Added initial support for HID DMM

98-hidraw.rules

@@ -0,0 +1,2 @@
+#Allow all to read hidraws
+KERNEL=="hidraw*", SUBSYSTEM=="hidraw", MODE="0664", GROUP="plugdev"

DMM_HID.cpp

@@ -0,0 +1,448 @@
+#include "DMM_HID.h"
+
+#include <linux/hidraw.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <libudev.h>
+
+#include <stdint.h>
+#include <poll.h>
+#include <limits>
+
+#define VENDOR_ID  0x2571
+#define PRODUCT_ID 0x4100
+
+using std::vector;
+using std::string;
+
+constexpr int DMM_BUFSIZE = 8;
+
+// Checks if a hidraw device matches the vendor id and product id
+// If *_id is < 0 - it is not checked
+bool check_hidraw_device(string dev, int vendor_id, int product_id)
+{
+	int fd;
+	int res;
+	struct hidraw_devinfo info;
+	bool result = false;
+	bool vendor = true;
+	bool product = true;
+
+	fd = open(dev.c_str(), O_RDONLY | O_NONBLOCK);
+	if (fd < 0)
+	{
+		return false;
+	}
+
+	memset(&info, 0, sizeof(info));
+
+	// Get Raw Info
+	res = ioctl(fd, HIDIOCGRAWINFO, &info);
+	if (res >= 0)
+	{
+		if ((vendor_id > 0) && (vendor_id != info.vendor))
+		{
+			vendor = false;
+		}
+
+		if ((product_id > 0) && (product_id != info.product))
+		{
+			product = false;
+		}
+
+		if (vendor && product)
+		{
+			result = true;
+		}
+	}
+
+	close(fd);
+
+	return result;
+}
+
+// Reads exact number of bytes from a fd for X milisec
+bool read_exact(int fd, uint8_t *buf, int size, int timeout_ms)
+{
+	struct pollfd poll_fd;
+	int bytes;
+	int bytes_read;
+
+	if ((fd < 0) || (nullptr == buf) || (size <= 0) || (timeout_ms <= 0))
+	{
+		return false;
+	}
+
+	poll_fd.fd = fd;
+	poll_fd.events = POLLIN;
+
+	bytes_read = 0;
+	while (bytes_read < size)
+	{
+		bytes = poll(&poll_fd, 1, timeout_ms);
+		if (bytes < 1)
+		{
+			return false;
+		}
+
+		bytes = read(fd, buf + bytes_read, size - bytes_read);
+		if (bytes < 1)
+		{
+			return false;
+		}
+
+		bytes_read += bytes;
+	}
+
+	return true;
+}
+
+
+vector<string> DMM_HID::get_dmm_devices()
+{
+	vector<string> result;
+	struct udev *udev_handle = nullptr;
+	struct udev_enumerate *udev_enum_handle = nullptr;
+	struct udev_list_entry *udev_entry = nullptr;
+	struct udev_device *device = nullptr;
+	const char *syspath = nullptr;
+	string path;
+	int err;
+
+	// Create udev
+	udev_handle = udev_new();
+	if (nullptr == udev_handle)
+	{
+		return result;
+	}
+
+	// Create enumerator
+	udev_enum_handle = udev_enumerate_new(udev_handle);
+	if (nullptr == udev_enum_handle)
+	{
+		goto udev_out;
+	}
+
+	// Search only for "hidraw" devices
+	err = udev_enumerate_add_match_subsystem(udev_enum_handle, "hidraw");
+	if (err < 0)
+	{
+		goto udev_out;
+	}
+
+	// Scan devices
+	err = udev_enumerate_scan_devices(udev_enum_handle);
+	if (err < 0)
+	{
+		goto udev_out;
+	}
+
+	udev_entry = udev_enumerate_get_list_entry(udev_enum_handle);
+	if (nullptr == udev_entry)
+	{
+		goto udev_out;
+	}
+
+	// Iterate through devices
+	while (nullptr != udev_entry)
+	{
+		// Name is syspath
+		syspath = udev_list_entry_get_name(udev_entry);
+		if (nullptr != syspath)
+		{
+			device = udev_device_new_from_syspath(udev_handle, syspath);
+			if (nullptr != device)
+			{
+				// devnode is needed /dev/hidraw* path
+				path = udev_device_get_devnode(device);
+
+				// Check vendor id and product id pair
+				// There's no exit from the loop
+				// so it will return the last found device
+				if (check_hidraw_device(path, VENDOR_ID, PRODUCT_ID))
+				{
+					result.push_back(path);
+				}
+
+				udev_device_unref(device);
+			}
+		}
+		udev_entry = udev_list_entry_get_next(udev_entry);
+	}
+
+udev_out:
+	// Cleanup
+	if (nullptr != udev_enum_handle)
+	{
+		udev_enumerate_unref(udev_enum_handle);
+	}
+	udev_unref(udev_handle);
+
+	return result;
+}
+
+DMM_HID::DMM_HID()
+:m_fd(-1)
+{
+
+}
+
+DMM_HID::~DMM_HID()
+{
+	Close();
+}
+
+void DMM_HID::Open(const std::string& dev)
+{
+	int fd;
+
+	if (is_open())
+	{
+		Close();
+	}
+
