--- /dev/null
+SUBDIRS = src doc
--- /dev/null
+# -*- Autoconf -*-
+# Process this file with autoconf to produce a configure script.
+
+AC_PREREQ([2.69])
+AC_INIT([sensors], [0.1], [arjen@andromeda.nl])
+AM_INIT_AUTOMAKE([-Wall foreign])
+AC_CONFIG_SRCDIR([src/Cmeter.cpp])
+AC_CONFIG_HEADERS([config.h])
+
+# Checks for programs.
+AC_PROG_CXX
+AC_PROG_CC
+
+# Check for wx-widgets
+
+AC_PATH_PROG(WX_CONFIG, wx-config, no)
+if test $WX_CONFIG = "no"
+then
+ echo "WX widgets is not installed"
+ exit 1
+fi
+
+WX_CXXFLAGS=`wx-config --cxxflags`
+CXXFLAGS="$CXXFLAGS $WX_CXXFLAGS"
+WX_LDFLAGS=`wx-config --libs`
+LDFLAGS="$LDFLAGS $WX_LDFLAGS"
+
+#Checks for libraries.
+AC_CHECK_LIB([pigpiod_if2], [pigpio_start])
+# FIXME: Replace `main' with a function in `-lrt':
+AC_CHECK_LIB([rt], [main])
+
+# Checks for header files.
+AC_CHECK_HEADERS([unistd.h])
+AC_CHECK_HEADERS([wx/wx.h])
+
+# Checks for typedefs, structures, and compiler characteristics.
+AC_CHECK_HEADER_STDBOOL
+AC_TYPE_UINT32_T
+
+# Checks for library functions.
+
+AC_CONFIG_FILES([Makefile
+ src/Makefile])
+AC_OUTPUT
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+<?xml version='1.0'?>
+<doc>
+<article>
+
+<titlepage>
+ <title>Raspberry Pi Sensors</title>
+ <author>Arjen Baart <arjen@andromeda.nl></author>
+ <date>February 18, 2021</date>
+ <abstract>
+ </abstract>
+</titlepage>
+
+<chapter>
+ <heading>Single slope voltmeter</heading>
+
+<para>
+The single slope voltmeter creates a ramp by charginf a capacitor with a contant current.
+See also <emph>The Art of Electronics, page 416</emph>.
+The figure below shows the concept:
+</para>
+
+<picture src='single-slope.svg'/>
+
+<para>
+At rest, the capacitor C1 is shorted to ground by applying a positive voltage to the gate of the MOSFET.
+The cycle starts when the gate voltage drops to 0 and capacitor C1 charges from the current source.
+The voltage rises linearly and is compared to the input voltage.
+When the voltage across C1 rises above the input voltage connected to the negative input of the comparator,
+the comparator's open collector output is drawn to ground.
+The cycle is shown in the timing diagram below:
+</para>
+
+<picture src='timing-diagram.svg'/>
+
+<para>
+The time from releasing the MOSFET to the comparator's output going low is proportianal to the input volatge:
+
+<verbatim>
+ t = C / I * Uin
+</verbatim>
+</para>
+
+<para>
+The measurable range of the input voltage is determined by the input voltage that can be handled by the comparator
+and the maximum voltage for the current source.
+For most comparators, the input voltage must be within 0.5 V to 1 V of the supply rails.
+With a supply voltage of 5V, input voltages from 1 to 4V can be measured.
