Reading multiple bytes using I2C in U-Boot

Question

I am having a problem with the I2C driver for a Freescale p1022tw board. There is a command on U-Boot's console to read from an I2C device:

i2c md chip address[.0, .1, .2] [# of objects]

When I read 4 bytes from a device with id 0x60, at address 0x0, I get:

tw=>i2c md 60 0 4
0000: 45 45 45 45    EEEE

These values that it returned are wrong. I can get the right values if I read one byte at the time:

tw=>i2c md 60 0 1
0000: 45    E
tw=>i2c md 60 1 1
0001: 45    E
tw=>i2c md 60 2 1
0002: 46    F
tw=>i2c md 60 3 1
0003: 00    .

I should have gotten 45 45 46 00 or EEF0 in the first command. In multiple readings for this device, it is returning always just the first byte value. If I try to get 6 bytes starting at address 0x2, this is the output:

tw=>i2c md 60 2 6
0002: 46 46 46 46 46 46    FFFFFF

This problem does not happen on other devices on the bus. For instance, in the device with id 0x4F, the right values are printed:

tw=>i2c md 4F 0.2 6
0000: 18 00 f6 48 00 00    ...H..

The address in the previous command has a ".2" because the chip uses 2 bytes for addresses. The first device only uses 1, so there's no need to put a ".1" (I already tested that).

I went through the implementation of the Freescale driver for the I2C communication, but I didn't change anything on it and it works for other devices. My coworker also says that the very same code works on his board. Have anybody had a similar issue or has any theory about why this is happening?

Thanks in advance.

Answer 1

I met such a situation. I had driver, read and write functions, and it worked not for all i2c devices. I found that was caused the not working device had different operating format for a number of operation. Unfortunately this happens, there a kind of not standard protocols. When you open the doc for the problem device and compare it to working and/or to the driver implementation you most likely will see a difference.