CurrentRanger_R3: add preference to timestamp samples

For USB and BT serial data output add options to preface each sample
with the system time at which it was taken, in microseconds.  This
mitigates the loss of information when the sample rate is changed
dynamically.

Be aware that the counter will wrap at 2^32 us, so relative
calculations should be done using unsigned 32-bit operations.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>

Author: pabigot

CurrentRanger_R3.ino

@@ -114,6 +114,8 @@ Adafruit_FreeTouch qt[3] = {
 #define LOGGING_FORMAT_ADC      4 //raw output for each range (0..4095)
 //***********************************************************************************************************
 #define PREFERENCE_MU_SAMPLERATE 0x01  // default BIAS
+#define PREFERENCE_USB_TIMESTAMP 0x02  // timestamp serial samples
+#define PREFERENCE_BT_TIMESTAMP 0x04   // timestamp bluetooth samples
 //***********************************************************************************************************
 static const char *const loggingFormat_str[] = {
   [LOGGING_FORMAT_EXPONENT] = "exp (1.23E-3 = 123 mA)",
@@ -298,6 +300,7 @@ uint32_t oledInterval=0, lpfInterval=0, modeInterval=0, autorangeInterval=0, btI
 byte LPF=0, BIAS=0, AUTORANGE=0, SRADJUST=0;
 byte readVbatLoop=0;
 float vbat=0, VOUT=0;
+unsigned long readMicros;
 float read1=0,read2=0,readDiff=0;
 bool rangeSwitched=false;
 #define RANGE_MA rangeUnit=='m'
@@ -464,6 +467,14 @@ void loop()
         USB_LOGGING_ENABLED =! USB_LOGGING_ENABLED;
         Serial.println(USB_LOGGING_ENABLED ? "USB_LOGGING_ENABLED" : "USB_LOGGING_DISABLED");
         break;
+      case 'U': //toggle USB timestamping
+        PREFERENCES ^= PREFERENCE_USB_TIMESTAMP;
+        eeprom_PREFERENCES.write(PREFERENCES);
+        if (!(PREFERENCES & PREFERENCE_USB_TIMESTAMP)) {
+          Serial.print("NO ");
+        }
+        Serial.println("USB sample timestamps");
+        break;
       case 't': //toggle touchpad serial output debug info
         TOUCH_DEBUG_ENABLED =! TOUCH_DEBUG_ENABLED;
         Serial.println(TOUCH_DEBUG_ENABLED ? "TOUCH_DEBUG_ENABLED" : "TOUCH_DEBUG_DISABLED");
@@ -481,6 +492,14 @@ void loop()
         BT_LOGGING_ENABLED =! BT_LOGGING_ENABLED;
         Serial.println(BT_LOGGING_ENABLED ? "BT_LOGGING_ENABLED" : "BT_LOGGING_DISABLED");
         break;
+      case 'B': //toggle BT timestamping
+        PREFERENCES ^= PREFERENCE_BT_TIMESTAMP;
+        eeprom_PREFERENCES.write(PREFERENCES);
+        if (!(PREFERENCES & PREFERENCE_BT_TIMESTAMP)) {
+          Serial.print("NO ");
+        }
+        Serial.println("BT sample timestamps");
+        break;
       case 'f': //cycle through output logging formats
         if (++LOGGING_FORMAT>LOGGING_FORMAT_ADC) LOGGING_FORMAT=LOGGING_FORMAT_EXPONENT;
         eeprom_LOGGINGFORMAT.write(LOGGING_FORMAT);
@@ -535,6 +554,9 @@ void loop()
     if (!AUTORANGE) readVOUT();
     VOUT = readDiff*ldoOptimized*(BIAS?1:OUTPUT_CALIB_FACTOR);
     VOUTCalculated=true;
+    if (PREFERENCES & PREFERENCE_USB_TIMESTAMP) {
+      Serial.print(readMicros); Serial.print(" ");
+    }
     if(LOGGING_FORMAT == LOGGING_FORMAT_EXPONENT) { Serial.print(VOUT); Serial.print("e"); Serial.println(RANGE_NA ? -9 : RANGE_UA ? -6 : -3); } else
     if(LOGGING_FORMAT == LOGGING_FORMAT_NANOS) Serial.println(VOUT * (RANGE_NA ? 1 : RANGE_UA ? 1000 : 1000000)); else
     if(LOGGING_FORMAT == LOGGING_FORMAT_MICROS) Serial.println(VOUT * (RANGE_NA ? 0.001 : RANGE_UA ? 1 : 1000)); else
@@ -556,6 +578,9 @@ void loop()
       VOUT = readDiff*ldoOptimized*(BIAS?1:OUTPUT_CALIB_FACTOR);
       VOUTCalculated=true;
     }
+    if (PREFERENCES & PREFERENCE_BT_TIMESTAMP) {
+      SerialBT.print(readMicros); SerialBT.print(" ");
+    }
     if(LOGGING_FORMAT == LOGGING_FORMAT_EXPONENT) { SerialBT.print(VOUT); SerialBT.print("e"); SerialBT.println(RANGE_NA ? -9 : RANGE_UA ? -6 : -3); } else
     if(LOGGING_FORMAT == LOGGING_FORMAT_NANOS) SerialBT.println(VOUT * (RANGE_NA ? 1 : RANGE_UA ? 1000 : 1000000)); else
     if(LOGGING_FORMAT == LOGGING_FORMAT_MICROS) SerialBT.println(VOUT * (RANGE_NA ? 0.001 : RANGE_UA ? 1 : 1000)); else
@@ -822,6 +847,7 @@ void setupADC() {
 
 int adcRead(byte ADCpin) { return (int)analogRead(ADCpin); }
 void readVOUT() {
+  readMicros = micros();
   readDiff = adcRead(SENSE_OUTPUT) - adcRead(SENSE_GNDISO);
 
   if (!analog_ref_half && readDiff > RANGE_SWITCH_THRESHOLD_LOW && readDiff < RANGE_SWITCH_THRESHOLD_HIGH/3)
@@ -903,16 +929,24 @@ void printCalibInfo() {
   Serial.println((PREFERENCES & PREFERENCE_MU_SAMPLERATE)
           ? "toggle samplerate adjust"
           : "toggle offset enable");
+  Serial.print("USB timestamp: ");
+  Serial.println((PREFERENCES & PREFERENCE_USB_TIMESTAMP)
+          ? "on" : "off");
+  Serial.print("BT timestamp: ");
+  Serial.println((PREFERENCES & PREFERENCE_BT_TIMESTAMP)
+          ? "on" : "off");
 }
 void printSerialMenu() {
   Serial.println("\r\nUSB serial commands:");
   Serial.println("a = toggle Auto-Off function");
   Serial.print  ("b = toggle BT/serial logging (");Serial.print(SERIAL_UART_BAUD);Serial.println("baud)");
+  Serial.println("B = toggle timestamp on BT/serial output [PREF]");
   Serial.println("f = cycle serial logging formats (exponent,nA,uA,mA/raw-ADC) [PREF]");
   Serial.println("g = toggle GPIO range indication (SCK=mA,MISO=uA,MOSI=nA)");
   Serial.println("o = toggle touchpad offset (bias) / samplerate selection [PREF]");
   Serial.println("t = toggle touchpad serial output debug info");
   Serial.println("u = toggle USB/serial logging");
+  Serial.println("U = toggle timestamp in USB/serial output [PREF]");
   Serial.println("+ = increase mode value");
   Serial.println("- = decrease mode value");
   Serial.println("? = Print this menu and calib info");