RTL8231 GPIO expander
The RTL8231 IC is a companion chip often used with RTL83xx SoCs to extend the number of available GPIOs or LED outputs. It can be controlled via SMI (I2C-like), MIIM, or as a shift register. It comes in an LQFP-48 package:
|36 25|
- +----------+ -
37 | | 24
| RTL8231 |
48 | o | 13
- +----------+ -
|1 12|
Strapping pins
| Number | Name | Description |
|---|---|---|
| 15 | SMI_DIS | Disable SMI/MIIM mode and run in shift-register mode if pulled high. |
| 42 | MOD[0] | SMI/MIIM mode: pull high to run in MIIM mode, pull low for SMI (I2C) mode. |
| 37 | ADDR[0] | MIIM mode: ADDR[4:0] indicates the device address SMI mode: ADDR[2:0] indicates the three lowest bits of the device address. If ADDR[3] is pulled low, 8-bit register addresses are used, if it is pulled high 16-bit wide registers addresses are used. |
| 38 | ADDR[1] | |
| 39 | ADDR[2] | |
| 40 | ADDR[3] | |
| 41 | ADDR[4] |