// GxEPD2_SD_Example : Display Library example for SPI e-paper panels from Dalian Good Display and boards from Waveshare. // Requires HW SPI and Adafruit_GFX. Caution: the e-paper panels require 3.3V supply AND data lines! // // Display Library based on Demo Example from Good Display: http://www.e-paper-display.com/download_list/downloadcategoryid=34&isMode=false.html // // BMP handling code extracts taken from: https://github.com/prenticedavid/MCUFRIEND_kbv/tree/master/examples/showBMP_kbv_Uno // // Author: Jean-Marc Zingg // // Version: see library.properties // // Library: https://github.com/ZinggJM/GxEPD2 // // note that BMP bitmaps are drawn at physical position in physical orientation of the screen // Supporting Arduino Forum Topics: // Waveshare e-paper displays with SPI: http://forum.arduino.cc/index.php?topic=487007.0 // Good Display ePaper for Arduino: https://forum.arduino.cc/index.php?topic=436411.0 // see GxEPD2_wiring_examples.h for wiring suggestions and examples // **** NOTE that the mapping suggestion may need modification depending on SD board used! **** // ******************************************************************************************** // //#define SD_CS SS // e.g. for RobotDyn Wemos D1 mini SD board //#define EPD_CS D1 // alternative I use with RobotDyn Wemos D1 mini SD board // base class GxEPD2_GFX can be used to pass references or pointers to the display instance as parameter, uses ~1.2k more code // enable or disable GxEPD2_GFX base class #define ENABLE_GxEPD2_GFX 0 // uncomment next line to use class GFX of library GFX_Root instead of Adafruit_GFX //#include // Note: if you use this with ENABLE_GxEPD2_GFX 1: // uncomment it in GxEPD2_GFX.h too, or add #include before any #include #include #include #include #include #if defined(ESP32) // has support for FAT32 support with long filenames #include "FS.h" #include "SD.h" #include "SPI.h" #define SdFile File #define seekSet seek #else // include SdFat for FAT32 support with long filenames; available through Library Manager #include SdFat SD; #endif // #define EPD_CS before #include "GxEPD2_display_selection_new_style.h" to override default #if defined (ESP8266) #define SD_CS SS // e.g. for RobotDyn Wemos D1 mini SD board #define EPD_CS D1 // alternative I use with RobotDyn Wemos D1 mini SD board #endif // select the display class and display driver class in the following file (new style): // don't forget to modify or override EPD_CS if needed #include "GxEPD2_display_selection_new_style.h" #if defined(ESP32) #define SD_CS 2 // adapted to my wiring #endif #if defined(__AVR) #define SD_CS 6 // adapt to your wiring #define EPD_CS SS // adapt to your wiring // most AVR Arduinos have not enough RAM for use with SD and buffered graphics // !!! use GxEPD2_SD_AVR_Example.ino instead !!! //GxEPD2_154 display(/*CS=10*/ EPD_CS, /*DC=*/ 8, /*RST=*/ 9, /*BUSY=*/ 7); #endif // function declaration with default parameter // note that BMP bitmaps are drawn at physical position in physical orientation of the screen void drawBitmapFromSD(const char *filename, int16_t x, int16_t y, bool with_color = true); // bitmap drawing using buffered graphics, e.g. for small bitmaps or for GxEPD2_154c // draws BMP bitmap according to set orientation // partial_update selects refresh mode (not effective for GxEPD2_154c) // overwrite = true does not clear buffer before drawing, use only if buffer is full height void drawBitmapFromSD_Buffered(const char *filename, int16_t x, int16_t y, bool with_color = true, bool partial_update = false, bool overwrite = false); void setup() { Serial.begin(115200); Serial.println(); Serial.println("GxEPD2_SD_Example"); display.init(115200); Serial.print("Initializing SD card..."); if (!SD.begin(SD_CS)) { Serial.println("SD failed!"); return; } Serial.println("SD OK!"); if ((display.epd2.panel == GxEPD2::GDEW0154Z04) || (display.epd2.panel == GxEPD2::ACeP565) || false) { drawBitmapsBuffered_200x200(); drawBitmapsBuffered_other(); } else { drawBitmaps_200x200(); drawBitmaps_other(); } //drawBitmaps_test(); //drawBitmapsBuffered_test(); Serial.println("GxEPD2_SD_Example done"); } void loop(void) { } void drawBitmaps_200x200() { int16_t x = (display.width() - 200) / 2; int16_t y = (display.height() - 200) / 2; drawBitmapFromSD("logo200x200.bmp", x, y); delay(2000); drawBitmapFromSD("first200x200.bmp", x, y); delay(2000); drawBitmapFromSD("second200x200.bmp", x, y); delay(2000); drawBitmapFromSD("third200x200.bmp", x, y); delay(2000); drawBitmapFromSD("fourth200x200.bmp", x, y); delay(2000); drawBitmapFromSD("fifth200x200.bmp", x, y); delay(2000); drawBitmapFromSD("sixth200x200.bmp", x, y); delay(2000); drawBitmapFromSD("seventh200x200.bmp", x, y); delay(2000); drawBitmapFromSD("eighth200x200.bmp", x, y); delay(2000); } void drawBitmaps_other() { int16_t w2 = display.width() / 2; int16_t h2 = display.height() / 2; drawBitmapFromSD("parrot.bmp", w2 - 64, h2 - 80); delay(2000); drawBitmapFromSD("betty_1.bmp", w2 - 100, h2 - 160); delay(2000); drawBitmapFromSD("betty_4.bmp", w2 - 102, h2 - 126); delay(2000); drawBitmapFromSD("marilyn_240x240x8.bmp", w2 - 120, h2 - 120); delay(2000); drawBitmapFromSD("miniwoof.bmp", w2 - 60, h2 - 80); delay(2000); drawBitmapFromSD("t200x200.bmp", w2 - 100, h2 - 100); delay(2000); drawBitmapFromSD("test.bmp", w2 - 120, h2 - 160); delay(2000); drawBitmapFromSD("tiger.bmp", w2 - 160, h2 - 120); delay(2000); drawBitmapFromSD("tiger_178x160x4.bmp", w2 - 89, h2 - 80); delay(2000); drawBitmapFromSD("tiger_240x317x4.bmp", w2 - 120, h2 - 160); delay(2000); drawBitmapFromSD("tiger_320x200x24.bmp", w2 - 160, h2 - 100); delay(2000); drawBitmapFromSD("tiger16T.bmp", w2 - 160, h2 - 120); delay(2000); drawBitmapFromSD("woof.bmp", w2 - 120, h2 - 160); delay(2000); drawBitmapFromSD("bitmap640x384_1.bmp", 0, 0); delay(2000); } void drawBitmaps_test() { int16_t w2 = display.width() / 2; int16_t h2 = display.height() / 2; drawBitmapFromSD("betty_4.bmp", w2 - 102, h2 - 126); delay(2000); drawBitmapFromSD("bb4.bmp", 0, 0); delay(2000); drawBitmapFromSD("output5.bmp", 0, 0); delay(2000); drawBitmapFromSD("output6.bmp", 0, 0); delay(2000); drawBitmapFromSD("tractor_1.bmp", 0, 0); delay(2000); drawBitmapFromSD("tractor_4.bmp", 0, 0); delay(2000); drawBitmapFromSD("tractor_8.bmp", 0, 0); delay(2000); drawBitmapFromSD("tractor_11.bmp", 0, 0); delay(2000); drawBitmapFromSD("tractor_44.bmp", 0, 0); delay(2000); drawBitmapFromSD("tractor_88.bmp", 0, 0); delay(2000); } void drawBitmapsBuffered_200x200() { int16_t x = (display.width() - 200) / 2; int16_t y = (display.height() - 200) / 2; drawBitmapFromSD_Buffered("logo200x200.bmp", x, y); delay(2000); drawBitmapFromSD_Buffered("first200x200.bmp", x, y); delay(2000); drawBitmapFromSD_Buffered("second200x200.bmp", x, y); delay(2000); drawBitmapFromSD_Buffered("third200x200.bmp", x, y); delay(2000); drawBitmapFromSD_Buffered("fourth200x200.bmp", x, y); delay(2000); drawBitmapFromSD_Buffered("fifth200x200.bmp", x, y); delay(2000); drawBitmapFromSD_Buffered("sixth200x200.bmp", x, y); delay(2000); drawBitmapFromSD_Buffered("seventh200x200.bmp", x, y); delay(2000); drawBitmapFromSD_Buffered("eighth200x200.bmp", x, y); delay(2000); } void