Improved MeasureVoltageAndResistance and other files and examples

Author: ArminJo

.github/workflows/LibraryBuild.yml

@@ -41,7 +41,7 @@ jobs:
         #############################################################################################################
         arduino-boards-fqbn:
           - arduino:avr:uno
-          - ATTinyCore:avr:attinyx5:chip=85,clock=1internal
+#          - ATTinyCore:avr:attinyx5:chip=85,clock=1internal
 
         # Specify parameters for each board.
         # With sketches-exclude you may exclude specific examples for a board. Use a comma separated list.
@@ -50,9 +50,9 @@ jobs:
           - arduino-boards-fqbn: arduino:avr:uno
             sketches-exclude: 50Hz # Comma separated list of example names to exclude in build
 
-          - arduino-boards-fqbn: ATTinyCore:avr:attinyx5:chip=85,clock=1internal
-            platform-url: http://drazzy.com/package_drazzy.com_index.json
-            sketches-exclude: TraceTest,InterruptsTimings,EMAFilterTest,AVRUtilsDemo  # Comma separated list of example names to exclude in build
+#          - arduino-boards-fqbn: ATTinyCore:avr:attinyx5:chip=85,clock=1internal
+#            platform-url: http://drazzy.com/package_drazzy.com_index.json
+#            sketches-exclude: TraceTest,InterruptsTimings,EMAFilterTest,AVRUtilsDemo  # Comma separated list of example names to exclude in build
 
       # Do not cancel all jobs / architectures if one job fails
       fail-fast: false

Optiboot_8_1/0_Burn_avrdude-optiboot_P81_to_328P.cmd

@@ -3,5 +3,5 @@ rem unlock bootloader 0x3x No restrictions for SPM or LPM accessing the boot loa
 rem lfuse 0xFF is low power crystal 8 to 16 Mhz, 0xF7 is full swing crystal. Both with slowly rising power.
 avrdude -v -patmega328p -cstk500v1 -PCOM6 -b19200 -e -Ulock:w:0x3F:m -Uefuse:w:0xFD:m -Uhfuse:w:0xDE:m -Ulfuse:w:0xFF:m
 rem lock bootloader against overwriting, but allow reading for do_spm() feature with: lock=0x2x. No access to bootloader with 0x0x.
-avrdude -v -patmega328p -cstk500v1 -PCOM6 -b19200 -u -Uflash:w:optiboot_atmega328P_81.hex:a -Ulock:w:0x0F:m
+avrdude -v -patmega328p -cstk500v1 -PCOM6 -b19200 -Uflash:w:optiboot_atmega328P_81.hex:a -Ulock:w:0x0F:m
 pause

Optiboot_8_1/avrdude.conf

@@ -36,7 +36,7 @@ Not yet available as Arduino library.
 * [SimpleEMAFilters](https://github.com/ArminJo/Arduino-Utils?tab=readme-ov-file#simpleemafilters)
 * [ADCUtils](https://github.com/ArminJo/Arduino-Utils?tab=readme-ov-file#adcutils)
 * [HCSR04](https://github.com/ArminJo/Arduino-Utils?tab=readme-ov-file#hcsr04)
-* [MeasureVoltageAndResistance](https://github.com/ArminJo/Arduino-Utils?tab=readme-ov-file#measurevoltageandresistancehpp)
+* [MeasureVoltageAndResistance](https://github.com/ArminJo/Arduino-Utils?tab=readme-ov-file#measurevoltageandresistance)
 * [BlinkLed](https://github.com/ArminJo/Arduino-Utils?tab=readme-ov-file#blinkled)
 * [ShowInfo](https://github.com/ArminJo/Arduino-Utils?tab=readme-ov-file#showinfo)
 * [HexDump](https://github.com/ArminJo/Arduino-Utils?tab=readme-ov-file#hexdump)

Optiboot_8_1/avrdude.exe

@@ -57,6 +57,9 @@
 
 #if defined(CODE_FOR_ATTINY)
 #include "ATtinySerialOut.hpp" // Available as Arduino library "ATtinySerialOut"
+
+#define SIZE_OF_DUMMY_ARRAY     0x100    // small heap is available
+
 #define LED_PIN  PB1
 // Pin 1 has an LED connected on my Digispark board.
 #  if (LED_PIN == TX_PIN)
@@ -68,10 +71,10 @@
 //#define SIZE_OF_DUMMY_ARRAY     1800    // Stack runs into data
 //#define SIZE_OF_DUMMY_ARRAY     1700    // Stack is OK, but no heap is available
 #define SIZE_OF_DUMMY_ARRAY     0x600    // 1536 Stack is OK, and small heap is available
-uint8_t sDummyArray[SIZE_OF_DUMMY_ARRAY] __attribute__((section(".noinit"))); // Place it at end of BSS to be first overwritten by stack.
 
