Getting bitmaps to display on Adafruit TFT display

Hey all,

I’m trying to get one of these displays with the Sparkcore to try to read a .bmp file off of the display’s microSD port. I can get the display to work with non-bitmap graphics operations using a ported library, but getting the bitmaps to display requires using the SD library. I tried using the Core’s sd-card-library as a replacement, but it does not compile when using the example code from adafruit. Has anyone gotten this screen or a similar one to load bitmaps using the Core?
If so, any guidance would be greatly appreciated!

Here’s the error log if it’s helpful:

screen_things.cpp:112:20: error: 'read16' cannot be used as a function
screen_things.cpp:113:66: error: 'read32' cannot be used as a function
screen_things.cpp:114:25: error: 'read32' cannot be used as a function

screen_things.cpp:115:36: error: 'read32' cannot be used as a function
// Open requested file on SD card
screen_things.cpp:118:68: error: 'read32' cannot be used as a function
screen_things.cpp:119:31: error: 'read32' cannot be used as a function
screen_things.cpp:120:31: error: 'read32' cannot be used as a function

screen_things.cpp:121:22: error: 'read16' cannot be used as a function
// Parse BMP header
screen_things.cpp:122:32: error: 'read16' cannot be used as a function
if(read16(bmpFile) == 0x4D42) { // BMP signature
screen_things.cpp:124:45: error: 'read32' cannot be used as a function
(void)read32(bmpFile); // Read & ignore creator bytes
screen_things.cpp:149:9: error: 'tft' was not declared in this scope
flip = false;
screen_things.cpp: In function 'uint16_t read16(File&)':
screen_things.cpp:197:24: error: 'uint16_t read16(File&)' redeclared as different kind of symbol
screen_things.cpp:8:10: error: previous declaration of 'uint16_t read16'
uint16_t read16(File &f);
screen_things.cpp: In function 'uint32_t read32(File&)':
screen_things.cpp:204:24: error: 'uint32_t read32(File&)' redeclared as different kind of symbol
// BMP data is stored little-endian, Arduino is little-endian too.
screen_things.cpp:9:10: error: previous declaration of 'uint32_t read32'
uint32_t read32(File &f);
make: *** [screen_things.o] Error 1

@andrewrc, the read16 and read32 errors can be fixed by adding function prototypes at the top of screen_things.cpp, just before setup():

uint16_t read16(File & f);
uint32_t read32(File & f);

I am not sure what is causing the “tft not declared” error. :smile:

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The tft error was just a naming inconsistency in my code that I fixed.

Thanks so much for your help!

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Hello folks,

I’m new to Spark and to the hardware world in general. While building some Hello World examples, I have bumped into in issue where I can really use some help.

I’m trying to get Adafruit’s 2.8" TFT LCD to display their sample BMP image from an SD card using the Web IDE. Nevertheless the closest that I get to see those flowers is a corrupt looking file as you can see in the image below.

I’m using @peekay123 ILI9341_SPI_LCD and mfGFX libraries. As well as the SD-CARD-LIBRARY library that is available in the Web IDE.

I’m able to open the connection to the SD card. I have been able to read and write to a text file. But when I try to read and image I get several CMD17 ReadData errors. I have no idea why this is happening. Has anybody gotten a similar error?

Here is the ino file in case it is useful:

#include "Adafruit_mfGFX/Adafruit_mfGFX.h"
#include "Adafruit_ILI9341.h"
#include "sd-card-library/sd-card-library.h"
#include "application.h"

#define TFT_RST -1
#define TFT_DC A1
#define TFT_CS A2
#define SD_CS D1

Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC, TFT_RST);

uint16_t read16(File &f);
uint32_t read32(File &f);

void setup(void) {
    while (!Serial.available()) SPARK_WLAN_Loop();

  Serial.print("Initializing SD card...");
  if (!SD.begin(SD_CS)) {

  bmpDraw("purple.bmp", 0, 0);

void loop() {

// This function opens a Windows Bitmap (BMP) file and
// displays it at the given coordinates.  It's sped up
// by reading many pixels worth of data at a time
// (rather than pixel by pixel).  Increasing the buffer
// size takes more of the Arduino's precious RAM but
// makes loading a little faster.  20 pixels seems a
// good balance.

#define BUFFPIXEL 20

// Pass 8-bit (each) R,G,B, get back 16-bit packed color

void bmpDraw(char *filename, uint8_t x, uint16_t y) {

  File     bmpFile;
  int      bmpWidth, bmpHeight;   // W+H in pixels
  uint8_t  bmpDepth;              // Bit depth (currently must be 24)
  uint32_t bmpImageoffset;        // Start of image data in file
  uint32_t rowSize;               // Not always = bmpWidth; may have padding
  uint8_t  sdbuffer[3*BUFFPIXEL]; // pixel buffer (R+G+B per pixel)
  uint8_t  buffidx = sizeof(sdbuffer); // Current position in sdbuffer
  boolean  goodBmp = false;       // Set to true on valid header parse
  boolean  flip    = true;        // BMP is stored bottom-to-top
  int      w, h, row, col;
  uint8_t  r, g, b;
  uint32_t pos = 0, startTime = millis();

  if((x >= tft.width()) || (y >= tft.height())) return;

