EIS: Add adjustable MCLK generated by XMEGA.

src/eis_shield/eis.c

@@ -40,7 +40,7 @@ void eis_measure_auto(uint32_t start, uint32_t increment, uint16_t n_increments,
      @param reference Reference connection setting
      @param result_buffer Buffer to store results
      */
-    
+    eis_set_mclk(0);
     ad5933_set_params(start, increment, n_increments, settle_cycles, pga_gain, output_range);
     eis_set_ref(reference);
     eis_set_gain(iv_gain);
@@ -57,8 +57,8 @@ void eis_measure_auto(uint32_t start, uint32_t increment, uint16_t n_increments,
 void eis_set_params(uint32_t start, uint32_t increment, uint16_t n_increments,
                      uint16_t settle_cycles, uint8_t pga_gain, uint8_t output_range,
                      uint8_t iv_gain, uint16_t attenuation, uint16_t offset,
-                     uint8_t reference){
-
+                     uint8_t reference, uint16_t mclk_div2){
+    eis_set_mclk(mclk_div2);
     ad5933_set_params(start, increment, n_increments, settle_cycles, pga_gain, output_range);
     eis_set_ref(reference);
     eis_set_gain(iv_gain);

src/eis_shield/eis.h

@@ -25,7 +25,7 @@ void eis_measure_auto(uint32_t start, uint32_t increment, uint16_t n_increments,
 void eis_set_params(uint32_t start, uint32_t increment, uint16_t n_increments,
                     uint16_t settle_cycles, uint8_t pga_gain, uint8_t output_range,
                     uint8_t iv_gain, uint16_t attenuation, uint16_t offset,
-                    uint8_t reference);
+                    uint8_t reference, uint16_t mclk_div2);
 cint16_t eis_measure_one(void);
 
 extern uint8_t eis_status;

src/eis_shield/eis_misc.c

@@ -8,6 +8,9 @@
 
 #include "eis_misc.h"
 #include "ds4550.h"
+#include "ad5933.h"
+#include <tc.h>
+#include <ioport.h>
 #include <delay.h>
 
 void eis_set_gain(uint8_t gain){
@@ -93,3 +96,22 @@ void eis_set_ref(uint8_t ref){
     return;
 }
 
+
+void eis_set_mclk(uint16_t div_2){
+    /**
+     * Set EIS mclk frequency. Send 0 to reset to internal MCLK (16.776 MHz)
+     *
+     * @param div_2 half of the desired frequency divider (f = 1/(2*div_2))
+     */
+    if (div_2 == 0)
+        ad5933_set_internal_mclk(1);
+    else {
+        ioport_set_pin_dir(IOPORT_CREATE_PIN(PORTC,2), IOPORT_DIR_OUTPUT);
+        tc_enable(&TCC0);
+        tc_set_wgm(&TCC0, TC_WG_FRQ);
+        tc_write_cc(&TCC0, TC_CCA, div_2-1);
+        tc_enable_cc_channels(&TCC0,TC_CCCEN);
+        tc_write_clock_source(&TCC0, TC_CLKSEL_DIV1_gc);
+        ad5933_set_internal_mclk(0);
+    }
+}

src/eis_shield/eis_misc.h

@@ -25,7 +25,10 @@
 #define EIS_REF_R2          2
 #define EIS_REF_PARALLEL    3
 
+#define EIS_MCLK_INT        16776000UL
+
 void eis_set_gain(uint8_t gain);
 void eis_set_ref(uint8_t ref);
+void eis_set_mclk(uint16_t div_2);
 
 #endif /* eis_misc_h */

src/experiment.c

@@ -118,11 +118,11 @@ void experiment_handler(char command){
         case 'I':
         {
             uint32_t start_f, increment_f;
-            uint16_t n_increments, settle_cycles, attenuation, offset;
+            uint16_t n_increments, settle_cycles, attenuation, offset, mclk_div2;
             uint8_t pga_gain, output_range, iv_gain, reference;
             
-            scanf("%lu%lu%u%u%hhu%hhu%hhu%u%u%hhu", &start_f, &increment_f, &n_increments, &settle_cycles,
-                  &pga_gain, &output_range, &iv_gain, &attenuation, &offset, &reference);
+            scanf("%lu%lu%u%u%hhu%hhu%hhu%u%u%hhu%u", &start_f, &increment_f, &n_increments, &settle_cycles,
+                  &pga_gain, &output_range, &iv_gain, &attenuation, &offset, &reference, &mclk_div2);
 
             
             struct result {
@@ -134,7 +134,7 @@ void experiment_handler(char command){
             
             pot_exp_start(); //Disconnect DStat from shield
             eis_set_params(start_f, increment_f, n_increments-1, settle_cycles, pga_gain, output_range,
-                             iv_gain, attenuation, offset, reference);
+                             iv_gain, attenuation, offset, reference, mclk_div2);
             
             while (eis_status != EIS_STATUS_DONE){
                 if (udi_cdc_is_rx_ready()){