 #define LED_PIN  LED_BUILTIN
 #endif
+uint8_t sDummyArray[SIZE_OF_DUMMY_ARRAY] __attribute__((section(".noinit"))); // Place it at end of BSS to be first overwritten by stack.
 
 uint8_t sMCUSRStored; // content of MCUSR register at startup
 
@@ -185,6 +188,7 @@ void setup() {
 
     Serial.println();
 
+#if !defined(CODE_FOR_ATTINY)
     printRAMInfo(&Serial);
     printStackMaxUsedAndUnusedSizes(&Serial);
 
@@ -202,12 +206,13 @@ void setup() {
     printBaseRAMData(&Serial);
     printRAMInfo(&Serial);
     printStackMaxUsedAndUnusedSizes(&Serial); // test this function, it works different from function used in printRAMInfo
+#endif
 
     Serial.println(F("Dump current stack"));
     printStackDump();
 
     Serial.println(F("Show return address for current function \"setup()\""));
-    Serial.println((uint16_t)__builtin_return_address(0), HEX);
+    Serial.println((uint16_t) __builtin_return_address(0), HEX);
 
     /*
      * init sleep mode and wakeup period

README.md

@@ -5,7 +5,7 @@
  *  First voltage is measured.
  *  If voltage is zero, then resistance to ground is measured using 5 volt (VCC) and 10 kOhm or 100 kOhm supply.
  *
- *  Copyright (C) 2021  Armin Joachimsmeyer
+ *  Copyright (C) 2021-2025  Armin Joachimsmeyer
  *  Email: [email protected]
  *
  *  This file is part of Arduino-Utils https://github.com/ArminJo/Arduino-Utils.
@@ -25,43 +25,9 @@
  *
  */
 
-/*
- *  SCHEMATIC
- *            +----o A3  open/VCC (for R measurement) | open (for U measurement)
- *            |
- *            -
- *           | |
- *           | | R3 (10 kOhm)
- *           | |
- *            -
- *            |     _____
- * Input <----+----|_____|---o  A1 input (for R measurement) | open (for U measurement)
- *   ^        |     100 k - just to protect the pin
- *   |        -
- *   |       | |
- *   |       | | R1 (100 kOhm)
- *   |       | |
- *   -        -
- *  | |       |
- *  | | Rx    +---o A0  VCC(R) | input(U)
- *  | |       |
- *   -        -
- *   |       | |
- *   o GND   | | R2 (22k)
- *           | |
- *            -
- *            |
- *            +---o A2  open(R) | GND(U)
- *
- *  The ratio of R1 to Rx is equal the Ratio of (1023 - x) to x
- *
- *  => The formula is: Rx/R1 = x / (1023-x)
- *      Rx = R1 * x / (1023-x)
- *
- */
 #include <Arduino.h>
 
-#define VERSION_EXAMPLE "1.2"
+#define VERSION_EXAMPLE "2.0"
 
 //#define NO_PRINT_OF_RESISTOR_MEASURMENT_VOLTAGE
 
@@ -80,16 +46,10 @@
  * Imports and definitions for LCD
  */
 #if defined(USE_SERIAL_LCD)
-#  if defined(USE_SOFT_I2C_MASTER) // Must be declared globally. Saves 440 bytes
-#define I2C_HARDWARE 1 // use I2C Hardware
-#define I2C_PULLUP 1
-#define I2C_FASTMODE 1
-#include "SoftI2CMaster.h"
-#  endif
-#include <LiquidCrystal_I2C.h> // Use an up to date library version which has the init method
+#include "LiquidCrystal_I2C.hpp" // Here we use an enhanced version, which supports SoftI2CMaster
 #endif
 #if defined(USE_PARALLEL_LCD)
-#include <LiquidCrystal.h>
+#include "LiquidCrystal.h"
 #endif
 