+To measure input voltages from 0 to 30 V, an input devider must devide the input voltage by 10 and provide
+an offset of 1 V:
+</para>
+
+<picture src='input-divider.svg'/>
+
+<para>
+<!--
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+ <mi>R</mi>
+</mfrac>
+</math>
+-->
+
+<!--
+ <math:mrow>
+ <math:mi>U<math:msub>in</math:msub></math:mi>
+ </math:mrow>
+ <math:mrow>
+ <math:mi>R<math:msub>1</math:msub></math:mi>
+ </math:mrow>
+-->
+
+<verbatim>
+ (Uin - Uo) / R1 + (Uc - Uo) / R3 - Uo / R2 = 0
+</verbatim>
+<verbatim>
+ Uo = (Uin * R2 * R3 + Uc * R1 * R2) / (R2 * R3 + R1 * R2 + R1 * R3)
+
+ Uc = 5 V
+ R1 = 1.2 M
+ R2 = 150k
+ R3 = 560 k
+
+ Uo = Uin * 0.086 + 0.97
+</verbatim>
+</para>
+</chapter>
+<chapter>
+ <heading>Capacitance meter</heading>
+<para>
+When, instead of measuring Uin, the input voltage is fixed to Uref, the same
+circuit can be used to measure the capacitance of C1, as shown below:
+</para>
+<picture src='C-meter.svg'/>
+</chapter>
+</article>
+</doc>
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+refdes=R6
+T 51400 48300 5 10 1 1 0 0 1
+value=10k
+}
+N 41500 50300 51300 50300 4
+N 51300 50300 51300 48800 4
+N 51300 42000 51300 47900 4
+N 50900 46800 51300 46800 4
+N 42000 44700 42000 42000 4
+C 48600 46600 1 180 0 resistor-2.sym
+{
+T 48200 46250 5 10 0 0 180 0 1
+device=RESISTOR
+T 48400 46300 5 10 1 1 180 0 1
+refdes=R7
+T 47900 46000 5 10 1 1 0 0 1
+value=1.2M
+}
+C 48700 48500 1 90 0 resistor-2.sym
+{
+T 48350 48900 5 10 0 0 90 0 1
+device=RESISTOR
+T 48400 48700 5 10 1 1 90 0 1
+refdes=R6
+T 48700 48900 5 10 1 1 0 0 1
+value=560k
+}
+C 49100 45200 1 90 0 resistor-2.sym
+{
+T 48750 45600 5 10 0 0 90 0 1
+device=RESISTOR
+T 48800 45400 5 10 1 1 90 0 1
+refdes=R8
+T 48500 45200 5 10 1 1 0 0 1
+value=150k
+}
+C 49300 46100 1 270 0 capacitor-4.sym
+{
+T 50400 45900 5 10 0 0 270 0 1
+device=POLARIZED_CAPACITOR
+T 49800 45900 5 10 1 1 270 0 1
+refdes=C2
+T 50000 45900 5 10 0 0 270 0 1
+symversion=0.1
+T 49800 45400 5 10 1 1 0 0 1
+value=1uF
+}
+N 45700 43200 49500 43200 4
+N 49500 43200 49500 45200 4
+N 49000 45200 49000 43200 4
+N 49500 46100 49000 46100 4
+N 49000 46100 49000 46500 4
+N 49200 46500 48600 46500 4
+N 48600 46500 48600 48500 4
+N 47700 46500 47400 46500 4
+N 47400 46500 47400 42000 4
+N 48600 49400 48600 49800 4
+T 47200 41700 9 10 1 0 0 0 1
+Uin
+T 41800 41600 9 10 1 0 0 0 1
+Cycle
+T 51000 41700 9 10 1 0 0 0 1
+Cmp Out
--- /dev/null
+#include <iostream>
+#include <iomanip>
+#include <fstream>
+
+#include <stdio.h>
+#include <unistd.h>
+#include <pigpiod_if2.h>
+
+
+#define CYCLE_OUT 18 // The cycle output
+#define CMP_IN 17 // The signal from the comparator
+#define NR_SAMPLES 20 // Number of samples to avaerage out the jitter
+
+void gpio_callback(int pi, unsigned user_gpio, unsigned level, uint32_t tick, void * userdata);
+
+#define INPUT_OFFSET 0.97
+#define INPUT_DIVIDER 0.086