drawBitmapsBuffered_other() { int16_t w2 = display.width() / 2; int16_t h2 = display.height() / 2; drawBitmapFromSD_Buffered("parrot.bmp", w2 - 64, h2 - 80); delay(2000); drawBitmapFromSD_Buffered("betty_1.bmp", w2 - 100, h2 - 160); delay(2000); drawBitmapFromSD_Buffered("betty_4.bmp", w2 - 102, h2 - 126); delay(2000); drawBitmapFromSD_Buffered("marilyn_240x240x8.bmp", w2 - 120, h2 - 120); delay(2000); drawBitmapFromSD_Buffered("miniwoof.bmp", w2 - 60, h2 - 80); delay(2000); drawBitmapFromSD_Buffered("t200x200.bmp", w2 - 100, h2 - 100); delay(2000); drawBitmapFromSD_Buffered("test.bmp", w2 - 120, h2 - 160); delay(2000); drawBitmapFromSD_Buffered("tiger.bmp", w2 - 160, h2 - 120); delay(2000); drawBitmapFromSD_Buffered("tiger_178x160x4.bmp", w2 - 89, h2 - 80); delay(2000); drawBitmapFromSD_Buffered("tiger_240x317x4.bmp", w2 - 120, h2 - 160); delay(2000); drawBitmapFromSD_Buffered("tiger_320x200x24.bmp", w2 - 160, h2 - 100); delay(2000); drawBitmapFromSD_Buffered("tiger16T.bmp", w2 - 160, h2 - 120); delay(2000); drawBitmapFromSD_Buffered("woof.bmp", w2 - 120, h2 - 160); delay(2000); drawBitmapFromSD_Buffered("bitmap640x384_1.bmp", 0, 0); delay(2000); } void drawBitmapsBuffered_test() { int16_t w2 = display.width() / 2; int16_t h2 = display.height() / 2; drawBitmapFromSD_Buffered("betty_4.bmp", w2 - 102, h2 - 126); delay(2000); drawBitmapFromSD_Buffered("bb4.bmp", 0, 0, false, true, true); delay(2000); } //static const uint16_t input_buffer_pixels = 20; // may affect performance static const uint16_t input_buffer_pixels = 800; // may affect performance static const uint16_t max_row_width = 1448; // for up to 6" display 1448x1072 static const uint16_t max_palette_pixels = 256; // for depth <= 8 uint8_t input_buffer[3 * input_buffer_pixels]; // up to depth 24 uint8_t output_row_mono_buffer[max_row_width / 8]; // buffer for at least one row of b/w bits uint8_t output_row_color_buffer[max_row_width / 8]; // buffer for at least one row of color bits uint8_t mono_palette_buffer[max_palette_pixels / 8]; // palette buffer for depth <= 8 b/w uint8_t color_palette_buffer[max_palette_pixels / 8]; // palette buffer for depth <= 8 c/w uint16_t rgb_palette_buffer[max_palette_pixels]; // palette buffer for depth <= 8 for buffered graphics, needed for 7-color display void drawBitmapFromSD(const char *filename, int16_t x, int16_t y, bool with_color) { SdFile file; bool valid = false; // valid format to be handled bool flip = true; // bitmap is stored bottom-to-top uint32_t startTime = millis(); if ((x >= display.epd2.WIDTH) || (y >= display.epd2.HEIGHT)) return; Serial.println(); Serial.print("Loading image '"); Serial.print(filename); Serial.println('\''); #if defined(ESP32) file = SD.open(String("/") + filename, FILE_READ); if (!file) { Serial.print("File not found"); return; } #else if (!file.open(filename, FILE_READ)) { Serial.print("File not found"); return; } #endif // Parse BMP header if (read16(file) == 0x4D42) // BMP signature { uint32_t fileSize = read32(file); uint32_t creatorBytes = read32(file); uint32_t imageOffset = read32(file); // Start of image data uint32_t headerSize = read32(file); uint32_t width = read32(file); uint32_t height = read32(file); uint16_t planes = read16(file); uint16_t depth = read16(file); // bits per pixel uint32_t format = read32(file); if ((planes == 1) && ((format == 0) || (format == 3))) // uncompressed is handled, 565 also { Serial.print("File size: "); Serial.println(fileSize); Serial.print("Image Offset: "); Serial.println(imageOffset); Serial.print("Header