init commit

.gitignore

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+*.eep
+*.hex
+*.lss
+*.map
+/firmware/dep/*

README.md

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+## Arduino Uno Transistor Tester
+
+This project is inspired by [ArduTester V1.13: The Arduino UNO Transistor Tester](https://www.hackster.io/plouc68000/ardutester-v1-13-the-arduino-uno-transistor-tester-dbafb4), in fact, hardware is the same and schematic is almost identical.
+
+### Why?
+
+I assembled tester using instruction from original project[^1], flashed firmware that author attached, but tester did not work very well. Measured capacity was pretty accurate, but ESR does not seem to be ok. ESR was 0 Ohms on all capacitors above ~100 uf, and 20-40 Ohms on all capacitors below 100 uf. Tester stuck when I measured inductors and resistors. It reboots itself when measuring diodes. So I configured latest firmware by Markus Reschke, flashed it and all glitches mentioned above are gone.
+
+### Hardware:
+
+- Arduino Uno R3
+- 1602 LCD (HD44780)
+- Push button
+- Resistors:
+  - 1k Ohm x1
+  - 10k Ohm x1
+  - 470K Ohm x3
+  - 680 Ohm x3
+
+### Firmware
+
+I took **Markus Reschke firmware version 1.45m**[^2] and configured `config.h`, `config_328.h` and `Makefile`.
+
+Enabled functions:
+
+- PWM generator
+- Inductance measurement
+- ESR measurement
+- check for optocouplers
+- check for Unijunction Transistor
+- check for Schottky Transistor (Schottky-clamped BJT)
+
+Feel free to configure firmware, all instructions are available in original README and in configuration files.
+
+### Diagram
+
+The only difference in schematic I made is I moved button from A3 pin to D1, because in documentation it says: `"can't be same port as ADC_PORT or R_PORT"`, so I moved button to `PORTD`[^3].
+![diagram](/resources/board.png)
+
+### Scheme
+
+![scheme](/resources/scheme.png)
+
+### Links
+
+[^1]: [ArduTester V1.13: The Arduino UNO Transistor Tester](https://www.hackster.io/plouc68000/ardutester-v1-13-the-arduino-uno-transistor-tester-dbafb4)
+[^2]: [Firmware by Markus Reschke version 1.45m](https://github.com/Mikrocontroller-net/transistortester/blob/master/Software/Markus/ComponentTester-1.45m.tgz)
+[^3]: [Arduino Uno Pinout Diagram](https://images.prismic.io/circuito/8e3a980f0f964cc539b4cbbba2654bb660db6f52_arduino-uno-pinout-diagram.png?auto=compress,format)