 #if defined(USE_1602_LCD)
@@ -117,7 +77,9 @@ LiquidCrystal_I2C myLCD(0x27, LCD_COLUMNS, LCD_ROWS);  // set the LCD address to
 LiquidCrystal myLCD(4, 5, 6, 7, 8, 9);
 #endif
 
-// Include it after LCD settings, it requires the macros USE_LCD and USE_2004_LCD to be set
+// Include it after LCD settings, it requires the macros below and the macros USE_LCD and USE_2004_LCD to be set
+#define PRINT_OF_RESISTOR_MEASURMENT_VOLTAGE
+#define PRINT_OF_VCC
 #include "MeasureVoltageAndResistance.hpp"
 
 #define STR_HELPER(x) #x
@@ -137,10 +99,8 @@ void setup() {
     // Just to know which program is running on my Arduino
     Serial.println(F("START " __FILE__ "\r\nVersion " VERSION_EXAMPLE " from " __DATE__));
 
-    printVoltageAndResistanceUsage();
-
     /*
-     * LCD initialization
+     * LCD initialization, which may reduce VCC
      */
 #if defined(USE_SERIAL_LCD)
     myLCD.init();
@@ -151,11 +111,14 @@ void setup() {
     myLCD.begin(LCD_COLUMNS, LCD_ROWS);
 #endif
 
+    printVoltageAndResistanceUsage();
+
 #if defined(USE_SERIAL_LCD) || defined(USE_PARALLEL_LCD)
     myLCD.print(F("Volt+Ohm meter"));
     myLCD.setCursor(0, 1);
     myLCD.print(F(VERSION_EXAMPLE " " __DATE__));
     delay(2000);
+    myLCD.clear();
 #endif
 
 }

examples/AVRUtilsDemo/AVRUtilsDemo.ino

@@ -31,6 +31,7 @@
 
 // External Reference Current is 150 uA for 5 V and 100 uA for 3.5 V
 #define READING_FOR_AREF 1024L // Datasheet 24.2: The minimum value represents GND and the maximum value represents the voltage on the AREF pin minus 1 LSB
+#define MAX_ADC_VALUE    1023L
 
 // PRESCALE4 => 13 * 4 = 52 microseconds per ADC conversion at 1 MHz Clock => 19,2 kHz
 #define ADC_PRESCALE2    1 // 26 microseconds per ADC conversion at 1 MHz
@@ -172,8 +173,10 @@
 extern long sLastVCCCheckMillis;
 extern uint8_t sVCCTooLowCounter;
 
+uint16_t readADCChannel();
 uint16_t readADCChannel(uint8_t aADCChannelNumber);
 uint16_t readADCChannelWithReference(uint8_t aADCChannelNumber, uint8_t aReference);
+uint16_t readADCChannelWithReferenceUsingInternalReference(uint8_t aADCChannelNumber);
 uint16_t waitAndReadADCChannelWithReference(uint8_t aADCChannelNumber, uint8_t aReference);
 uint16_t waitAndReadADCChannelWithReferenceAndRestoreADMUXAndReference(uint8_t aADCChannelNumber, uint8_t aReference);
 uint16_t readADCChannelWithOversample(uint8_t aADCChannelNumber, uint8_t aOversampleExponent);
@@ -188,6 +191,8 @@ uint16_t readADCChannelWithReferenceMaxMicros(uint8_t aADCChannelNumber, uint8_t
 uint16_t readUntil4ConsecutiveValuesAreEqual(uint8_t aADCChannelNumber, uint8_t aReference, uint8_t aDelay,
         uint8_t aAllowedDifference, uint8_t aMaxRetries);
 
+void setADCChannelForNextConversionAndWaitUsingInternalReference(uint8_t aADCChannelNumber);
+void setADCChannelForNextConversionAndWaitUsingDefaultReference(uint8_t aADCChannelNumber);
 uint8_t checkAndWaitForReferenceAndChannelToSwitch(uint8_t aADCChannelNumber, uint8_t aReference);
 
 /*

examples/VoltAndOhmmeter/VoltAndOhmmeter.ino

@@ -27,6 +27,7 @@
 
 #include "ADCUtils.h"
 #if defined(ADC_UTILS_ARE_AVAILABLE) // set in ADCUtils.h, if supported architecture was detected
+#define ADC_UTILS_ARE_INCLUDED
 
