nRF42: SAADC double buffering

- Double-buffer SAADC data - Make default sample duration take 5us instead of 3us - Set MAXCNT to 16 initially
TMRh20 · Nov 4, 2024 · 6285868 · 6285868
1 parent f3ab825
commit 6285868
Show file tree

Hide file tree

Showing 2 changed files with 22 additions and 12 deletions.
diff --git a/src/AutoAnalogAudio.h b/src/AutoAnalogAudio.h
@@ -267,13 +267,13 @@ class AutoAnalog
   int8_t gain;
 
   /**
-  * Enable I2S on nRF52
+  * Enable I2S and/or SAADC on nRF52
   * By default this is disabled (analog output using PWM)
   * 
   * @code
   * aaAudio.begin(1,1,3);
   * @endcode
-  * @param Set to 1 for I2S DAC, 2 for I2S ADC, 3 for both
+  * @param Set to 1 for I2S DAC, 2 for I2S ADC, 3 for both, 4 for SAADC only, 5 for SAADC + PWM Output, 6 for SAADC + I2S Output
   */
   uint8_t useI2S;
 

diff --git a/src/NRF52840/AutoAnalogAudio.cpp b/src/NRF52840/AutoAnalogAudio.cpp
@@ -324,29 +324,39 @@ void AutoAnalog::getADC(uint32_t samples){
 
     while(NRF_SAADC->EVENTS_END == 0){ }
 
+    if(!adcWhichBuf){
+      NRF_SAADC->RESULT.PTR = (uint32_t)adcBuf1;
+    }else{
+      NRF_SAADC->RESULT.PTR = (uint32_t)adcBuf0;
+    }
+    NRF_SAADC->RESULT.MAXCNT = samples;
+    NRF_SAADC->EVENTS_END = 0;
+    NRF_SAADC->TASKS_START = 1;
+
     if(adcBitsPerSample == 16){
       if(!adcWhichBuf){
         for(uint32_t i=0; i<samples; i++){
           adcBuffer16[i] = adcBuf0[i] << 2;
         }
-        NRF_SAADC->RESULT.PTR = (uint32_t)adcBuf1;
       }else{
         for(uint32_t i=0; i<samples; i++){
           adcBuffer16[i] = adcBuf1[i] << 2;
         }
-        NRF_SAADC->RESULT.PTR = (uint32_t)adcBuf0;
       }      
     }else
     if(adcBitsPerSample == 8){
-      for(uint32_t i=0; i<samples; i++){
-        adcBuffer[i] = adcBuf0[i] >> 6;
+      if(!adcWhichBuf){
+        for(uint32_t i=0; i<samples; i++){
+          adcBuffer[i] = adcBuf0[i] >> 6;
+        }
+      }else{
+        for(uint32_t i=0; i<samples; i++){
+          adcBuffer[i] = adcBuf1[i] >> 6;
+        }
       }
     }
     adcWhichBuf = !adcWhichBuf;
-
-    NRF_SAADC->RESULT.MAXCNT = samples;
-    NRF_SAADC->EVENTS_END = 0;
-    NRF_SAADC->TASKS_START = 1;
+
 
   }
 
@@ -622,13 +632,13 @@ if(useI2S >= 4 && useI2S <= 6){
   NRF_SAADC->CH[0].PSELP = dinPin << SAADC_CH_PSELP_PSELP_Pos;
   NRF_SAADC->CH[0].PSELN = dinPin << SAADC_CH_PSELN_PSELN_Pos;
   NRF_SAADC->CH[0].CONFIG = (SAADC_CH_CONFIG_RESP_VDD1_2 << SAADC_CH_CONFIG_RESP_Pos ) | SAADC_CH_CONFIG_GAIN_Gain4 << SAADC_CH_CONFIG_GAIN_Pos |
-  SAADC_CH_CONFIG_REFSEL_Internal << SAADC_CH_CONFIG_REFSEL_Pos | SAADC_CH_CONFIG_TACQ_3us << SAADC_CH_CONFIG_TACQ_Pos |
+  SAADC_CH_CONFIG_REFSEL_Internal << SAADC_CH_CONFIG_REFSEL_Pos | SAADC_CH_CONFIG_TACQ_5us << SAADC_CH_CONFIG_TACQ_Pos |
   SAADC_CH_CONFIG_MODE_Diff << SAADC_CH_CONFIG_MODE_Pos | SAADC_CH_CONFIG_BURST_Disabled << SAADC_CH_CONFIG_BURST_Pos;
   NRF_SAADC->RESOLUTION = SAADC_RESOLUTION_VAL_14bit << SAADC_RESOLUTION_VAL_Pos;
   NRF_SAADC->OVERSAMPLE = SAADC_OVERSAMPLE_OVERSAMPLE_Over2x << SAADC_OVERSAMPLE_OVERSAMPLE_Pos;
   NRF_SAADC->SAMPLERATE = 16000000 / 16000 / 2 | SAADC_SAMPLERATE_MODE_Timers << SAADC_SAMPLERATE_MODE_Pos;
   NRF_SAADC->RESULT.PTR = (uint32_t)adcBuf0;
-  NRF_SAADC->RESULT.MAXCNT = MAX_BUFFER_SIZE;
+  NRF_SAADC->RESULT.MAXCNT = 16;
   NRF_SAADC->ENABLE = true;
 
   NRF_SAADC->TASKS_CALIBRATEOFFSET = true;