Improved readme.

Author: cnadler86

README.md

@@ -16,6 +16,7 @@ If you are not familiar with building a custom firmware, you can go to the [rele
 from camera import Camera, GrabMode, PixelFormat, FrameSize, GainCeiling
 
 # Camera construction and initialization
+# These pins are just examples and if you use them just like that will get a watchdog error. Adapt them to your board!
 camera = Camera(
     data_pins=[1,2,3,4,5,6,7,8],
     vsync_pin=9,
@@ -87,12 +88,12 @@ Example for Xiao sense:
 #define MICROPY_CAMERA_PIN_XCLK     (10)
 #define MICROPY_CAMERA_PIN_PWDN     (-1)
 #define MICROPY_CAMERA_PIN_RESET    (-1)
-#define MICROPY_CAMERA_PIN_SIOD     (40)
-#define MICROPY_CAMERA_PIN_SIOC     (39)
-#define MICROPY_CAMERA_XCLK_FREQ    (20000000)
-#define MICROPY_CAMERA_FB_COUNT     (2)
-#define MICROPY_CAMERA_JPEG_QUALITY (10)
-#define MICROPY_CAMERA_GRAB_MODE    (1)
+#define MICROPY_CAMERA_PIN_SIOD     (40)  // SDA
+#define MICROPY_CAMERA_PIN_SIOC     (39)  // SCL
+#define MICROPY_CAMERA_XCLK_FREQ    (20000000)  // Frequencies are normally either 10 MHz or 20 MHz
+#define MICROPY_CAMERA_FB_COUNT     (2)   // Usually the value is between 1 (slow) and 2 (fast, but more load on CPU)
+#define MICROPY_CAMERA_JPEG_QUALITY (10)  // Quality of JPEG output. 0-63 lower means higher quality. Definition will change in the future
+#define MICROPY_CAMERA_GRAB_MODE    (1)   // 0=WHEN_EMPTY (might have old data, but less resources), 1=LATEST (best, but more resources)
 
 ```
 

src/modcamera.c

@@ -290,6 +290,14 @@ const mp_rom_map_elem_t mp_camera_hal_gainceiling_table[] = {
     { MP_ROM_QSTR(MP_QSTR_128X),    MP_ROM_INT(GAINCEILING_128X) },
 };
 
+// Supporting functions
+static int map(int value, int fromLow, int fromHigh, int toLow, int toHigh) {
+    if (fromHigh == fromLow) {
+        mp_raise_ValueError(MP_ERROR_TEXT("fromLow und fromHigh shall not be equal"));
+    }
+    return (int)((int32_t)(value - fromLow) * (toHigh - toLow) / (fromHigh - fromLow) + toLow);
+}
+
 //TODO: Makros with convertion function, since the API will use standarized values.
 // Helper functions to get and set camera and sensor information
 #define SENSOR_STATUS_GETSET_IN_RANGE(type, name, status_field_name, setter_function_name, min_val, max_val) \