Add eis_misc: functions for gain and reference selection.

src/eis_shield/eis_misc.c

+//
+//  eis_misc.c
+//  dstat-firmware
+//
+//  Created by Michael Dryden on 2017-03-02.
+//  Copyright © 2017 Michael Dryden. All rights reserved.
+//
+
+#include "eis_misc.h"
+#include "ds4550.h"
+
+void eis_set_gain(uint8_t gain){
+    /**
+     * Set EIS IV converter gain.
+     *
+     * @param gain Gain setting defined in eis_misc.h
+     */
+    switch (gain) {
+        case EIS_IV_GAIN_0:
+            ds4550_set_pins(0b110000110, 0b111000000);
+            break;
+        case EIS_IV_GAIN_100:
+            ds4550_set_pins(0b111000110, 0b111000000);
+            break;
+        case EIS_IV_GAIN_3k:
+            ds4550_set_pins(0b101000110, 0b111000000);
+            break;
+        case EIS_IV_GAIN_30k:
+            ds4550_set_pins(0b100000110, 0b111000000);
+            break;
+        case EIS_IV_GAIN_300k:
+            ds4550_set_pins(0b011000110, 0b111000000);
+            break;
+        case EIS_IV_GAIN_3M:
+            ds4550_set_pins(0b010000110, 0b111000000);
+            break;
+        case EIS_IV_GAIN_30M:
+            ds4550_set_pins(0b001000110, 0b111000000);
+            break;
+        case EIS_IV_GAIN_100M:
+            ds4550_set_pins(0b000000110, 0b111000000);
+            break;
+        default:
+            printf("#WAR: EIS: No gain provided\r\n");
+            break;
+    }
+    
+    return;
+}
+
+void eis_set_ref(uint8_t ref){
+    /**
+     * Set EIS reference resistor switches.
+     *
+     * @param ref Reference setting defined in eis_misc.h
+     */
+    switch (ref) {
+        case EIS_REF_CELL:
+            ds4550_set_pins(0b000000000, 0b000110000);
+            break;
+        case EIS_REF_R1:
+            ds4550_set_pins(0b000010000, 0b000110000);
+            break;
+        case EIS_REF_R2:
+            ds4550_set_pins(0b000100000, 0b000110000);
+            break;
+        case EIS_REF_PARALLEL:
+            ds4550_set_pins(0b000110000, 0b000110000);
+            break;
+            
+        default:
+            printf("#WAR: EIS: No reference set.\r\n");
+            break;
+    }
+    
+    return;
+}
+

src/eis_shield/eis_misc.h

+//
+//  eis_misc.h
+//  dstat-firmware
+//
+//  Created by Michael Dryden on 2017-03-02.
+//  Copyright © 2017 Michael Dryden. All rights reserved.
+//
+
+#ifndef eis_misc_h
+#define eis_misc_h
+
+#include <stdio.h>
+
+#define EIS_IV_GAIN_0       0
+#define EIS_IV_GAIN_100     1
+#define EIS_IV_GAIN_3k      2
+#define EIS_IV_GAIN_30k     3
+#define EIS_IV_GAIN_300k    4
+#define EIS_IV_GAIN_3M      5
+#define EIS_IV_GAIN_30M     6
+#define EIS_IV_GAIN_100M    7
+
+#define EIS_REF_CELL        0
+#define EIS_REF_R1          1
+#define EIS_REF_R2          2
+#define EIS_REF_PARALLEL    3
+
+void eis_set_gain(uint8_t gain);
+void eis_set_ref(uint8_t ref);
+
+#endif /* eis_misc_h */