size: "); Serial.println(headerSize); Serial.print("Bit Depth: "); Serial.println(depth); Serial.print("Image size: "); Serial.print(width); Serial.print('x'); Serial.println(height); // BMP rows are padded (if needed) to 4-byte boundary uint32_t rowSize = (width * depth / 8 + 3) & ~3; if (depth < 8) rowSize = ((width * depth + 8 - depth) / 8 + 3) & ~3; if (height < 0) { height = -height; flip = false; } uint16_t w = width; uint16_t h = height; if ((x + w - 1) >= display.epd2.WIDTH) w = display.epd2.WIDTH - x; if ((y + h - 1) >= display.epd2.HEIGHT) h = display.epd2.HEIGHT - y; if (w <= max_row_width) // handle with direct drawing { valid = true; uint8_t bitmask = 0xFF; uint8_t bitshift = 8 - depth; uint16_t red, green, blue; bool whitish, colored; if (depth == 1) with_color = false; if (depth <= 8) { if (depth < 8) bitmask >>= depth; //file.seekSet(54); //palette is always @ 54 file.seekSet(imageOffset - (4 << depth)); // 54 for regular, diff for colorsimportant for (uint16_t pn = 0; pn < (1 << depth); pn++) { blue = file.read(); green = file.read(); red = file.read(); file.read(); //Serial.print(red); Serial.print(" "); Serial.print(green); Serial.print(" "); Serial.println(blue); whitish = with_color ? ((red > 0x80) && (green > 0x80) && (blue > 0x80)) : ((red + green + blue) > 3 * 0x80); // whitish colored = (red > 0xF0) || ((green > 0xF0) && (blue > 0xF0)); // reddish or yellowish? if (0 == pn % 8) mono_palette_buffer[pn / 8] = 0; mono_palette_buffer[pn / 8] |= whitish << pn % 8; if (0 == pn % 8) color_palette_buffer[pn / 8] = 0; color_palette_buffer[pn / 8] |= colored << pn % 8; } } display.clearScreen(); uint32_t rowPosition = flip ? imageOffset + (height - h) * rowSize : imageOffset; for (uint16_t row = 0; row < h; row++, rowPosition += rowSize) // for each line { uint32_t in_remain = rowSize; uint32_t in_idx = 0; uint32_t in_bytes = 0; uint8_t in_byte = 0; // for depth <= 8 uint8_t in_bits = 0; // for depth <= 8 uint8_t out_byte = 0xFF; // white (for w%8!=0 border) uint8_t out_color_byte = 0xFF; // white (for w%8!=0 border) uint32_t out_idx = 0; file.seekSet(rowPosition); for (uint16_t col = 0; col < w; col++) // for each pixel { // Time to read more pixel data? if (in_idx >= in_bytes) // ok, exact match for 24bit also (size IS multiple of 3) { in_bytes = file.read(input_buffer, in_remain > sizeof(input_buffer) ? sizeof(input_buffer) : in_remain); in_remain -= in_bytes; in_idx = 0; } switch (depth) { case 24: blue = input_buffer[in_idx++]; green = input_buffer[in_idx++]; red = input_buffer[in_idx++]; whitish = with_color ? ((red > 0x80) && (green > 0x80) && (blue > 0x80)) : ((red + green + blue) > 3 * 0x80); // whitish colored = (red > 0xF0) || ((green > 0xF0) && (blue > 0xF0)); // reddish or yellowish? break; case 16: { uint8_t lsb = input_buffer[in_idx++]; uint8_t msb = input_buffer[in_idx++]; if (format == 0) // 555 { blue = (lsb & 0x1F) << 3; green = ((msb & 0x03) << 6) | ((lsb & 0xE0) >> 2); red = (msb & 0x7C) << 1; } else // 565 { blue = (lsb & 0x1F) << 3; green = ((msb & 0x07) << 5) | ((lsb & 0xE0) >> 3); red = (msb & 0xF8); } whitish = with_color ? ((red > 0x80) && (green > 0x80) && (blue > 0x80)) : ((red + green + blue) > 3 * 0x80); // whitish colored = (red > 0xF0) || ((green > 0xF0) && (blue > 0xF0)); // reddish or yellowish? } break; case 1: case 4: case 8: { if (0 == in_bits) { in_byte = input_buffer[in_idx++]; in_bits = 8; } uint16_t pn = (in_byte >> bitshift) & bitmask; whitish = mono_palette_buffer[pn / 8] & (0x1 << pn % 8); colored = color_palette_buffer[pn / 8] & (0x1 << pn % 8); in_byte <<= depth; in_bits -= depth; } break; } if (whitish) { // keep white } else if (colored && with_color) { out_color_byte &= ~(0x80 >> col % 8); // colored } else { out_byte &= ~(0x80 >> col % 8); // black } if ((7 == col % 8) || (col == w - 1)) // write that last byte! (for w%8!