we're working on a robotics project, and are tryng using an i2c bus to communicate between our microcontrollers and our mini-itx pc (via-embedded Epia ML). the kernel is rather patched to support the hardware, but i think the important bits are untouched (I didn't do the kernel patching myself). It is fairly a recent kernel, i'm pretty sure 2.6.11 (i'd check, but the box is not in front of me atm). We have been trying to write some preliminary testing code to communicate over the i2c bus. some of the original testing code used i2c-dev.h from the lm_sensors project to use the SMBus functions. These seem to work correctly. However, we don't want to use SMBus, as it is more difficult to implement in the microcontrollers. Instead, we would like to use plain i2c. >From my reading of Documentation/i2c/dev-inteface and some of the kernel source, we should be able to open(), then use ioctl() to set the slave address, and finally use read() and write() to make i2c reads and writes. although the dev-interface file seems to be outdated (the i2c_smbus_* "macro's" it refers to are no longer in the kernel headers, and are now only in the lm_sensors' i2c-dev.h), my amateur reading of the kernel source supports that this should work. However, a read call results in errno=ENOSYS (Function not implemented), although on one run, i actually got EPERM, and another time resulted in SEGV. I'm sure we've done something wrong, but I can't figure out what it is, and the ENOSYS mystifies me. I'm fairly sure all necessary kernel modules are loaded (i2c-core, i2c-dev, i2c-viapro, some others...) since i2cdetect works, as well as the test using i2c_smbus_write_block_data(). Thanks, David Sharp CalPoly Robotics Club