+#define SLOPE_FACTOR 38.7 // Current / Voltage ( 117uA / 3.0V)
+
+class DVM
+{
+ int pi; // Connection to pigpio daemon
+ unsigned cycle_gate; // The gate to run a measurement cycle
+ unsigned comparator; // The signal from the comparator
+
+
+ uint32_t last_tick;
+ uint32_t measure_start;
+
+ uint32_t samples[NR_SAMPLES];
+ int sample_index;
+
+ float U; // The measured voltage
+
+
+public:
+
+ void input_event(unsigned gpio, unsigned level, uint32_t tick)
+ {
+ float measure_time;
+
+ //printf("Input event: input %u = %u, %d\n", gpio, level, tick - last_tick);
+
+ if (gpio == cycle_gate && level == 1)
+ {
+ measure_start = tick;
+ }
+
+ if (gpio == comparator && level == 1)
+ {
+ samples[sample_index++] = tick - measure_start;
+ sample_index %= NR_SAMPLES;
+
+ measure_time = (float)(tick - measure_start) / 1.0e6;
+ U = measure_time * 11.4 - INPUT_OFFSET;
+ U /= INPUT_DIVIDER;
+
+ gpio_write(pi, cycle_gate, 0);
+ }
+ if (gpio == comparator && level == 0)
+ {
+ gpio_write(pi, cycle_gate, 1);
+ }
+ last_tick = tick;
+ }
+
+
+ DVM(int pi_connection, unsigned gate, unsigned cmp)
+ {
+ int open_return;
+
+ pi = pi_connection;
+ cycle_gate = gate;
+ comparator = cmp;
+
+ last_tick = 0;
+ sample_index = 0;
+
+
+ set_mode(pi, comparator, PI_INPUT);
+ set_mode(pi, cycle_gate, PI_OUTPUT);
+ set_pull_up_down(pi, comparator, PI_PUD_OFF);
+
+ open_return = callback_ex(pi, cycle_gate, EITHER_EDGE, gpio_callback, this);
+ //fprintf(stderr, "Set callback returns %d.\n", open_return);
+ open_return = callback_ex(pi, comparator, EITHER_EDGE, gpio_callback, this);
+ //fprintf(stderr, "Set callback returns %d.\n", open_return);
+ gpio_write(pi, cycle_gate, 0);
+ sleep(1);
+ gpio_write(pi, cycle_gate, 1);
+ }
+
+ float Voltage()
+ {
+ uint32_t sum = 0;
+ uint32_t average_time;
+ float measure_time;
+
+ // To filter out the jitter, calculate the average measured time
+
+ for (int i = 0; i < NR_SAMPLES; i++)
+ {
+ sum += samples[i];
+ }
+
+ average_time = (sum / NR_SAMPLES) >> 5 << 5;
+ std::cout << " Average time = " << average_time << "\n";
+ measure_time = average_time / 1.0e6;
+ U = measure_time * SLOPE_FACTOR;
+
+ return U;
+ }
+};
+
+void gpio_callback(int pi, unsigned user_gpio, unsigned level, uint32_t tick, void * userdata)
+{
+ DVM *sensor;
+
+ sensor = (DVM *)userdata;
+ sensor->input_event(user_gpio, level, tick);
+}
+
+
+int main()
+{
+ int pi;
+ std::ofstream sensorfile;
+
+ pi = pigpio_start(NULL, NULL);
+ if (pi < 0)
+ {
+ // pigpio initialisation failed.
+ fprintf(stderr, "GPIO initialization failed.\n");
+
+ }
+ else
+ {
+ // pigpio initialised okay.
+ DVM sensor(pi, CYCLE_OUT, CMP_IN);
+
+ while (true)
+ {
+ sleep(1);
+ printf("%.3f\n", sensor.Voltage());
+ fflush(stdout);
+
+ sensorfile.open("sensor1");
+ sensorfile << std::fixed << std::setprecision(3) << sensor.Voltage() << " uF\n";
+ sensorfile.close();
+ }
+ pigpio_stop(pi);
+
+ }
+
+}
+
--- /dev/null