=0 border) { output_row_color_buffer[out_idx] = out_color_byte; output_row_mono_buffer[out_idx++] = out_byte; out_byte = 0xFF; // white (for w%8!=0 border) out_color_byte = 0xFF; // white (for w%8!=0 border) } } // end pixel uint16_t yrow = y + (flip ? h - row - 1 : row); display.writeImage(output_row_mono_buffer, output_row_color_buffer, x, yrow, w, 1); } // end line Serial.print("loaded in "); Serial.print(millis() - startTime); Serial.println(" ms"); display.refresh(); } } } file.close(); if (!valid) { Serial.println("bitmap format not handled."); } } void drawBitmapFromSD_Buffered(const char *filename, int16_t x, int16_t y, bool with_color, bool partial_update, bool overwrite) { SdFile file; bool valid = false; // valid format to be handled bool flip = true; // bitmap is stored bottom-to-top bool has_multicolors = display.epd2.panel == GxEPD2::ACeP565; uint32_t startTime = millis(); if ((x >= display.width()) || (y >= display.height())) return; Serial.println(); Serial.print("Loading image '"); Serial.print(filename); Serial.println('\''); #if defined(ESP32) file = SD.open(String("/") + filename, FILE_READ); if (!file) { Serial.print("File not found"); return; } #else if (!file.open(filename, FILE_READ)) { Serial.print("File not found"); return; } #endif // Parse BMP header if (read16(file) == 0x4D42) // BMP signature { uint32_t fileSize = read32(file); uint32_t creatorBytes = read32(file); uint32_t imageOffset = read32(file); // Start of image data uint32_t headerSize = read32(file); uint32_t width = read32(file); uint32_t height = read32(file); uint16_t planes = read16(file); uint16_t depth = read16(file); // bits per pixel uint32_t format = read32(file); if ((planes == 1) && ((format == 0) || (format == 3))) // uncompressed is handled, 565 also { Serial.print("File size: "); Serial.println(fileSize); Serial.print("Image Offset: "); Serial.println(imageOffset); Serial.print("Header size: "); Serial.println(headerSize); Serial.print("Bit Depth: "); Serial.println(depth); Serial.print("Image size: "); Serial.print(width); Serial.print('x'); Serial.println(height); // BMP rows are padded (if needed) to 4-byte boundary uint32_t rowSize = (width * depth / 8 + 3) & ~3; if (depth < 8) rowSize = ((width * depth + 8 - depth) / 8 + 3) & ~3; if (height < 0) { height = -height; flip = false; } uint16_t w = width; uint16_t h = height; if ((x + w - 1) >= display.width()) w = display.width() - x; if ((y + h - 1) >= display.height()) h = display.height() - y; //if (w <= max_row_width) // handle with direct drawing { valid = true; uint8_t bitmask = 0xFF; uint8_t bitshift = 8 - depth; uint16_t red, green, blue; bool whitish, colored; if (depth == 1) with_color = false; if (depth <= 8) { if (depth < 8) bitmask >>= depth; //file.seekSet(54); //palette is always @ 54 file.seekSet(imageOffset - (4 << depth)); //54 for regular, diff for colorsimportant for (uint16_t pn = 0; pn < (1 << depth); pn++) { blue = file.read(); green = file.read(); red = file.read(); file.read(); whitish = with_color ? ((red > 0x80) && (green > 0x80) && (blue > 0x80)) : ((red + green + blue) > 3 * 0x80); // whitish colored = (red > 0xF0) || ((green > 0xF0) && (blue > 0xF0)); // reddish or yellowish? if (0 == pn % 8) mono_palette_buffer[pn / 8] = 