1 files changed, 19 insertions, 2 deletions
diff --git a/firmware/drivers/adc-as3514.c b/firmware/drivers/adc-as3514.c
index 3b411a3..9a81a52 100644
--- a/firmware/drivers/adc-as3514.c
+++ b/firmware/drivers/adc-as3514.c
@@ -26,18 +26,35 @@
 /* Read 10-bit channel data */
 unsigned short adc_read(int channel)
 {
-    unsigned char buf[2];
+    unsigned short data = 0;
+
+    if ((unsigned)channel >= NUM_ADC_CHANNELS)
+        return 0;
 
     ascodec_lock();
 
     /* Select channel */
     ascodec_write(AS3514_ADC_0, (channel << 4));
+    /*
+     * The AS3514 ADC will trigger an interrupt when the conversion
+     * is finished, if the corresponding enable bit in IRQ_ENRD2
+     * is set.
+     * Previously the code did not wait and this apparently did
+     * not pose any problems, but this should be more correct.
+     * Without the wait the data read back may be completely or
+     * partially (first one of the two bytes) stale.
+     */
+    ascodec_wait_adc_finished();
+
 
+    /* Read data */
+    unsigned char buf[2] = { 0, 0 };
     ascodec_readbytes(AS3514_ADC_0, 2, buf);
+    data = (((buf[0] & 0x3) << 8) | buf[1]);
 
     ascodec_unlock();
 
-    return (((buf[0] & 0x3) << 8) | buf[1]);
+    return data;
 }
 
 void adc_init(void)