  Serial.print(F("Loading image '"));

  // Open requested file on SD card
  if ((bmpFile = == NULL) {
    Serial.print(F("File not found"));
  // Parse BMP header
  if(read16(bmpFile) == 0x4D42) { // BMP signature
    Serial.print(F("File size: ")); Serial.println(read32(bmpFile));
    (void)read32(bmpFile); // Read & ignore creator bytes
    bmpImageoffset = read32(bmpFile); // Start of image data
    Serial.print(F("Image Offset: ")); Serial.println(bmpImageoffset, DEC);
    // Read DIB header
    Serial.print(F("Header size: ")); Serial.println(read32(bmpFile));
    bmpWidth  = read32(bmpFile);
    bmpHeight = read32(bmpFile);
    if(read16(bmpFile) == 1) { // # planes -- must be '1'
      bmpDepth = read16(bmpFile); // bits per pixel
      Serial.print(F("Bit Depth: ")); Serial.println(bmpDepth);
      if((bmpDepth == 24) && (read32(bmpFile) == 0)) { // 0 = uncompressed

        goodBmp = true; // Supported BMP format -- proceed!
        Serial.print(F("Image size: "));

        // BMP rows are padded (if needed) to 4-byte boundary
        rowSize = (bmpWidth * 3 + 3) & ~3;

        // If bmpHeight is negative, image is in top-down order.
        // This is not canon but has been observed in the wild.
        if(bmpHeight < 0) {
          bmpHeight = -bmpHeight;
          flip      = false;
        // Crop area to be loaded
        w = bmpWidth;
        h = bmpHeight;
        if((x+w-1) >= tft.width())  w = tft.width()  - x;
        if((y+h-1) >= tft.height()) h = tft.height() - y;

        // Set TFT address window to clipped image bounds
        tft.setAddrWindow(x, y, x+w-1, y+h-1);
        for (row=0; row<h; row++) { // For each scanline...
          // Seek to start of scan line.  It might seem labor-
          // intensive to be doing this on every line, but this
          // method covers a lot of gritty details like cropping
          // and scanline padding.  Also, the seek only takes
          // place if the file position actually needs to change
          // (avoids a lot of cluster math in SD library).
          if(flip) // Bitmap is stored bottom-to-top order (normal BMP)
            pos = bmpImageoffset + (bmpHeight - 1 - row) * rowSize;
          else     // Bitmap is stored top-to-bottom
            pos = bmpImageoffset + row * rowSize;
          if(bmpFile.position() != pos) { // Need seek?
            buffidx = sizeof(sdbuffer); // Force buffer reload
          for (col=0; col<w; col++) { // For each pixel...
            // Time to read more pixel data?
            if (buffidx >= sizeof(sdbuffer)) { // Indeed
    , sizeof(sdbuffer));
              buffidx = 0; // Set index to beginning
            // Convert pixel from BMP to TFT format, push to display
            b = sdbuffer[buffidx++];
            g = sdbuffer[buffidx++];
            r = sdbuffer[buffidx++];
          } // end pixel
        } // end scanline
        Serial.print(F("Loaded in "));
        Serial.print(millis() - startTime);
        Serial.println(" ms");
      } // end goodBmp

  if(!goodBmp) Serial.println(F("BMP format not recognized."));

// These read 16- and 32-bit types from the SD card file.
// BMP data is stored little-endian, Arduino is little-endian too.
// May need to reverse subscript order if porting elsewhere.

uint16_t read16(File &f) {
  uint16_t result;
  ((uint8_t *)&result)[0] =; // LSB
  ((uint8_t *)&result)[1] =; // MSB
  return result;

uint32_t read32(File &f) {
  uint32_t result;
  ((uint8_t *)&result)[0] =; // LSB
  ((uint8_t *)&result)[1] =;
  ((uint8_t *)&result)[2] =;
  ((uint8_t *)&result)[3] =; // MSB
  return result;

@sazp96 not sure if you got this figured out or not, we had a similar thing with the digole displays. We had to re initialize the SD every time we talked to the display… A major pain in the bum… There are some discussions about it in the digole display thread… basically it’s to do with changing spi modes

@Hootie81, one way around the SPI mode issue is to use software SPI specifying the same pins as hardware SPI (except for the CS line of course). The other device uses hardware SPI.

In the case of @andrewrc’s libraries, both the display and SD card use the same SPI mode unlike the digole/SD combo. In his case, I suspect the issue may be that both libraries set different SPI speeds. One solution is that after setting up both devices, he makes a call the SPI.setClockDivider(); with a divider that works for the “slowest” device. :smile:

Thank you for your answers @Hootie81 and @peekay123 and sorry for the late reply. After a long frustrated week trying to get this to work, I tried a different SD card. And boom, that fixed it.

For some strange reason my PC was reading the SD card well (all the the BMP images were displayed well) but when I tried to read it from the adafruit display, it didn’t work. Once I started using the new SD card (Scan Disk 8GB) the problem was fixed.

Thanks again for the help!

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