Add basic bitmap output

src/bmp.c

@@ -0,0 +1,93 @@
+#include "bmp.h"
+#include "ff.h"
+
+typedef struct
+{
+    uint8_t b;
+    uint8_t m;
+    uint32_t bitmap_file_size;
+    uint32_t reserved;
+    uint32_t bitmap_data_offset;
+} __attribute__((packed)) BMP_FileHeader_t;
+
+typedef struct
+{
+    uint32_t header_size;
+    uint16_t bitmap_width;
+    uint16_t bitmap_height;
+    uint16_t colour_planes;
+    uint16_t bits_per_pixel;
+} __attribute((packed)) BMP_CoreHeader_t;
+
+void BMP_Save(uint8_t *data, int width, int height)
+{
+    FATFS fs;
+    FIL fp;
+    FRESULT rc;
+    unsigned int bw;
+
+    rc = f_mount(&fs, "", 0);
+    if(rc)
+    {
+        return;
+    }
+
+    rc = f_open(&fp, "IMAGE.BMP", FA_WRITE | FA_CREATE_ALWAYS);
+    if(rc)
+    {
+        return;
+    }
+
+    // Rows must be padded to a multiple if 4 bytes
+    int row_size = width / 8;
+    int padding_length = (4 - (row_size % 4)) % 4;
+    uint8_t padding_bytes[4] = {0};
+    row_size += padding_length;
+
+    BMP_FileHeader_t file_header =
+    {
+        .b = 'B',
+        .m = 'M',
+        .bitmap_file_size = 14 + 12 + row_size * height,
+        .bitmap_data_offset = 14 + 12 + 6
+    };
+
+    // Use the simplest possible header
+    BMP_CoreHeader_t core_header =
+    {
+        .header_size = 12,
+        .bitmap_width = width,
+        .bitmap_height = height,
+        .colour_planes = 1,
+        .bits_per_pixel = 1
+    };
+
+    // At one bit per pixel, we need a colour table
+    uint8_t colour_table[6] =
+    {
+        0xff, 0xff, 0xff,
+        0x00, 0x00, 0x00
+    };
+
+    if(f_write(&fp, &file_header, sizeof(file_header), &bw) != FR_OK)
+        return;
+    if(f_write(&fp, &core_header, sizeof(core_header), &bw) != FR_OK)
+        return;
+    if(f_write(&fp, &colour_table, sizeof(colour_table), &bw) != FR_OK)
+        return;
+
+    // BMPs are stored with their rows from the bottom upwards
+    for(int y = height - 1; y >= 0; y--)
+    {
+        uint8_t *row = data + y * (width / 8);
+        if(f_write(&fp, row, width / 8, &bw) != FR_OK)
+            return;
+        if(padding_length != 0)
+        {
+            if(f_write(&fp, padding_bytes, padding_length, &bw) != FR_OK)
+                return;
+        }
+    }
+
+    f_close(&fp);
+}

src/bmp.h

@@ -0,0 +1,5 @@
+#pragma once
+
+#include <stdint.h>
+
+void BMP_Save(uint8_t *data, int width, int height);

src/main.c

@@ -2,12 +2,19 @@
 
 int main(void)
 {
-    RCC->APB2ENR |= RCC_APB2ENR_IOPCEN;
+    RCC->APB2ENR |= RCC_APB2ENR_IOPBEN | RCC_APB2ENR_IOPCEN;
 
     GPIOC->CRH = (GPIOC->CRH
         & ~(0x0f << (4 * PIN_SUPPLY - 32)))
         | (0x01 << (4 * PIN_SUPPLY - 32))      // Output, max. 10 MHz
         ;
+
+    GPIOB->CRL = (GPIOB->CRL
+        & ~(0x0f << (4 * PIN_SD_CARD_DETECT)))
+        | (0x08 << (4 * PIN_SD_CARD_DETECT))   // Input with pull-up/-down
+        ;
+    // Use pull-up
+    GPIOB->BSRR = (1 << PIN_SD_CARD_DETECT);
     
     GPIOC->BSRR = (1 << PIN_SUPPLY);
 
@@ -25,6 +32,8 @@ int main(void)
     LTP1245_FeedPaper(100);
     LTP1245_FeedPaper(10);
 
+    BMP_Save(ImageBuffer, CAMERA_IMAGE_WIDTH, CAMERA_IMAGE_HEIGHT);
+
     GPIOC->BRR = (1 << PIN_SUPPLY);
 
     for(;;)
@@ -32,4 +41,3 @@ int main(void)
         __WFI();
     }
 }
-

src/main.h

@@ -15,6 +15,7 @@
 #include "font_messe_duesseldorf_39.h"
 #include "font_arpegius_16.h"
 #include "font_arpegius_32.h"
+#include "bmp.h"
 
 int main(void);
 

src/pinning.h

@@ -18,10 +18,13 @@
 
 // Port B
 #define PIN_THERMISTOR          0   // PB0  - Thermistor (ADC12_IN8)
+#define PIN_SD_SCK              1   // PB1  - SD card SCK
+#define PIN_SD_CARD_DETECT      2   // PB2  - SD card detect
 #define PIN_PAPER               3   // PB3  - Paper detect
 #define PIN_CAMERA_PCLK         4   // PB4  - Camera pixel clock (TIM3_CH1)
 #define PIN_CAMERA_HSYNC        5   // PB5  - Camera VSYNC (TIM3_CH2)
 #define PIN_HEAD                6   // PB6  - Head up sensor
+#define PIN_SD_MISO             7   // PB7  - SD card MISO
 #define PIN_CAMERA_SCL          8   // PB8  - Camera control I2C (I2C1_SCL)
 #define PIN_CAMERA_SDA          9   // PB9  - Camera control I2C (I2C1_SDA)
 #define PIN_DST1                10  // PB10 - Head drive signal 1 (TIM2_CH3)
@@ -32,4 +35,6 @@
 #define PIN_DIN                 15  // PB15 - Thermal printer MOSI (SPI2)
 
 // Port C
-#define PIN_SUPPLY              14  // PC14  - Voltage regulator enable
+#define PIN_SD_MOSI             13  // PC13 - SD card MOSI
+#define PIN_SUPPLY              14  // PC14 - Voltage regulator enable
+#define PIN_SD_CS               15  // PC15 - SD card chip select