+	fd = open(dev.c_str(), O_RDONLY);
+	if (fd < 0)
+	{
+		return;
+	}
+
+	m_fd = fd;
+}
+
+void DMM_HID::Close()
+{
+	if (is_open())
+	{
+		close(m_fd);
+	}
+
+	m_fd = -1;
+}
+
+bool DMM_HID::is_open()
+{
+	if (m_fd < 0)
+	{
+		return false;
+	}
+
+	return true;
+}
+
+vector<Reading> DMM_HID::get_readings(int timeout_ms)
+{
+	vector<Reading> result;
+	uint8_t buf[DMM_BUFSIZE];
+	Reading reading;
+
+	if (m_fd < 0)
+	{
+		return result;
+	}
+
+	while(read_exact(m_fd, buf, DMM_BUFSIZE, timeout_ms))
+	{
+		reading.value[0] = 0;
+		reading.value[1] = 0;
+		reading.value[2] = 0;
+		reading.value[3] = 0;
+		reading.modifier = 0;
+		reading.dot_pos = 0;
+		reading.is_inf = false;
+		reading.is_neg = false;
+		reading.is_DC = false;
+		reading.is_rel = false;
+		reading.is_hold = false;
+		reading.is_min = false;
+		reading.is_max = false;
+		reading.type = Reading::reading_type_max;
+
+		// Check for infinity
+		if ((0x4F == buf[1]) && (0x4C == buf[2]))
+		{
+			reading.is_inf = true;
+		}
+
+		// BCD 4-bit values
+		reading.value[0] = (buf[1] >> 4);
+		reading.value[1] = (buf[1] & 0x0F);
+		reading.value[2] = (buf[2] >> 4);
+		reading.value[3] = (buf[2] & 0x0F);
+
+		// Byte 0 Bit 6 - Negative
+		if (buf[0] & 0x40)
+		{
+			reading.is_neg = true;
+		}
+
+		// Byte 0 second half - Dot position
+		{
+			switch (buf[0] & 0x0F)
+			{
+			case 0:
+				// Do nothing
+				break;
+
+			case 1:
+				reading.dot_pos = 1;
+				break;
+
+			case 2:
+				reading.dot_pos = 2;
+				break;
+
+			case 3:
+				reading.dot_pos = 3;
+				break;
+
+			case 4:
+				reading.dot_pos = 3;
+				break;
+
+			case 7:
+				// Assuming 3&4 overlap
+				reading.dot_pos = 3;
+				break;
+
+			default:
+				// Do nothing
+				break;
+			}
+		}
+
+		// Unit Modifier
+		{
+			// Byte 4 Bit 1
+			if (buf[4] & 0x02)
+			{
+				// nano = 10^-9
+				reading.modifier = -9;
+			}
+			// Byte 5 Bit 7
+			else if (buf[5] & 0x80)
+			{
+				// micro = 10^-6
+				reading.modifier = -6;
+			}
+			// Byte 5 Bit 6
+			else if (buf[5] & 0x40)
+			{
+				// mili = 10^-3
+				reading.modifier = -3;
+			}
+			// Byte 5 Bit 5
+			else if (buf[5] & 0x20)
+			{
+				// kilo = 10^3
+				reading.modifier = 3;
+			}
+			// Byte 5 Bit 4
+			else if (buf[5] & 0x10)
+			{
+				// mega = 10^6
+				reading.modifier = 6;
+			}
+		}
+
+		// AC/DC
+		// Byte 3 Bit 4
+		if (buf[3] & 0x10)
+		{
+			reading.is_DC = true;
+		}
+
+		// Hold / min / max / rel
+		{
+			// Byte 3 Bit 1
+			if (buf[3] & 0x02)
+			{
+				reading.is_hold = true;
+			}
+
+			// Byte 3 Bit 2
+			if (buf[3] & 0x04)
+			{
+				reading.is_rel = true;
+			}
+
+			// Byte 4 Bit 5
+			if (buf[4] & 0x20)
+			{
+				reading.is_max = true;
+			}
+
+			// Byte 4 Bit 4
+			if (buf[4] & 0x10)
+			{
+				reading.is_min = true;
+			}
+		}
+
+		// Reading type
+		{
+			// if (buf[5] & 0x08)
+			// {
+			// 	reading.type = Reading::reading_continuity;
+			// }
+			// else if (buf[5] & 0x04)
+			// {
+			// 	reading.type = Reading::reading_diode;
+			// }
+			// else
+			if (buf[5] & 0x02)
+			{
+				reading.type = Reading::reading_percent;
+			}
+			else if (buf[6] & 0x80)
+			{
+				reading.type = Reading::reading_volts;
+			}
+			else if (buf[6] & 0x40)
+			{
+				reading.type = Reading::reading_amps;
+			}
+			else if (buf[6] & 0x20)
+			{
+				reading.type = Reading::reading_ohms;
+			}
+			else if (buf[6] & 0x10)
+			{
+				reading.type = Reading::reading_hFE;
+			}
+			else if (buf[6] & 0x08)
+			{
+				reading.type = Reading::reading_hertz;
+			}
+			else if (buf[6] & 0x04)
+			{
+				reading.type = Reading::reading_farads;
+			}
+			else if (buf[6] & 0x02)
+			{
+				reading.type = Reading::reading_celsius;
+			}
+			else if (buf[6] & 0x01)
+			{
+				reading.type = Reading::reading_fahrenheit;
+			}
+		}
+
+		result.push_back(reading);
+	}
+
+	return result;
+}
+
+void DMM_HID::lock()
+{
+	m_mutex.lock();
+}
+
+void DMM_HID::unlock()
+{
+	m_mutex.unlock();
+}