+bin_PROGRAMS = tsic pulsewidth voltmeter Cmeter meters
+
+
+tsic_SOURCES = tsic.cpp
+pulsewidth_SOURCES = pulsewidth.cpp
+voltmeter_SOURCES = voltmeter.cpp
+Cmeter_SOURCES = Cmeter.cpp
+meters_SOURCES = meters.cpp
--- /dev/null
+#include <wx/wx.h>
+#include <wx/textfile.h>
+
+class MyApp: public wxApp
+{
+public:
+ virtual bool OnInit();
+};
+
+class MyFrame: public wxFrame
+{
+public:
+ MyFrame(const wxString& title, const wxPoint& pos, const wxSize& size);
+private:
+ void OnHello(wxCommandEvent& event);
+ void OnExit(wxCommandEvent& event);
+ void OnAbout(wxCommandEvent& event);
+ wxDECLARE_EVENT_TABLE();
+};
+
+class SensorDisplay : public wxPanel
+{
+ int sensorvalue;
+ wxTimer *timer;
+
+public:
+ SensorDisplay(wxFrame *parent);
+ void OnPaint(wxPaintEvent& event);
+ void OnTimer(wxCommandEvent& event);
+};
+
+SensorDisplay::SensorDisplay(wxFrame *parent)
+ : wxPanel(parent, -1, wxPoint(-1, -1), wxSize(-1, -1), wxBORDER_SUNKEN)
+{
+ sensorvalue = 0;
+ wxColour background(wxT("LIGHT STEEL BLUE"));
+
+ SetBackgroundColour(background);
+
+ timer = new wxTimer(this, 1);
+ this->Connect(wxEVT_PAINT, wxPaintEventHandler(SensorDisplay::OnPaint));
+ Connect(wxEVT_TIMER, wxCommandEventHandler(SensorDisplay::OnTimer));
+
+ timer->Start(500);
+}
+
+void SensorDisplay::OnPaint(wxPaintEvent& event)
+{
+ wxString displayed_value;
+
+ wxFont display_font(36, wxFONTFAMILY_MODERN,wxFONTSTYLE_NORMAL,
+ wxFONTWEIGHT_BOLD, false);
+
+ sensorvalue++;
+ displayed_value.Printf(wxT("%04d"), sensorvalue);
+
+ wxTextFile sensorfile(wxT("sensor1"));
+ sensorfile.Open();
+ displayed_value = sensorfile.GetFirstLine();
+
+ wxPaintDC dc(this);
+
+ dc.SetFont(display_font);
+
+ dc.DrawText(displayed_value, 60, 80);
+}
+
+void SensorDisplay::OnTimer(wxCommandEvent& event)
+{
+ sensorvalue += 10;
+ Refresh();
+}
+
+enum
+{
+ ID_Hello = 1
+};
+
+wxBEGIN_EVENT_TABLE(MyFrame, wxFrame)
+ EVT_MENU(ID_Hello, MyFrame::OnHello)
+ EVT_MENU(wxID_EXIT, MyFrame::OnExit)
+ EVT_MENU(wxID_ABOUT, MyFrame::OnAbout)
+wxEND_EVENT_TABLE()
+
+wxIMPLEMENT_APP(MyApp);
+
+bool MyApp::OnInit()
+{
+ MyFrame *frame = new MyFrame( "Sensors", wxPoint(50, 50), wxSize(450, 340) );
+ frame->Show( true );
+ return true;
+}
+
+MyFrame::MyFrame(const wxString& title, const wxPoint& pos, const wxSize& size)
+ : wxFrame(NULL, wxID_ANY, title, pos, size)
+{
+ wxMenu *menuFile = new wxMenu;
+ menuFile->Append(ID_Hello, "&Hello...\tCtrl-H",
+ "Help string shown in status bar for this menu item");
+ menuFile->AppendSeparator();
+ menuFile->Append(wxID_EXIT);
+ wxMenu *menuHelp = new wxMenu;
+ menuHelp->Append(wxID_ABOUT);
+ wxMenuBar *menuBar = new wxMenuBar;
+ menuBar->Append( menuFile, "&File" );
+ menuBar->Append( menuHelp, "&Help" );
+ SetMenuBar( menuBar );
+
+ SensorDisplay *display = new SensorDisplay(this);
+
+ CreateStatusBar();
+ SetStatusText( "Raspberry Pi sensors" );
+}
+
+void MyFrame::OnExit(wxCommandEvent& event)
