I2C Expansion Board

[pineadmin]

On the second I2c Port (TWI-SDA and TWI-SCL), which is connected to the Pin 28 & 29 of Pi-2 Connector, is on port PL8 and PL9 of the MCU. The base address of the MCU I/O configuration register for this Port L  is on 0x01F02C00. To enable the I2c function for this pin, we need to configure the PL Configuration Register 1(by default, the MCU disable the i/O function of this 2 pin during power up). The detail of the setting can be found at the MCU User Manual on page 410 to page 416.

I think (some one please correct me if I am wrong) all this setting has to be done in the linux kernel in order for the user land program to be able to access it. Since I am not very good in linux kernal, may be someone which is good in it can help out. Thanks.

Regards,
KH Goh

hello khgoh,
i also add my thank you for your work on this issue. i appreciate it. i would like to know if it will be possible in the future , once the kernel issue is resolved, to have both banks [ports] of I2C enabled at same time or if it would be a situation of one or the other at any given time?  also, a more general question since this is first time i have had multiple connections to this extent, will these connections be hot-plugable while power on state? what i mean is can i unplug any given connection and plug in something else, like a usb port allows me to do, while the power is on? of course proper care given to handling is understood. thanks again.

Hi,
For the program that enable the internal pull up on the I2c pin, I already enable the pull up for both of the I2c port. Once the kernel part is resolved, running the program will also turn on the internal pull for the 2nd I2c port.

As for hot plugging the I2c device, on the hardware side, all the i2c pin on the POT board and also on the sensor board already build with spike protector to protect the IC during hot plug. So, as far as the hardware concer, It should be no problem for the hardware to connect the device while power on. 

But on the software application side, your application must also support this feature.

Regards,
KH Goh