 #if !defined(STR)
 #define STR_HELPER(x) #x
@@ -41,7 +42,7 @@
  * with INTERNAL you can calibrate your ADC readout. For my Nanos I measured e.g. 1060 mV and 1093 mV.
  */
 #if !defined(ADC_INTERNAL_REFERENCE_MILLIVOLT)
-#define ADC_INTERNAL_REFERENCE_MILLIVOLT    1100L // Change to value measured at the AREF pin. If value > real AREF voltage, measured values are > real values
+#define ADC_INTERNAL_REFERENCE_MILLIVOLT    1100UL // Change to value measured at the AREF pin. If value > real AREF voltage, measured values are > real values
 #endif
 
 // Union to speed up the combination of low and high bytes to a word
@@ -66,6 +67,11 @@ union WordUnionForADCUtils {
 #else
 //#define LOCAL_DEBUG // This enables debug output only for this file
 #endif
+#if defined(INFO)
+#define LOCAL_INFO
+#else
+//#define LOCAL_INFO // This enables debug output only for this file
+#endif
 
 /*
  * Persistent storage for VCC value
@@ -79,6 +85,27 @@ uint8_t sVCCTooLowCounter = 0;
 
 /*
  * Conversion time is defined as 0.104 milliseconds by ADC_PRESCALE in ADCUtils.h.
+ * Use previous settings
+ */
+uint16_t readADCChannel() {
+    WordUnionForADCUtils tUValue;
+
+    // ADCSRB = 0; // Only active if ADATE is set to 1.
+    // ADSC-StartConversion ADIF-Reset Interrupt Flag - NOT free running mode
+    ADCSRA = (_BV(ADEN) | _BV(ADSC) | _BV(ADIF) | ADC_PRESCALE);
+
+    // wait for single conversion to finish
+    loop_until_bit_is_clear(ADCSRA, ADSC);
+
+    // Get value
+    tUValue.UByte.LowByte = ADCL;
+    tUValue.UByte.HighByte = ADCH;
+    return tUValue.UWord;
+    //    return ADCL | (ADCH <<8); // needs 4 bytes more
+}
+
+/*
+ * Use new channel aADCChannelNumber, but do not wait for channel switching
  */
 uint16_t readADCChannel(uint8_t aADCChannelNumber) {
     WordUnionForADCUtils tUValue;
@@ -97,7 +124,6 @@ uint16_t readADCChannel(uint8_t aADCChannelNumber) {
     return tUValue.UWord;
     //    return ADCL | (ADCH <<8); // needs 4 bytes more
 }
-
 /*
  * Conversion time is defined as 0.104 milliseconds by ADC_PRESCALE in ADCUtils.h.
  */
@@ -118,6 +144,22 @@ uint16_t readADCChannelWithReference(uint8_t aADCChannelNumber, uint8_t aReferen
     return tUValue.UWord;
 }
 
+uint16_t readADCChannelWithReferenceUsingInternalReference(uint8_t aADCChannelNumber) {
+    WordUnionForADCUtils tUValue;
+    ADMUX = aADCChannelNumber | (INTERNAL << SHIFT_VALUE_FOR_REFERENCE);
+
+    // ADCSRB = 0; // Only active if ADATE is set to 1.
+    // ADSC-StartConversion ADIF-Reset Interrupt Flag - NOT free running mode
+    ADCSRA = (_BV(ADEN) | _BV(ADSC) | _BV(ADIF) | ADC_PRESCALE);
+
+    // wait for single conversion to finish
+    loop_until_bit_is_clear(ADCSRA, ADSC);
+
+    // Get value
+    tUValue.UByte.LowByte = ADCL;
+    tUValue.UByte.HighByte = ADCH;
+    return tUValue.UWord;
+}
 /*
  * Conversion time is defined as 0.104 milliseconds by ADC_PRESCALE in ADCUtils.h.
  * Does NOT restore ADMUX after reading
@@ -145,6 +187,19 @@ void setADCChannelAndReferenceForNextConversion(uint8_t aADCChannelNumber, uint8
     ADMUX = aADCChannelNumber | (aReference << SHIFT_VALUE_FOR_REFERENCE);
 }
 