+{
+ Close( true );
+}
+
+void MyFrame::OnAbout(wxCommandEvent& event)
+{
+ wxMessageBox( "Raspberry Pi sensor display version 1.0",
+ "About Sensors...", wxOK | wxICON_INFORMATION );
+}
+
+void MyFrame::OnHello(wxCommandEvent& event)
+{
+ wxLogMessage("Hello from sensors!");
+}
+
--- /dev/null
+#include <iostream>
+#include <iomanip>
+#include <fstream>
+
+#include <stdio.h>
+#include <unistd.h>
+#include <pigpiod_if2.h>
+
+
+#define CMP_IN 22 // The signal from the comparator
+#define NR_SAMPLES 20
+
+void gpio_callback(int pi, unsigned user_gpio, unsigned level, uint32_t tick, void * userdata);
+
+
+class DVM
+{
+ int pi; // Connection to pigpio daemon
+ unsigned comparator; // The signal from the comparator
+
+
+ uint32_t last_tick;
+ uint32_t measure_start;
+
+ uint32_t samples[NR_SAMPLES];
+ int sample_index;
+
+public:
+
+ void input_event(unsigned gpio, unsigned level, uint32_t tick)
+ {
+ //printf("Input event: input %u = %u, %d\n", gpio, level, tick - last_tick);
+
+
+ if (gpio == comparator && level == 1)
+ {
+ measure_start = tick;
+ }
+ if (gpio == comparator && level == 0)
+ {
+ samples[sample_index] = tick - measure_start;
+ //printf(" Measured time = %d\n", tick - measure_start);
+ sample_index++;
+ if (sample_index == NR_SAMPLES)
+ {
+ uint32_t min = samples[0];
+ uint32_t max = samples[0];
+ uint32_t sum = 0;
+
+ for (int i = 0; i < NR_SAMPLES; i++)
+ {
+ sum += samples[i];
+ if (samples[i] > max) max = samples[i];
+ if (samples[i] < min) min = samples[i];
+ }
+ printf("Min = %d, Max = %d, Middle = %d, Avg = %d\n", min, max, (min + max) / 2, (sum / NR_SAMPLES) >> 5 << 5);
+
+ sample_index = 0;
+ }
+ }
+ last_tick = tick;
+ }
+
+
+ DVM(int pi_connection, unsigned cmp)
+ {
+ int open_return;
+
+ pi = pi_connection;
+ comparator = cmp;
+
+ last_tick = 0;
+ sample_index = 0;
+
+
+ set_mode(pi, comparator, PI_INPUT);
+ set_pull_up_down(pi, comparator, PI_PUD_OFF);
+ set_glitch_filter(pi, comparator, 200);
+
+ open_return = callback_ex(pi, comparator, EITHER_EDGE, gpio_callback, this);
+ fprintf(stderr, "Set callback returns %d.\n", open_return);
+ }
+
+};
+
+void gpio_callback(int pi, unsigned user_gpio, unsigned level, uint32_t tick, void * userdata)
+{
+ DVM *sensor;
+
+ sensor = (DVM *)userdata;
+ sensor->input_event(user_gpio, level, tick);
+}
+
+
+int main()
+{
+ int pi;
+ std::ofstream sensorfile;
+
+ pi = pigpio_start(NULL, NULL);
+ if (pi < 0)
+ {
+ // pigpio initialisation failed.
+ fprintf(stderr, "GPIO initialization failed.\n");
+
+ }
+ else
+ {
+ // pigpio initialised okay.
+ DVM sensor(pi, CMP_IN);
+
+ while (true)
+ {
+ sleep(1);
+ //printf("%.3f\r", sensor.Voltage());
+ //fflush(stdout);
+
+ }
+ pigpio_stop(pi);
+
+ }
+
+}
+
--- /dev/null
+#include <iostream>
+
+#include <stdio.h>
+#include <unistd.h>
+#include <pigpiod_if2.h>
+
+enum SerialState
+{
+ INITIAL, WAIT_START, START_BIT, AWAIT_BIT, INSIDE_BIT, PARITY_BIT, STOP_BIT