DMM_HID.h

@@ -0,0 +1,75 @@
+#ifndef DMM_HID_H_
+#define DMM_HID_H_
+
+#include <mutex>
+#include <string>
+#include <vector>
+
+constexpr int DMM_TIMEOUT_MS = 100;
+
+struct Reading
+{
+	enum reading_type
+	{
+		reading_continuity,
+		reading_diode,
+		reading_percent,
+		reading_volts,
+		reading_amps,
+		reading_ohms,
+		reading_hFE,
+		reading_hertz,
+		reading_farads,
+		reading_celsius,
+		reading_fahrenheit,
+		reading_type_max
+	};
+
+	uint8_t value[4];
+	int8_t modifier;
+	uint8_t dot_pos;
+	bool is_inf;
+	bool is_neg;
+	bool is_DC;
+	bool is_rel;
+	bool is_hold;
+	bool is_min;
+	bool is_max;
+	reading_type type;
+};
+
+class DMM_HID
+{
+private:
+	// File descriptor to DMM device
+	int m_fd;
+
+	std::mutex m_mutex;
+
+public:
+	DMM_HID();
+	~DMM_HID();
+
+	// Opens the dev file and prepares to get readings
+	// Returns true on success, false on failure
+	void Open(const std::string& dev);
+
+	// Closes the dev file
+	void Close();
+
+	bool is_open();
+
+	// Returns all readings since opening or since last call
+	std::vector<Reading> get_readings(int timeout_ms = DMM_TIMEOUT_MS);
+
+	// Returns all devpaths to DMM devices
+	static std::vector<std::string> get_dmm_devices();
+
+	// Locks the mutex
+	void lock();
+
+	// Unlocks the mutex
+	void unlock();
+};
+
+#endif // DMM_H_

Makefile

@@ -0,0 +1,24 @@
+src_hid += main_hid.cpp
+src_hid += DMM_HID.cpp
+src_hid += common.cpp
+
+#src_serial += main_serial.cpp
+#src_serial += DMM_Serial.cpp
+#src_serial += common.cpp
+
+libs += -lSDL2
+libs += -lSDL2_ttf
+
+libs_hid += -ludev
+
+all:
+	make hid
+#	make serial
+
+hid:
+	g++ -o dmm_hid ${src_hid} ${libs} ${libs_hid} -DUSE_HID -Wall -Wextra -Wpedantic
+
+#serial:
+#	g++ -o dmm_serial ${src_serial} ${libs} -DUSE_Serial -Wall -Wextra -Wpedantic
+
+.PHONY: all hid serial

