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NPont
Beginner
1,899 Views

GPIO Pins - I2C IO Expanders

Hi All,

I'm using Edison with kit for Arduino board. I cannot find where are defined/mapped pins as GPIO pins while they are IO Expanders outputs.

For example GPIO243 is the IO1.3 pin of U16 chip (an IO Expander).

Then, in which point kernel is learned to search IO expanders at I2C addresses 0x20, 0x21, 0x22 and 0x23.

Thank you in advance,

Nicola

6 Replies
idata
Community Manager
107 Views

Hello NicolaUB,

 

 

Why do you need this information? Could you please let us know a little bit more about your project?

 

 

Peter.
NPont
Beginner
107 Views

Hi Peter,

I would know this information because if I wanted to use Intel Edison without Arduino board I don't know, for example, how to remove support for these IO expanders or use an IO expander with another I2C address or add GPIOs mapped on IO expander outputs.

Regards,

Nicola

idata
Community Manager
107 Views

I understand, please let me investigate about this. I'll get back to you as soon as possible.

 

 

Peter.
idata
Community Manager
107 Views

Hi Nicola,

 

 

The I2C1 wiring is not exposed on the Arduino board because it is directly connected to the PCAL9555 to provide all of the pin-muxing capabilities. I suggest you to use mini breakout board where you have access to I2C1 and I2C6 through the 70-pin connector.

 

 

Peter.
Andriy_S_Intel
Employee
107 Views

NicolaUB kirjoitti:

Then, in which point kernel is learned to search IO expanders at I2C addresses 0x20, 0x21, 0x22 and 0x23.

The board is SFI (Simple Firmware Interface) enabled, from that the kernel takes DEVS table and parses it.

You may check SFI 0.8.2 specification and dump table from /sys/firmware/sfi/tables/DEVS.

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