multiplexing over 9 channels

newcode/main.c

@@ -6,9 +6,11 @@
 #include <stddef.h>
 #include "yaMBSiavr.h"
 
-#define AVRG 1024
+#define AVRG 512
+
+volatile uint16_t adc_buffer[AVRG];
+volatile float ch_values[9];
 
-uint16_t adc_values[AVRG];
 
 void init_clk(void)
 {
@@ -37,7 +39,7 @@ void init_clk(void)
 void init_timer_100us(){
     TCC0.CTRLA |= TC_CLKSEL_DIV256_gc;
     TCC0.PER = 13; // ==> 9615Hz
-    TCC0.INTCTRLA |= TC_OVFINTLVL_MED_gc;
+    TCC0.INTCTRLA |= TC_OVFINTLVL_HI_gc;
 }
 
 void adc_init(void){
@@ -69,16 +71,17 @@ uint16_t adc_read(void){
 
 float avrg(uint16_t * values, uint16_t length){
     uint64_t res = 0;
-    for(uint16_t i=0; i < length; i++){
+    //ommit first and last sample
+    for(uint16_t i=1; i < length-1; i++){
         res += values[i];
     }
-    return (float)(res)/length;
+    return (float)(res)/(length-2);
 }
 
 void dma_init(void){
     DMA.CTRL = DMA_ENABLE_bm;
 
-    //DMA.CH0.CTRLB = DMA_CH_TRNINTLVL_LO_gc;
+    DMA.CH0.CTRLB = DMA_CH_TRNINTLVL_LO_gc;
 
     DMA.CH0.TRFCNT = AVRG * 2;
     DMA.CH0.CTRLA = DMA_CH_BURSTLEN_2BYTE_gc | DMA_CH_SINGLE_bm;
@@ -92,9 +95,9 @@ void dma_init(void){
     DMA.CH0.SRCADDR1 = (((uintptr_t)&ADCA.CH0.RES) >> 0x08) & 0xFF;
     DMA.CH0.SRCADDR2 = (((uintptr_t)&ADCA.CH0.RES) >> 0x0F) & 0xFF;
 
-    DMA.CH0.DESTADDR0 = ((uintptr_t)adc_values) & 0xFF;
-    DMA.CH0.DESTADDR1 = ((uintptr_t)adc_values >> 0x08) & 0xFF;
-    DMA.CH0.DESTADDR2 = ((uintptr_t)adc_values >> 0x0F) & 0xFF;
+    DMA.CH0.DESTADDR0 = ((uintptr_t)adc_buffer) & 0xFF;
+    DMA.CH0.DESTADDR1 = ((uintptr_t)adc_buffer >> 0x08) & 0xFF;
+    DMA.CH0.DESTADDR2 = ((uintptr_t)adc_buffer >> 0x0F) & 0xFF;
 
     DMA.CH0.ADDRCTRL = DMA_CH_SRCRELOAD_BURST_gc | DMA_CH_DESTRELOAD_TRANSACTION_gc | DMA_CH_SRCDIR_INC_gc | DMA_CH_DESTDIR_INC_gc;
 
@@ -106,12 +109,7 @@ void modbusGet(void) {
     {
         switch(rxbuffer[1]) {
             case fcReadHoldingRegisters: ;
-                float tmp[4];
-                tmp[0] = avrg(adc_values, AVRG) - 170;
-                tmp[1] = (tmp[0])/ 3926 * 1.95;
-                tmp[2] = (tmp[1]*980)/(3.3-tmp[1]);
-                tmp[3] = (tmp[2]-100)/0.3927;
-                modbusExchangeRegisters(tmp, 0, 8);
+                modbusExchangeRegisters(ch_values, 0, 18);
                 break;
             default:
                 modbusSendException(ecIllegalFunction);
@@ -149,3 +147,25 @@ int main(void){
 ISR(TCC0_OVF_vect){
     modbusTickTimer();
 }
+
+ISR(DMA_CH0_vect){
+    static uint8_t pin = 0;
+
+    DMA.INTFLAGS |= DMA_CH0TRNIF_bm; // clear flag
+    DMA.CH0.TRIGSRC = DMA_CH_TRIGSRC_OFF_gc;
+    ADCA.CTRLB = 0; // stop ADC
+
+    uint8_t old_pin = pin;
+    pin=(pin+1)%1;
+    ADCA.CH0.MUXCTRL = pin << ADC_CH_MUXPOS_gp; // give MUX time to switch during averaging
+    float temp = avrg(adc_buffer, AVRG);
+
+    temp = temp - 170;
+    temp = (temp)/ 3926 * 1.95;
+    temp = (temp*993.5)/(3.3-temp);
+    temp = (temp-100)/0.3927;
+    ch_values[old_pin] = temp;
+
+    DMA.CH0.TRIGSRC = DMA_CH_TRIGSRC_ADCA_CH0_gc;
+    ADCA.CTRLB = ADC_FREERUN_bm; // start ADC again
+}