This section describes the GPIO interface and known GPIO pins.
Memory Mapped I/O registers
The GPIO registers are separated into sections:
- Section 0: 90000000-9000003F
- Section 1: 90000040-9000007F
- Section 2: 90000080-900000BF
- Section 3: 900000C0-900000FF
- Section 5: 90000140-9000017F
Each register is a word, and only bits 0-7 of each are used. There can be up to 40 devices accessed by this setup, each known as a GPIO. Each GPIO is defined by one of the 8 bits in one of the sections. The number of the GPIO is the section number times 8 plus the bit number. Each GPIO has a status bit and can cause interrupts.
The following addresses are offsets from the beginning of the GPIO section:
- +00 (R): Masked interrupt status ([+04] & [+08])
- +04 (R): Reads raw interrupt status (directly dependent on the GPIO input) or sticky interrupt status (becomes set when GPIO status changes) depending on bit in [+20]
- +04 (W): Write 1 to the bit to reset the sticky interrupt status.
- +08 (R): Reads current interrupt mask bit.
- +08 (W): Write 1 to the bit to enable interrupt (set mask bit to 1)
- +0C (W): Write 1 to the bit to disable interrupt (set mask bit to 0)
The following addresses should be changed with a read-modify-write pattern so as to not disturb other bits in the register.
- +10 (R/W): Direction (set bit to 0 for output, 1 for input)
- +14 (R/W): GPIO output bit
- +18 (R): Reads GPIO input bit.
- +1C (R/W): Setting bit to 1 will invert raw interrupt status (?)
- +20 (R/W): Setting bit to 1 will use sticky interrupt status in [+04], or setting to 0 will use raw interrupt status.
- +24 (R/W): (?)
Currently known pins
|1||I2C clock - for communicating with the Touchpad (see Keypads#Touchpad I²C for details)|
|2||Input bit is 0 if battery door open, 1 if closed||Active low - controls USB VBUS 5V output|
|3||I2C data - for communicating with the Touchpad (see Keypads#Touchpad I²C for details)|
|5||Active low - controls USB VBUS 5V output|
|6||Active low - probably controls charging from USB.|
|8||Input bit is 0 if Reset Button is pressed|
|19||Input is 0 if WLAN Cradle attached|
|20||High if USB micro B plug attached|
|23||Called LCD_OFF in diags mode|
|24||Input bit is 1 if a keypad is not plugged in|