i2c problem: incomplete xfer (0x20) [RESOLVED]

[megamax]

Hi,
I bought a A10s board, a MOD-RTC and a MOD-RS485-ISO but I can't use these modules because every time I try use the i2c bus I get this error: "incomplete xfer (0x20)"
I tried with mod-rs485-iso and MOD-RTC.py in the examples pages and finally i2c-tools, but I ever get this error.
I'm using Debian from uSD.

What I can check? And what means this error?

Thanks!

[megamax]

Resolved:

• for MOD-RTC I added "i2c=2" option in MOD-RTC.py and it works
• for MOD-RS485-ISO I programmed the latest firmware in the module

I hope will be useful to others