Kernel interface

Warning: this is preliminary and is subject to change until release.

In case you need to write low level code (you can't/don't want to use high level libs like SDL), you can use kernel interface. This is the recommended way to access hardware (as opposed to GP2X style of accessing chip registers by mmap'ing /dev/mem), because in case hardware changes are needed in future, they could be handled by kernel and all programs would still work. It also should allow several programs to work at the same time and should be more stable.

Input

Warning: if your goal is just to read inputs use higher level libraries/interfaces like SDL, X input or similar for your own good (portability). It may be impossible to retain this layout on some major hardware revision, let's say Pandora 3000, and your program will break.

Buttons, keypad, touchscreen and nubs are all exposed through Linux event interface (EVDEV). All devices are represented by /dev/input/eventX files, which can be opened, read and queried (using ioctl calls). The reads can be synchronous (the read will only return when user does something, like presses the button), or asynchronous (the system will report what changed since the last time you asked).

Warning: don't hardcode device filenames in your program! For example, currently /dev/input/event2 represents game buttons, but in future it may become touchscreen. Scan input device names instead, example:

for (i = 0; 1; i++)
{
  sprintf(name, "/dev/input/event%i", i);
  fd = open(name, O_RDONLY);
  if (fd < 0) break; /* no more devices */
  ioctl(fd, EVIOCGNAME(sizeof(name)), name);
  if (strcmp(name, "gpio-keys") == 0)
    return fd; /* found the buttons! */
  close(fd); /* we don't need this device */
}

List of device names and events they send:

name	description	event.type	event.code	event.value
keypad	keypad	EV_KEY	KEY_0...KEY_Z, KEY_BACKSPACE, KEY_LEFTSHIFT, KEY_SPACE, KEY_ENTER, KEY_COMMA, KEY_DOT, KEY_FN	0 - released, 1 - pressed, 2 - autorepeat event
gpio-keys	game buttons	EV_KEY	KEY_UP, KEY_DOWN, KEY_LEFT, KEY_RIGHT, KEY_MENU (Pandora button), KEY_LEFTALT (Start), KEY_LEFTCTRL (Select), KEY_KP1 (Y/North), KEY_KP2 (A/East), KEY_KP3 (X/South), KEY_KP4 (B/West), KEY_KP5 (Shoulder L), KEY_KP6 (Shoulder R), KEY_KP7 (Shoulder L2), KEY_KP8 (Shoulder R2), KEY_COFFEE (Hold)	0 - released, 1 - pressed
gpio-keys	lid state	EV_SW	SW_LID	0 - closing, 1 - opening
touchscreen	touchscreen	EV_ABS	ABS_X, ABS_Y, ABS_PRESSURE	varies, use calibration data
nub0	left nub	EV_ABS	ABS_X, ABS_Y	-256 (Left/Up) ...0... +256 (Right/Down)
nub1	right nub	EV_ABS	ABS_X, ABS_Y	-256 (Left/Up) ...0... +256 (Right/Down)

Sample code:
evtest.c op_test_inputs.c

Touchscreen

Event interface returns uncalibrated values directly from driver, so you need to use tslib or manage calibration yourself (using data from /etc/pointercal).

Sound

Pandora uses ALSA, but it has OSS emulation enabled too, so GP2X code should work.

Video

Framebuffer device (/dev/fb0) is supported. More to come..

LEDs and backlight

The LEDs can be controlled via /sys/class/leds/, and then a file [1]:

• pandora::sd1
• pandora::sd2
• pandora::charger
• pandora::power
• pandora::bluetooth
• pandora::wifi
• pandora::keypad_bl

Backlight can be controlled via /sys/class/backlight/.

Misc

Some things can be controlled through files in /proc/pandora/:

• /proc/pandora/cpu_mhz_max - if cpufreq is enabled, sets maximum allowed cpu clock, if not, just sets CPU clock to value supplied (echo 600 > /proc/pandora/cpu_mhz_max). Might also just use cpufreq parameters themselves.

more to come..