README.md

@@ -1,3 +1,22 @@
-# dmm_display
+# DMM Display
+Reads measurements from PeakTech 2025 and uses SDL to display it on screen
+The DMM has 2 types of interfaces:
+* HID
+* Serial
 
-Reads measurements from PeakTech 2025 and uses SDL to display it on screen
+# Requirements
+`sudo apt install libsdl2-dev libsdl2-ttf-dev`
+
+# Compiling
+`make hid`
+or
+`make serial`
+
+# Notes
+When using HID you need to add hidraw rules in order to use without sudo
+`sudo cp 98-hidraw.rules /etc/udev/rules.d/`
+`sudo udevadm control --reload-rules`
+`sudo udevadm trigger`
+
+# TODO
+No serial support yet

common.cpp

@@ -0,0 +1,207 @@
+#include "common.h"
+
+#include <iostream>
+
+using std::cout;
+using std::endl;
+
+bool init_sdl(SDL_Window **window)
+{
+	if (nullptr == window)
+	{
+		cout << "Nowhere to store window" << endl;
+		return false;
+	}
+
+	// SDL Initialization
+	if (SDL_Init(SDL_INIT_VIDEO) < 0)
+	{
+		cout << "SDL could not initialize! SDL - " << SDL_GetError() << endl;
+		return false;
+	}
+
+	(*window) = SDL_CreateWindow("DMM Display",
+		SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
+		1280, 720,
+		SDL_WINDOW_SHOWN);
+	if (nullptr == (*window))
+	{
+		cout << "Window could not be created! SDL - " << SDL_GetError() << endl;
+		SDL_Quit();
+		return false;
+	}
+
+	if (0 != TTF_Init())
+	{
+		cout << "Could not init TTF! SDL - "<< SDL_GetError() << endl;
+		SDL_DestroyWindow(*window);
+		SDL_Quit();
+		return false;
+	}
+
+	return true;
+}
+
+void quit_sdl(SDL_Window *window)
+{
+	TTF_Quit();
+	SDL_DestroyWindow(window);
+	SDL_Quit();
+}
+
+bool check_quit()
+{
+	SDL_Event e;
+
+	while(SDL_PollEvent(&e))
+	{
+		if (SDL_QUIT == e.type)
+		{
+			return true;
+		}
+	}
+
+	return false;
+}
+
+void calc_text(std::string& text, std::vector<Reading>& readings)
+{
+	if (readings.empty())
+	{
+		return;
+	}
+
+	Reading last = *(readings.rbegin());
+	text = "";
+
+	if (last.is_neg)
+	{
+		text += '-';
+	}
+	else
+	{
+		text += ' ';
+	}
+
+	if (last.is_inf)
+	{
+		text += "  O L  ";
+	}
+	else
+	{
+		for (int i = 0; i < 4; ++i)
+		{
+			text += ('0' + last.value[i]);
+			text += ' ';
+		}
+		text.erase(text.size() - 1);
+	}
+
+	if (last.dot_pos != 0)
+	{
+		text[last.dot_pos * 2] = '.';
+	}
+
+	switch (last.modifier)
+	{
+	case -9:
+		text += 'n';
+		break;
+
+	case -6:
+		text += "μ";
+		break;
+
+	case -3:
+		text += 'm';
+		break;
+
+	case 0:
+		text += ' ';
+		break;
+
+	case 3:
+		text += 'k';
+		break;
+
+	case 6:
+		text += 'M';
+		break;
+
+	default:
+		text += ' ';
+		break;
+	}
+
+	switch (last.type)
+	{
+	case Reading::reading_percent:
+		text += "%  ";
+		break;
+
+	case Reading::reading_volts:
+		text += "V  ";
+		break;
+
+	case Reading::reading_amps:
+		text += "A  ";
+		break;
+
+	case Reading::reading_ohms:
+		text += "Ω  ";
+		break;
+
+	case Reading::reading_hFE:
+		text += "hFE";
+		break;
+
+	case Reading::reading_hertz:
+		text += "Hz ";
+		break;
+
+	case Reading::reading_farads:
+		text += "F  ";
+		break;
+
+	case Reading::reading_celsius:
+		text += "°C ";
+		break;
+	
+	case Reading::reading_fahrenheit:
+		text += "°F ";
+		break;
+	
+	default:
+		text += "???";
+		break;
+	}
+}
+
+void draw_text(const std::string& text, SDL_Surface *surface, TTF_Font *font)
+{
+	SDL_Surface *txt_surface;
+	SDL_Rect rect;
+	SDL_Color fg;
+	SDL_Color bg;
+
+	fg.r = 0;
+	fg.g = 0;
+	fg.b = 0;
+
+	bg.r = 255;
+	bg.g = 255;
+	bg.b = 255;
+
+	if ((NULL == surface) || (NULL == font) || (0 == text.size()))
+	{
+		return;
+	}
+
+	txt_surface = TTF_RenderUTF8_Shaded(font, text.c_str(), fg, bg);
+
+	rect.x = 0;
+	rect.y = surface->h / 2 - txt_surface->h / 2;
+
+	SDL_BlitSurface(txt_surface, NULL, surface, &rect);
+	SDL_FreeSurface(txt_surface);
+}

