Difference between revisions of "GPIO Pins"

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(Added GPIO page and classic GPIO descriptions)
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Revision as of 04:40, 18 July 2015

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.

Section registers

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

Bit/section number to GPIO pin
7 6 5 4 3 2 1 0
Section 0 7 6 5 4 3 2 1 0
Section 1 15 14 13 12 11 10 9 8
Section 2 23 22 21 20 19 18 17 16
Section 3 31 30 29 28 27 26 25 24


Classic CX
0
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
3 I2C data - for communicating with the Touchpad (see Keypads#Touchpad I²C for details)
4
5
6
7
8 Input bit is 0 if Reset Button is pressed
9
10
11
12
13
14
15
16
17
18
19 Input is 0 if WLAN Cradle attached
20
21
22
23 Called LCD_OFF in diags mode
24 Input bit is 1 if a keypad is not plugged in
25
26
27
28
29
30
31
  • GPIO 1 (Section 0, bit 1): Touchpad "clock"
  • GPIO 2 (Section 0, bit 2): Input bit is 0 if battery door open, 1 if closed (TI-Nspire CAS)
  • GPIO 3 (Section 0, bit 3): Touchpad data
  • GPIO 8 (Section 1, bit 0): Input bit is 0 if Reset Button is pressed.
  • GPIO 19 (Section 2, bit 3): Input is 0 if WLAN Cradle attached
  • GPIO 23 (Section 2, bit 7): Called LCD_OFF in diags mode
  • GPIO 24 (Section 3, bit 0): Input bit is 1 if a keypad is not plugged in. (TI-Nspire non-CAS only?)