firmware/ADC.c

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+/* ************************************************************************
+ *
+ *   ADC functions
+ *
+ *   (c) 2012-2020 by Markus Reschke
+ *   based on code from Markus Frejek and Karl-Heinz Kübbeler
+ *
+ * ************************************************************************ */
+
+
+/*
+ *  local constants
+ */
+
+/* source management */
+#define ADC_C
+
+
+/*
+ *  include header files
+ */
+
+/* local includes */
+#include "config.h"           /* global configuration */
+#include "common.h"           /* common header file */
+#include "variables.h"        /* global variables */
+#include "functions.h"        /* external functions */
+
+
+/* ************************************************************************
+ *   ADC
+ * ************************************************************************ */
+
+
+/*
+ *  read ADC channel and return voltage in mV
+ *  - use Vcc as reference by default
+ *  - switch to bandgap reference for low voltages (< 1.0V) to improve
+ *    ADC resolution
+ *  - with a 125kHz ADC clock a single conversion needs about 0.1ms
+ *    with 25 samples we end up with about 2.6ms
+ *
+ *  requires:
+ *  - Channel: ADC MUX input channel
+ *    - ATmega328: register bits corresponding with MUX0-3
+ *    - ATmega324/644/1284: register bits corresponding with MUX0-4
+ *    - ATmega640/1280/2560: register bits corresponding with MUX0-4
+ *      (todo: add MUX5 to support also ADC8-15)
+ */
+
+uint16_t ReadU(uint8_t Channel)
+{
+  uint16_t          U;             /* return value (mV) */
+  uint8_t           Counter;       /* loop counter */
+  uint8_t           Ref;           /* voltage reference register bits */
+  uint32_t          Value;         /* ADC value */
+
+  /* AREF pin is connected to external buffer cap (1nF) */
+
+  #if 0
+  /* manage channels ADC8-15 (ATmega640/1280/2560) */
+  if (Channel & 0b00100000)        /* bit 6 set: ADC8-15 */
+  {
+    ADCSRB |= (1 << MUX5);         /* set MUX5 */
+  }
+  else                             /* bit 6 not set: ADC0-7 */
+  {
+    ADCSRB &= ~(1 << MUX5);        /* clear MUX5 */
+  }
+  #endif
+
+  /* prepare bitfield for register: start with AVcc as voltage reference */
+  Channel &= ADC_CHAN_MASK;        /* filter reg bits for MUX channel */
+  Channel |= ADC_REF_VCC;          /* add bits for voltage reference: AVcc */
+
+sample:
+
+  ADMUX = Channel;                 /* set input channel and U reference */
+
+  /*
+   *  change of voltage reference
+   *  - voltage needs some time to stabilize at buffer cap 
+   *  - run a dummy conversion after change (recommended by datasheet)
+   *  - It seems that we have to run a dummy conversion also after the
+   *    ADC hasn't run for a while. So let's do one anyway.
+   */
+
+  Ref = Channel & ADC_REF_MASK;    /* get register bits for voltage reference */
+  if (Ref != Cfg.Ref)              /* reference source has changed */
+  {
+    /* wait some time for voltage stabilization */
+    #ifndef ADC_LARGE_BUFFER_CAP
+      /* buffer cap: 1nF or none at all */
+      wait100us();                   /* 100µs */
+    #else
+      /* buffer cap: 100nF */
+      wait10ms();                    /* 10ms */
+    #endif
+
+    #if 0
+    /* dummy conversion */
+    ADCSRA |= (1 << ADSC);         /* start conversion */
+    while (ADCSRA & (1 << ADSC));  /* wait until conversion is done */
+    #endif
+
+    Cfg.Ref = Ref;                 /* update reference source */
+  }
+
+  /* perform dummy conversion anyway */
+  ADCSRA |= (1 << ADSC);         /* start conversion */
+  while (ADCSRA & (1 << ADSC));  /* wait until conversion is done */
+
+
+  /*
+   *  sample ADC readings
+   */
+
+  Value = 0UL;                     /* reset sampling variable */
+  Counter = 0;                     /* reset counter */
+
+  while (Counter < Cfg.Samples)    /* take samples */
+  {
+    ADCSRA |= (1 << ADSC);         /* start conversion */
+    while (ADCSRA & (1 << ADSC));  /* wait until conversion is done */
+
+    Value += ADCW;                 /* add ADC reading */
+
+    /* auto-switch voltage reference for low readings */
+    if (Counter == 4)                   /* 5 samples */
+    {
+      if ((uint16_t)Value < 1024)       /* < 1V (5V / 5 samples) */
+      {
+        if (Ref != ADC_REF_BANDGAP)     /* bandgap ref not selected */
+        {
+          if (Cfg.AutoScale == 1)       /* autoscaling enabled */
+          {
+            Channel &= ~ADC_REF_MASK;     /* clear reference bits */
+            Channel |= ADC_REF_BANDGAP;   /* select bandgap reference */
+
+            goto sample;                /* re-run sampling */
+          }
+        }
+      }
+    }
+
+    Counter++;                     /* another sample done */
+  }
+
+
+  /*
+   *  convert ADC reading to voltage
+   *  - single sample: U = ADC reading * U_ref / 1024
+   */
+
+  /* get voltage of reference used */
+  if (Ref == ADC_REF_BANDGAP)      /* bandgap reference */
+  {
+    U = Cfg.Bandgap;                 /* voltage of bandgap reference */
+  }
+  else                             /* Vcc as reference */
+  {
+    U = Cfg.Vcc;                     /* voltage of Vcc */   
+  }
+
+  /* convert to voltage; */
+  Value *= U;                      /* ADC readings * U_ref */
+//  Value += 511 * Cfg.Samples;      /* automagic rounding */
+  Value /= 1024;                   /* / 1024 for 10bit ADC */
+
+  /* de-sample to get average voltage */
+  Value /= Cfg.Samples;
+  U = (uint16_t)Value;
+
+  return U; 
+}
+
+
+
+/* ************************************************************************
+ *   convenience functions
+ * ************************************************************************ */
+
+
+/*
+ *  wait 5ms and then read ADC
+ *  - same as ReadU()
+ */
+
+uint16_t ReadU_5ms(uint8_t Channel)
+{
+   wait5ms();       /* wait 5ms */
+
+   return (ReadU(Channel));
+}
+
+
+
+/*
+ *  wait 20ms and then read ADC
+ *  - same as ReadU()
+ */
+
+uint16_t ReadU_20ms(uint8_t Channel)
+{
+  wait20ms();       /* wait 20ms */
+
+  return (ReadU(Channel));
+}
+
+
+
+/* ************************************************************************
+ *   clean-up of local constants
+ * ************************************************************************ */
+
+
+/* source management */
+#undef ADC_C
+
+
+
+/* ************************************************************************
+ *   EOF
+ * ************************************************************************ */