common.h

@@ -0,0 +1,22 @@
+#ifndef COMMON_H_
+#define COMMON_H_
+
+#include <string>
+#include <vector>
+
+#include <SDL2/SDL.h>
+#include <SDL2/SDL_ttf.h>
+
+#ifdef USE_HID
+# include "DMM_HID.h"
+#endif
+
+#define UI_FPS 30
+
+bool init_sdl(SDL_Window **window);
+void quit_sdl(SDL_Window *window);
+bool check_quit();
+void calc_text(std::string& text, std::vector<Reading>& readings);
+void draw_text(const std::string& text, SDL_Surface *surface, TTF_Font *font);
+
+#endif // COMMON_H_

main_hid.cpp

@@ -0,0 +1,113 @@
+#include <iostream>
+#include <memory>
+#include <thread>
+
+#include "DMM_HID.h"
+#include "common.h"
+
+using std::cout;
+using std::endl;
+using std::string;
+using std::vector;
+
+bool open_dmm(DMM_HID& dmm)
+{
+	vector<string> devs = DMM_HID::get_dmm_devices();
+	vector<Reading> readings;
+
+	if (0 == devs.size())
+	{
+		cout << "DMM not found" << endl;
+		return false;
+	}
+
+	if (devs.size() > 1)
+	{
+		cout << "Multiple DMMs found" << endl;
+		cout << "Using: " << devs[0] << endl;
+	}
+
+	dmm.Open(devs[0]);
+
+	// Wait a sec
+	std::this_thread::sleep_for(std::chrono::seconds(1));
+
+	// DMM is open. Now check its config
+	readings = dmm.get_readings(1);
+
+	if (readings.empty())
+	{
+		cout << "DMM communication is not ON - Press and hold USB/REL key" << endl;
+	}
+
+	return true;
+}
+
+int main(int argc, char **argv)
+{
+	bool ok;
+	bool quit = false;
+
+	DMM_HID dmm;
+	vector<Reading> readings;
+
+	Uint32 next_draw = 0;
+	Uint32 ms;
+
+	SDL_Window *window;
+	SDL_Surface *surface;
+	TTF_Font *font;
+
+	string text;
+
+	// Keep compiler happy
+	(void)argc;
+	(void)argv;
+
+	ok = open_dmm(dmm);
+	if (!ok)
+	{
+		return -1;
+	}
+
+	ok = init_sdl(&window);
+	if (!ok)
+	{
+		return -1;
+	}
+
+	font = TTF_OpenFont("./font.ttf", 100);
+
+	while (!quit)
+	{
+		ms = SDL_GetTicks();
+		if (next_draw - ms > 1000 / UI_FPS)
+		{
+			surface = SDL_GetWindowSurface(window);
+
+			// Fill the surface white
+			SDL_FillRect(surface, NULL, SDL_MapRGB(surface->format, 255, 255, 255));
+
+			// Get Readings
+			readings = dmm.get_readings();
+
+			// Calculate Text
+			calc_text(text, readings);
+
+			// TODO: Draw Text
+			draw_text(text, surface, font);
+
+			next_draw = ms + 1000 / UI_FPS;
+
+			// Update the window
+			SDL_UpdateWindowSurface(window);
+
+			quit = check_quit();
+		}
+	}
+
+	TTF_CloseFont(font);
+	quit_sdl(window);
+
+	return 0;
+}