Hi!

If I understood it correctly, then the current carambola kernel doesn't make use of the I2C peripheral on the RT3050 but instead implements the bit-banging I2C driver using GPIOs, right?

My application requires to periodically read gyro, accelerometer and compass data (from a Sparkfun SEN-10724 sensor stick) with at least 100 Hz. So the GPIO I2C driver will be very slow and consumes a lot of CPU cycles. So I thought I could implement a "true" I2C driver that uses the actual I2C peripheral but as per data sheet, it appears that the I2C peripheral is not connected to the interrupt controller - so it's not possible to create an I2C interrupt handler. I only found a very old version of the data sheet from 2008 (I have seen references to a newer one from 2009) - maybe the data sheet is just missing the appropriate information?

In the mean time, I just mapped the I2C register to user space and created a simple "user space I2C driver" (attached). It can either poll for the completion of an I2C operation or it uses nanosleep() to wait in between bytes. It still sucks a lot of CPU cycles (as a true interrupt driven driver would also do it), but at least it's possible to read the sensor at a rate of 500Hz (I'd prefer 1000 Hz, but >100Hz is probably good enough for me).

regards

Bernhard