+
+};
+
+#define TSIC_INPUT 4 // The sensor is connected to GPIO 4
+
+void gpio_callback(int pi, unsigned user_gpio, unsigned level, uint32_t tick, void * userdata);
+
+class Tsic
+{
+ int pi; // Connection to pigpio daemon
+ unsigned gpio; // Input pin of the temparature sensor
+
+ uint32_t last_high_tick;
+ uint32_t last_low_tick;
+
+ uint32_t half_bit_time;
+
+ SerialState serial_state;
+
+ int bitcount;
+ unsigned char received_byte;
+ int byte_count;
+ unsigned char input_buffer[2];
+ long temperature; // T * 100
+
+public:
+
+ void input_event(unsigned level, uint32_t tick)
+ {
+
+ switch (serial_state)
+ {
+ case INITIAL:
+ if (level == 1)
+ {
+ last_high_tick = tick;
+ serial_state = WAIT_START;
+ }
+ break;
+
+ case WAIT_START:
+ if (level == 0 && tick - last_high_tick > 3000)
+ {
+ last_low_tick = tick;
+ serial_state = START_BIT;
+ }
+ break;
+
+ case START_BIT: // 2
+ if (level == 1)
+ {
+ half_bit_time = tick - last_low_tick;
+ bitcount = 0;
+ received_byte = 0;
+ serial_state = AWAIT_BIT;
+ }
+ break;
+
+ case AWAIT_BIT: // 3
+ if (level == 0)
+ {
+ last_low_tick = tick;
+ serial_state = INSIDE_BIT;
+ }
+ break;
+
+ case INSIDE_BIT: // 4
+ if (level == 1)
+ {
+ unsigned bit = 0;
+
+ if (tick - last_low_tick < half_bit_time)
+ {
+ bit = 1;
+ }
+ bitcount++;
+ if (bitcount < 9)
+ {
+ received_byte <<= 1;
+ received_byte |= bit;
+ serial_state = AWAIT_BIT;
+ }
+ else
+ {
+ input_buffer[byte_count++] = received_byte;
+ if (byte_count == 2)
+ {
+ unsigned int sensor_value = input_buffer[0] * 256 + input_buffer[1];
+ temperature = sensor_value * 20000 / 2047 - 5000;
+ std::cout << " Temperature = " << temperature << "\n";
+ byte_count = 0;
+ }
+ received_byte = 0;
+ serial_state = STOP_BIT;
+ }
+ }
+ break;
+
+ case PARITY_BIT: // 5
+ if (level == 1)
+ {
+ serial_state = STOP_BIT;
+ }
+ break;
+ case STOP_BIT: // 6
+ if (level == 0)
+ {
+ serial_state = START_BIT;
+ last_low_tick = tick;
+ }
+ break;
+ }
+ }
+
+ Tsic(int pi_connection, unsigned input)
+ {
+ pi = pi_connection;
+ gpio = input;
+
+ last_high_tick = 0;
+ last_low_tick = 0;
+
+ half_bit_time = 60;
+
+ serial_state = INITIAL;
+
+ bitcount = 0;
+ received_byte = 0;
+ byte_count = 0;
+ temperature = 0; // T * 100
+
+ set_mode(pi, gpio, PI_INPUT);
+ set_pull_up_down(pi, gpio, PI_PUD_OFF);
+
+ int open_return = callback_ex(pi, gpio, EITHER_EDGE, gpio_callback, this);
+ fprintf(stderr, "Set callback returns %d.\n", open_return);
+ }
+
+ long T()
+ {
+ return temperature;
+ }
+};
+
+void gpio_callback(int pi, unsigned user_gpio, unsigned level, uint32_t tick, void * userdata)
+{
+ Tsic *sensor;
+
+ sensor = (Tsic *)userdata;
+ sensor->input_event(level, tick);
+}
+
+
+int main()
+{
+ int pi;
+
+ pi = pigpio_start(NULL, NULL);
+ if (pi < 0)
+ {
+ // pigpio initialisation failed.
+ fprintf(stderr, "GPIO initialization failed.\n");
+
+ }
+ else
+ {
+ // pigpio initialised okay.