0; mono_palette_buffer[pn / 8] |= whitish << pn % 8; if (0 == pn % 8) color_palette_buffer[pn / 8] = 0; color_palette_buffer[pn / 8] |= colored << pn % 8; rgb_palette_buffer[pn] = ((red & 0xF8) << 8) | ((green & 0xFC) << 3) | ((blue & 0xF8) >> 3); } } if (partial_update) display.setPartialWindow(x, y, w, h); else display.setFullWindow(); display.firstPage(); do { //if (!overwrite) display.fillScreen(GxEPD_WHITE); uint32_t rowPosition = flip ? imageOffset + (height - h) * rowSize : imageOffset; for (uint16_t row = 0; row < h; row++, rowPosition += rowSize) // for each line { uint32_t in_remain = rowSize; uint32_t in_idx = 0; uint32_t in_bytes = 0; uint8_t in_byte = 0; // for depth <= 8 uint8_t in_bits = 0; // for depth <= 8 uint16_t color = GxEPD_WHITE; file.seekSet(rowPosition); for (uint16_t col = 0; col < w; col++) // for each pixel { // Time to read more pixel data? if (in_idx >= in_bytes) // ok, exact match for 24bit also (size IS multiple of 3) { in_bytes = file.read(input_buffer, in_remain > sizeof(input_buffer) ? sizeof(input_buffer) : in_remain); in_remain -= in_bytes; in_idx = 0; } switch (depth) { case 24: blue = input_buffer[in_idx++]; green = input_buffer[in_idx++]; red = input_buffer[in_idx++]; whitish = with_color ? ((red > 0x80) && (green > 0x80) && (blue > 0x80)) : ((red + green + blue) > 3 * 0x80); // whitish colored = (red > 0xF0) || ((green > 0xF0) && (blue > 0xF0)); // reddish or yellowish? color = ((red & 0xF8) << 8) | ((green & 0xFC) << 3) | ((blue & 0xF8) >> 3); break; case 16: { uint8_t lsb = input_buffer[in_idx++]; uint8_t msb = input_buffer[in_idx++]; if (format == 0) // 555 { blue = (lsb & 0x1F) << 3; green = ((msb & 0x03) << 6) | ((lsb & 0xE0) >> 2); red = (msb & 0x7C) << 1; color = ((red & 0xF8) << 8) | ((green & 0xFC) << 3) | ((blue & 0xF8) >> 3); } else // 565 { blue = (lsb & 0x1F) << 3; green = ((msb & 0x07) << 5) | ((lsb & 0xE0) >> 3); red = (msb & 0xF8); color = (msb << 8) | lsb; } whitish = with_color ? ((red > 0x80) && (green > 0x80) && (blue > 0x80)) : ((red + green + blue) > 3 * 0x80); // whitish colored = (red > 0xF0) || ((green > 0xF0) && (blue > 0xF0)); // reddish or yellowish? } break; case 1: case 4: case 8: { if (0 == in_bits) { in_byte = input_buffer[in_idx++]; in_bits = 8; } uint16_t pn = (in_byte >> bitshift) & bitmask; whitish = mono_palette_buffer[pn / 8] & (0x1 << pn % 8); colored = color_palette_buffer[pn / 8] & (0x1 << pn % 8); in_byte <<= depth; in_bits -= depth; color = rgb_palette_buffer[pn]; } break; } if (with_color && has_multicolors) { // keep color } else if (whitish) { color = GxEPD_WHITE; } else if (colored && with_color) { color = GxEPD_COLORED; } else { color = GxEPD_BLACK; } uint16_t yrow = y + (flip ? h - row - 1 : row); display.drawPixel(x + col, yrow, color); } // end pixel } // end line Serial.print("page loaded in "); Serial.print(millis() - startTime); Serial.println(" ms"); } while (display.nextPage()); Serial.print("loaded in "); Serial.print(millis() - startTime); Serial.println(" ms"); } } } file.close(); if (!valid) { Serial.println("bitmap format not handled."); } } uint16_t read16(SdFile& f) { // BMP data is stored little-endian, same as Arduino. uint16_t result; ((uint8_t *)&result)[0] = f.read(); // LSB ((uint8_t *)&result)[1] = f.read(); // MSB return result; } uint32_t read32(SdFile& f) { // BMP data is stored little-endian, same as Arduino. uint32_t result; ((uint8_t *)&result)[0] = f.read(); // LSB ((uint8_t *)&result)[1] = f.read(); ((uint8_t *)&result)[2] = f.read(); ((uint8_t *)&result)[3] = f.read(); // MSB return result; }