Change some ADC parameters

Still getting ~64 reads per update cycle, but sampling a little slower. After doing some testing it may - or may not - result in more stability of readings.

Doubled the count of averaged readings.

include/adc.h

@@ -14,11 +14,11 @@
 
 
 #define ADC_CHANNELS	5
-#define ADC_HISTLEN		16
+#define ADC_HISTLEN		32
 
 
 
-extern uint16_t adc_avg[ADC_CHANNELS];
+extern uint32_t adc_avg[ADC_CHANNELS];
 
 
 

src/adc.c

@@ -9,12 +9,12 @@
  * voltage - only the analog supply can be the reference.
  * 
  * because most inputs are high impedance, which is not ideal,
- * sampling time is increased. this results in a final ADC sample rate
+ * sampling time is increased. this value may change in the future.
- * of about 33KHz, still well beyond what is needed in this application.
- * this value may change in the future.
  * 
  * note: attempted to use DMA for this and scanning all channels
  * at once, but that didn't work. would not reliably read channels.
+ * the example does 32bit transfers and I was doing 16bit;
+ * maybe there's some issue with that.
  * tried many different variations and it just wasn't working.
  * because of this I moved to using interrupt and the built-in
  * wait mode just in case things went slow.
@@ -30,7 +30,7 @@
 
 
 
-#define SAMPLE_TIME     LL_ADC_SAMPLINGTIME_239CYCLES_5
+#define SAMPLE_TIME     LL_ADC_SAMPLINGTIME_41CYCLES_5
 
 #define ADC_SEQ_RDY		0xff
 #define ADC_SEQ_STARTUP	0xfe
@@ -44,7 +44,7 @@
 static uint16_t adc_read[ADC_CHANNELS];
 static uint16_t adc_hist[ADC_CHANNELS][ADC_HISTLEN];
 
-uint16_t adc_avg[ADC_CHANNELS];
+uint32_t adc_avg[ADC_CHANNELS];
 
 static uint8_t adc_seq = 0;
 static uint8_t adc_idx = ADC_HISTLEN + 1;
@@ -70,6 +70,9 @@ void adc_init()
 	// with wait mode (anti-overrun) active
 	ADC1->CFGR1 = ADC_CFGR1_OVRMOD | ADC_CFGR1_WAIT;
 
+	// default clock
+	ADC1->CFGR2 = 0;
+
     // configure scan channels, sampling time (11 = temp, 12 = vrefint)
     ADC1->SMPR = SAMPLE_TIME;
 	ADC1->CHSELR = CONF_SET1_AN | PROBE_AN | 		// note: SET1 and VREFEXT are
@@ -160,6 +163,9 @@ uint8_t adc_next()
 		// wait for calibration to complete, if started
 		while (ADC1->CR & ADC_CR_ADCAL) {};
 
+		// set ADC clock to 4MHz
+		ADC1->CFGR2 = LL_ADC_CLOCK_ASYNC_HSI_DIV2;
+
 		// do our first round of conversions
 		adc_go();
 
@@ -185,7 +191,7 @@ uint8_t adc_next()
 				for (j = 0; j < ADC_HISTLEN; j++) {
 					adc_avg[i] += adc_hist[i][j];
 				}
-				adc_avg[i] >>= 4;
+				adc_avg[i] /= ADC_HISTLEN;
 			}
 
 			// check vref to determine if we need to recalibrate

src/main.c

@@ -116,7 +116,7 @@ int main()
 
     while (1) {
         // run LED programs out of interrupt context at 256Hz
-        if ((ctr & 0xf) == 0) {
+        if (!(ctr & 0xf)) {
             if (userio_get_mode() == MODE_FUN) {
                 rgbprog_run();
             }
@@ -130,6 +130,8 @@ int main()
 /*
  * main application interrupt
  */
+uint16_t adc_ctr = 0;           // count ADC cycles
+volatile uint16_t adc_sec;      // ADC cycles per second (used w/debugger)
 
 void SysTick_Handler(void)
 {
@@ -144,16 +146,21 @@ void SysTick_Handler(void)
     ctr &= 0xfff;
     if (!ctr) {
         uptime++;
+        adc_sec = adc_ctr;
+        adc_ctr = 0;
     }
 
-    // run main logic at 1024Hz
+    // run main logic at 2048Hz
-    if (!(ctr & 0x3)) {
+    if (!(ctr & 0x1)) {
         // shifted counter for use in the program
-        cs = ctr >> 2;
+        cs = ctr >> 1;
 
 		// adc tested to result in about 61 reads/second
 		if (!adc_next()) {
 			// adc has new computed results
+            adc_ctr++;
+
+            // start using ADC results only after the first cycle
 			if (uptime || cs) {
                 // figure out knobs, buttons, switches
 				userio_parse();