+/*
+ * 100 kOhm requires < 100 us, 1 MOhm requires 120 us S&H switching time
+ */
+void setADCChannelForNextConversionAndWaitUsingInternalReference(uint8_t aADCChannelNumber) {
+    ADMUX = aADCChannelNumber | (INTERNAL << SHIFT_VALUE_FOR_REFERENCE);
+    delayMicroseconds(120); // experimental value is <= 1100 us for Nano board
+}
+
+void setADCChannelForNextConversionAndWaitUsingDefaultReference(uint8_t aADCChannelNumber) {
+    ADMUX = aADCChannelNumber | (DEFAULT << SHIFT_VALUE_FOR_REFERENCE);
+    delayMicroseconds(120); // experimental value is <= 1100 us for Nano board
+}
+
 /*
  * @return original ADMUX register content for optional later restoring values
  * All experimental values are acquired by using the ADCSwitchingTest example from this library
@@ -639,13 +694,13 @@ bool isVCCUSBPowered(Print *aSerial) {
 }
 
 /*
+ * It checks every 10 seconds for 6 times, and then returns true if the undervoltage condition ( <3.4V ) still applies.
  * @ return true only once, when VCC_UNDERVOLTAGE_CHECKS_BEFORE_STOP (6) times voltage too low -> shutdown
  */
 bool isVCCUndervoltageMultipleTimes() {
     /*
      * Check VCC every VCC_CHECK_PERIOD_MILLIS (10) seconds
      */
-
     if (millis() - sLastVCCCheckMillis >= VCC_CHECK_PERIOD_MILLIS) {
         sLastVCCCheckMillis = millis();
 
@@ -655,30 +710,32 @@ bool isVCCUndervoltageMultipleTimes() {
         readVCCVoltageMillivolt();
 #  endif
 
-        if (sVCCTooLowCounter < VCC_UNDERVOLTAGE_CHECKS_BEFORE_STOP) {
-            /*
-             * Do not check again if shutdown has happened
-             */
+        /*
+         * Do not check again if shutdown signaling (sVCCTooLowCounter >= 6) has happened
+         */
+        if (sVCCTooLowCounter < VCC_UNDERVOLTAGE_CHECKS_BEFORE_STOP) { // VCC_UNDERVOLTAGE_CHECKS_BEFORE_STOP = 6
             if (sVCCVoltageMillivolt > VCC_UNDERVOLTAGE_THRESHOLD_MILLIVOLT) {
                 sVCCTooLowCounter = 0; // reset counter
             } else {
                 /*
-                 * Voltage too low, wait VCC_UNDERVOLTAGE_CHECKS_BEFORE_STOP (6) times and then shut down.
+                 * Voltage too low, wait VCC_UNDERVOLTAGE_CHECKS_BEFORE_STOP (6) times and then signal shut down.
                  */
                 if (sVCCVoltageMillivolt < VCC_EMERGENCY_UNDERVOLTAGE_THRESHOLD_MILLIVOLT) {
                     // emergency shutdown
                     sVCCTooLowCounter = VCC_UNDERVOLTAGE_CHECKS_BEFORE_STOP;
-#  if defined(INFO)
+#  if defined(LOCAL_INFO)
                     Serial.println(
                             F(
-                                    "Voltage < " STR(VCC_EMERGENCY_UNDERVOLTAGE_THRESHOLD_MILLIVOLT) " mV detected -> emergency shutdown"));
+                                    "Undervoltage < " STR(VCC_EMERGENCY_UNDERVOLTAGE_THRESHOLD_MILLIVOLT) " mV detected -> emergency shutdown"));
 #  endif
                 } else {
                     sVCCTooLowCounter++;
-#  if defined(INFO)
-                    Serial.print(F("Voltage < " STR(VCC_UNDERVOLTAGE_THRESHOLD_MILLIVOLT) " mV detected: "));
+#  if defined(LOCAL_INFO)
+                    Serial.print(sVCCVoltageMillivolt);
+                    Serial.print(F(" mV < " STR(VCC_UNDERVOLTAGE_THRESHOLD_MILLIVOLT) " mV undervoltage detected: "));
+
                     Serial.print(VCC_UNDERVOLTAGE_CHECKS_BEFORE_STOP - sVCCTooLowCounter);
-                    Serial.println(F(" tries left"));
+                    Serial.println(F(" attempts left"));
 #  endif
                 }
                 if (sVCCTooLowCounter == VCC_UNDERVOLTAGE_CHECKS_BEFORE_STOP) {
@@ -820,4 +877,7 @@ float getVCCVoltage() {
 #if defined(LOCAL_DEBUG)
 #undef LOCAL_DEBUG
 #endif
+#if defined(LOCAL_INFO)
+#undef LOCAL_INFO
+#endif
 #endif // _ADC_UTILS_HPP