Gain range shifting resistor variable

Adds handling functions, a getter/setter, and updated gain calculations
for added a resistor in series with the Pot to shift the gain range.

There's a critical fix not yet released but in the master branch.
PlatformIO with Arduino-ESP8266>3.0 needs it for the library to
function.

geoscope/ADCModule.cpp

@@ -17,6 +17,7 @@ volatile uint32_t adcReadableTime_cycles = 0;
 #define potSSpin 5 // digital pot slave select pin
 
 MCP41xxx* gainPot = NULL;
+double gainShiftRatio = 0;
 
 
 const SPISettings adcConfig = SPISettings(0.8e6, MSBFIRST, SPI_MODE0);
@@ -93,21 +94,22 @@ void adcPoll() {
 void changeAmplifierGain(float val) {
 	amplifierGain = val;
 	static uint16_t potValue = 0;
-	static const unsigned int potSteps = UINT8_MAX;
+	static const uint16_t potSteps = UINT8_MAX;
 
-	if (val <= 1) {
+	if (val <= 1.0) {
 		gainPot->shutdown();
-		//minimum gain (1) comes by shutting down the 
+		//minimum gain (1) comes by shutting down the pot
 		amplifierGain = 1;
 	}
 	else {
 
 		// calculate the nearest gain resistor value
-		potValue = round(potSteps-(potSteps/val));
+		potValue = round(potSteps * (1-(1+gainShiftRatio)/val));
 		if (potValue >= potSteps) {
 			potValue = potSteps-1;
 		}
-		amplifierGain = 1 + potValue/(potSteps-potValue);
+		double gainDivisor = potSteps-potValue;
+		amplifierGain = 1.0 + potValue/gainDivisor + potSteps*gainShiftRatio/gainDivisor;
 		//correct the stored gain value to the actual set value
 
 		gainPot->write(potValue);
@@ -123,10 +125,19 @@ void gainLoad() {
 	else
 		amplifierGain = storage.readString().toFloat();
 	storage.close();
+
+	storage = LittleFS.open("/config/rPotRatio", "r");
+	if (storage)
+		gainShiftRatio = storage.readString().toFloat();
+	storage.close();
 }
 
 void gainSave() {
 	File storage = LittleFS.open("/config/gain", "w");
 	storage.printf("%.3f\n", amplifierGain);
 	storage.close();
+
+	storage = LittleFS.open("/config/rPotRatio", "w");
+	storage.printf("%f\n", gainShiftRatio);
+	storage.close();
 }

geoscope/ADCModule.h

@@ -17,6 +17,7 @@
 #define ADC_HOLD_TIME_CYCLES 8 //from MCP3201 datasheet: t_SUCS >= 100ns
 
 extern MCP41xxx* gainPot;
+extern double gainShiftRatio;
 
 void adcSetup();
 void adcPoll();

geoscope/MQTTService.cpp

@@ -61,7 +61,7 @@ void mqttSetup() {
 		mqttConnect();
 	}
 	gainLoad();
-	mqttNotify("Current gain: " + String(amplifierGain));
+	mqttNotify("Current gain: " + String(amplifierGain, 3));
 }
 
 void mqttShutdown() {
@@ -71,12 +71,6 @@ void mqttShutdown() {
 }
 
 void mqttConnect() {
-	if (MQTT_BROKER_TIMEOUT && attemptTimeout && millis() > *attemptTimeout) {
-		//initiates self reset if we're requiring Broker for operation (can be turned off during testing),
-		// 	and there's a set attemptTimeout
-		mqttNotify("Device Self Reset");
-		forceReset();
-	}
 	// Attempt to connect
 	mqttclient.disconnect();
 	if (mqttclient.connect(("GEOSCOPE-" + clientId).c_str()))
@@ -88,9 +82,11 @@ void mqttConnect() {
 		mqttclient.subscribe("geoscope/restart",LWMQTT_QOS1);
 		mqttclient.subscribe(CONFIG_TOPIC_PREFIX + "#", LWMQTT_QOS1);
 	}
-	else
-	{
-		minYield(20);
+	else if (MQTT_BROKER_TIMEOUT && attemptTimeout && millis() > *attemptTimeout) {
+		//initiates self reset if we're requiring Broker for operation (can be turned off during testing),
+		// 	and there's a set attemptTimeout
+		mqttNotify("Device Self Reset");
+		forceReset();
 	}
 }
 
@@ -119,7 +115,7 @@ void mqttSend() {
 			payload += String(rawBuffer[buffer_row][i]) + ",";
 		}
 		payload.remove(payload.length()-1); //trash that last ','
-		payload += "],\"gain\":" + String(amplifierGain) + "}";
+		payload += "],\"gain\":" + String(amplifierGain, 3) + "}";
 
 		if (!mqttclient.connected()) {
 			if (!attemptTimeout)
@@ -145,9 +141,8 @@ void mqttOnMessage(String & topic, String & in_payload) {
 	}
 	else if (topic.equalsIgnoreCase("geoscope/restart")) {
 		samplingDisable();
-		mqttNotify("Restart");
-		mqttclient.clearWill();
-		minYield(10);
+		mqttNotify("MQTT Initiated Restart");
+		mqttShutdown();
 		forceReset();
 	}
 	else if (topic.equalsIgnoreCase("geoscope/hb")) {

geoscope/cli.cpp

@@ -393,6 +393,21 @@ bool adc_gain(Commander &cmd) {
 
 }
 
+bool adc_ratio(Commander &cmd) {
+	float payload;
+	if (cmd.getFloat(payload)) {
+		gainShiftRatio = payload;
+		changeAmplifierGain(amplifierGain);
+		mqttReportGain(amplifierGain);
+	}
+	else {
+		cmd.rewind();
+		cmd.print(F("Gain Shift Ratio (R16/R_pot): "));
+		cmd.printf("%f\n", gainShiftRatio);
+	}
+	return 0;
+}
+
 bool adc_dump(Commander &cmd) {
 	cmd.println(F("Dumping Raw Data to Terminal. Press any key to stop."));
 	minYield(2000); //wait a couple seconds for the user to read the info
@@ -401,7 +416,11 @@ bool adc_dump(Commander &cmd) {
 }
 
 const commandList_t adcCommands[] = {
-	{"gain", adc_gain, "Get/Set Amplifier gain (min. 1, max ~834, rounds to nearest valid value)"},
+	{"gain", adc_gain, "Get/Set Amplifier gain (min. 1, max >80, rounds to nearest valid value)"},
+	{"ratio", adc_ratio, "Get/Set Amplifier gain shifting ration (R16/R_pot)"},
+	{"shift", adc_ratio, "Alias for `ratio`"},
+	{"resistor", adc_ratio, "Alias for `ratio`"},
+	{"res", adc_ratio, "Alias for `ratio`"},
 	{"dump", adc_dump, "Start streaming raw ADC data"},
 	{"exit", sub_exit, "Return to main prompt"}
 };

platformio.ini

@@ -15,7 +15,7 @@ framework = arduino
 lib_deps =
 	256dpi/MQTT
 	Commander
-	TelnetStream
+	https://github.com/jandrassy/TelnetStream
 	ESPWebDAV
 	ESP8266WebServer
 	https://github.com/akaJes/AsyncPing