[riot-notifications] [RIOT-OS/RIOT] i2c_read_regs / i2c_write_regs and endianess (#11544)

Kees Bakker notifications at github.com
Mon May 20 22:25:24 CEST 2019


> In my case the device is an ST EEPROM model M24C64, you can find the datasheet [here](https://www.st.com/resource/en/datasheet/m24c64-f.pdf). The datasheet indeed is not so very explicit about ordering, but it mentions in 5.1 first the most significant address byte. Indeed by using it the other way around then I get into wraparound problems as mentioned.

The datasheet is not very clear. OK, you proved with trial and error that the register address must be send big endian.

> 
> One more similar chip I found from Microchip, [datasheet here](http://ww1.microchip.com/downloads/en/DeviceDoc/21754M.pdf) also uses the most significant byte first and here it's explicitly seen in figure 6-1.

That datasheet is really clear about it, memory address must be send big endian.

Still, I couldn't find any I2C documentation that formally describes this big endian behaviour. But let me quickly add that I'm no I2C expert.

Have you already thought about a PR?

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