From 1ec0f63696c78c77e62f682a6ca242e01295aa26 Mon Sep 17 00:00:00 2001
From: Andy Killorin <37423245+Speedy6451@users.noreply.github.com>
Date: Thu, 3 Apr 2025 11:30:58 -0400
Subject: [PATCH] voltage scaling

---
 main.c | 34 +++++++++++++++++++++++++++++++---
 1 file changed, 31 insertions(+), 3 deletions(-)

diff --git a/main.c b/main.c
index e2e2f12..1a8e09b 100644
--- a/main.c
+++ b/main.c
@@ -35,6 +35,21 @@ volatile uint8_t drawRequested = 1;
 #define WIDTH LCD_HORIZONTAL_MAX
 #define PIXELS_PER_DIV 20
 
+#define VIN_RANGE 3.3 // volts
+#define ADC_BITS 12
+#define ADC_OFFSET 30
+
+#define VOLTAGE_SCALES 5
+const char * const gVoltageScaleStr[VOLTAGE_SCALES] = {
+"100 mV", "200 mV", "500 mV", " 1 V", " 2 V"
+};
+
+const float gVoltageScale[VOLTAGE_SCALES] = {
+    0.1, 0.2, 0.5, 1., 2.
+};
+
+int RisingTrigger(void);
+
 // start a pwm test signal
 void start_signal() {
   // configure M0PWM2, at GPIO PF2, BoosterPack 1 header C1 pin 2
@@ -87,14 +102,22 @@ int main(void) {
     ButtonInit();
     IntMasterEnable();
 
+    uint8_t voltage_scale = 0;
+
     while (true) {
         // handle buttons
         Button button = (Button) 0;
         while (fifo_get(&button)) {
             switch (button) {
-                case S2:
+                case S2: // draw
                     drawRequested = 1;
                     break;
+                case Up: // next scale
+                    voltage_scale = (voltage_scale + 1) % VOLTAGE_SCALES;
+                    break;
+                case Down: // previous scale
+                    voltage_scale = (voltage_scale + VOLTAGE_SCALES - 1) % VOLTAGE_SCALES;
+                    break;
             }
         }
 
@@ -130,9 +153,15 @@ int main(void) {
             drawRequested = 0;
         }
 
+        GrContextForegroundSet(&sContext, ClrWheat);
+        GrStringDraw(&sContext, gVoltageScaleStr[voltage_scale], /*length*/ -1, /*x*/ 0, /*y*/ 0, /*opaque*/ false);
+
+        float fVoltsPerDiv = gVoltageScale[voltage_scale];
+        float fScale = (VIN_RANGE * PIXELS_PER_DIV)/((1 << ADC_BITS) * fVoltsPerDiv);
+
         GrContextForegroundSet(&sContext, ClrPink);
         for(j=0; j<LOCAL_BUF_LEN; j++) {
-            #define TRANSPOSE(x) (HEIGHT/2) - (x >> 6) // reduce from twelve to six bits, then flip and center
+            #define TRANSPOSE(x) (HEIGHT/2) - (int)roundf(fScale * ((int)x - ADC_OFFSET));
             uint32_t upper,lower, current, last;
 
             if (j==0) {
@@ -191,7 +220,6 @@ int main(void) {
 
 int RisingTrigger(void) // search for rising edge trigger
 {
-    #define ADC_OFFSET 20
     int x = gADCBufferIndex - (WIDTH / 2); // half screen width
     int x_stop = x - ADC_BUFFER_SIZE/2;
     for (; x > x_stop; x--) {