+ Tsic sensor(pi, TSIC_INPUT);
+
+
+ sleep(2);
+ std::cout << "The last temperature = " << sensor.T() / 100 << "." << sensor.T() % 100 << " Celcius.\n";
+ pigpio_stop(pi);
+
+ }
+
+}
+
--- /dev/null
+#include <iostream>
+#include <iomanip>
+#include <fstream>
+
+#include <stdio.h>
+#include <unistd.h>
+#include <pigpiod_if2.h>
+
+
+#define CYCLE_OUT 18 // The cycle output
+#define CMP_IN 17 // The signal from the comparator
+#define NR_SAMPLES 20 // Number of samples to avaerage out the jitter
+
+void gpio_callback(int pi, unsigned user_gpio, unsigned level, uint32_t tick, void * userdata);
+
+#define INPUT_OFFSET 0.97
+#define INPUT_DIVIDER 0.086
+#define SLOPE_FACTOR 11.4 // Current / Capacitance
+
+class DVM
+{
+ int pi; // Connection to pigpio daemon
+ unsigned cycle_gate; // The gate to run a measurement cycle
+ unsigned comparator; // The signal from the comparator
+
+
+ uint32_t last_tick;
+ uint32_t measure_start;
+
+ uint32_t samples[NR_SAMPLES];
+ int sample_index;
+
+ float U; // The measured voltage
+
+
+public:
+
+ void input_event(unsigned gpio, unsigned level, uint32_t tick)
+ {
+ float measure_time;
+
+ //printf("Input event: input %u = %u, %d\n", gpio, level, tick - last_tick);
+
+ if (gpio == cycle_gate && level == 1)
+ {
+ measure_start = tick;
+ }
+
+ if (gpio == comparator && level == 1)
+ {
+ samples[sample_index++] = tick - measure_start;
+ sample_index %= NR_SAMPLES;
+
+ measure_time = (float)(tick - measure_start) / 1.0e6;
+ U = measure_time * 11.4 - INPUT_OFFSET;
+ U /= INPUT_DIVIDER;
+
+ gpio_write(pi, cycle_gate, 0);
+ }
+ if (gpio == comparator && level == 0)
+ {
+ gpio_write(pi, cycle_gate, 1);
+ }
+ last_tick = tick;
+ }
+
+
+ DVM(int pi_connection, unsigned gate, unsigned cmp)
+ {
+ int open_return;
+
+ pi = pi_connection;
+ cycle_gate = gate;
+ comparator = cmp;
+
+ last_tick = 0;
+ sample_index = 0;
+
+
+ set_mode(pi, comparator, PI_INPUT);
+ set_mode(pi, cycle_gate, PI_OUTPUT);
+ set_pull_up_down(pi, comparator, PI_PUD_OFF);
+
+ open_return = callback_ex(pi, cycle_gate, EITHER_EDGE, gpio_callback, this);
+ //fprintf(stderr, "Set callback returns %d.\n", open_return);
+ open_return = callback_ex(pi, comparator, EITHER_EDGE, gpio_callback, this);
+ //fprintf(stderr, "Set callback returns %d.\n", open_return);
+ gpio_write(pi, cycle_gate, 0);
+ sleep(1);
+ gpio_write(pi, cycle_gate, 1);
+ }
+
+ float Voltage()
+ {
+ uint32_t sum = 0;
+ uint32_t average_time;
+ float measure_time;
+
+ // To filter out the jitter, calculate the average measured time
+
+ for (int i = 0; i < NR_SAMPLES; i++)
+ {
+ sum += samples[i];
+ }
+
+ average_time = (sum / NR_SAMPLES) >> 5 << 5;
+ std::cout << " Average time = " << average_time << "\n";
+ measure_time = average_time / 1.0e6;
+ U = measure_time * SLOPE_FACTOR - INPUT_OFFSET;
+ U /= INPUT_DIVIDER;
+
+ return U;
+ }
+};
+
+void gpio_callback(int pi, unsigned user_gpio, unsigned level, uint32_t tick, void * userdata)
+{
+ DVM *sensor;
+
+ sensor = (DVM *)userdata;
+ sensor->input_event(user_gpio, level, tick);
+}
+
+
+int main()
+{
+ int pi;
+ std::ofstream sensorfile;
+
+ pi = pigpio_start(NULL, NULL);
+ if (pi < 0)
+ {
+ // pigpio initialisation failed.
+ fprintf(stderr, "GPIO initialization failed.\n");
+
+ }
+ else
+ {
+ // pigpio initialised okay.
+ DVM sensor(pi, CYCLE_OUT, CMP_IN);
+
+ while (true)
+ {
+ sleep(1);
+ printf("%.3f\n", sensor.Voltage());
+ fflush(stdout);
+
+ sensorfile.open("sensor1");
+ sensorfile << std::fixed << std::setprecision(1) << sensor.Voltage() << "\n";
+ sensorfile.close();
+ }
+ pigpio_stop(pi);
+
+ }
+
+}
+
projects / sensors.git / commitdiff
