@ -173,8 +173,24 @@ struct lis3dh_config {
     uint8_t en_temp; /* enable temp sensor on ADC 3 */
 };
 
-/* data read not from FIFO is put here */
-struct lis3dh_acceleration {
+/* reads from internal ADCs. 
+ * Input range: 800 mV to 1600 mV 
+ * Resolution:
+ *              8-bit in LP mode
+ *             10-bit in normal and in HR mode.
+ * Sampling frequency:
+ *              same as ODR
+ * Output:
+ *            actual value in mV
+ */
+struct lis3dh_adc {
+    float adc1;
+    float adc2;
+    float adc3;
+};
+
+/* accel data not read from FIFO is put here */
+struct lis3dh_accel {
     float x;
     float y;
     float z;
@@ -183,7 +199,8 @@ struct lis3dh_acceleration {
 struct lis3dh {
     struct lis3dh_device dev;
     struct lis3dh_config cfg;
-    struct lis3dh_acceleration acc;
+    struct lis3dh_accel  acc;
+    struct lis3dh_adc    adc;
 };
 
 typedef struct lis3dh lis3dh_t;
@@ -207,5 +224,6 @@ int lis3dh_clear_int1(lis3dh_t *lis3dh);
 int lis3dh_clear_int2(lis3dh_t *lis3dh);
 int lis3dh_reference(lis3dh_t *lis3dh);
 int lis3dh_reset(lis3dh_t *lis3dh);
+int lis3dh_read_adc(lis3dh_t *lis3dh);
 
 #endif

main.c

@@ -35,7 +35,6 @@ int main() {
     lis.dev.sleep = usleep;
     lis.dev.deinit = i2c_deinit;
 
-
     /* initialise LIS3DH struct */
     if (lis3dh_init(&lis)) {
         quit("init()", &lis);
@@ -61,19 +60,21 @@ int main() {
     lis.cfg.pin1.latch = 1;
     lis.cfg.filter.mode = LIS3DH_FILTER_MODE_AUTORESET;
     lis.cfg.filter.cutoff = LIS3DH_FILTER_CUTOFF_8;
-    
 
+    lis.cfg.en_adc = 1;
+    
     /* write device config */
     if (lis3dh_configure(&lis)) {
         quit("configure()", &lis);
     }
     
     for(i=0; i<50; i++) {
-            /* wait for interrupt from LIS3DH */
+        /* wait for interrupt from LIS3DH */
         if (int_poll(GPIO_INTERRUPT_PIN_INT1)) {
             quit("int_poll()", &lis);
         }
 
+        /* clear latched interrupt on INT1 */
         if (lis3dh_clear_int1(&lis)) {
             quit("clear_int1()", &lis);
         }
@@ -83,10 +84,16 @@ int main() {
             quit("read_fifo()", &lis);
         }
 
+        /* read ADCs */
+        if (lis3dh_read_adc(&lis)) {
+            quit("read_adc()", &lis);
+        }
+
         for(k=0; k<fifo.size; k++) {
-            printf("%04.04f %04.04f %04.04f %04.04f\n",
+            printf("x: %04.04f y: %04.04f z: %04.04f mag: %04.04f ADC1:%.1f, ADC2:%.1f, ADC3:%.1f\n",
                 fifo.x[k], fifo.y[k], fifo.z[k],
-                mag(fifo.x[k], fifo.y[k], fifo.z[k]));
+                mag(fifo.x[k], fifo.y[k], fifo.z[k]),
+                lis.adc.adc1, lis.adc.adc2, lis.adc.adc3);
         }
 
     }