[clug] HWR question

[Bob Edwards]

On 01/03/15 15:18, Eyal Lebedinsky wrote:
> So I am looking at interfacing a 3.3v mcu to a 5v device (over i2c). I
> look on aliexpress for a small
> converter and see a few. One 8 channel device is
>          http://www.aliexpress.com/item/-/32238089139.html
> looks interesting, but when I examine the provided images I notice this one
>
> http://i01.i.aliimg.com/wsphoto/v0/32238089139_6/8CH-IIC-I2C-Logic-Level-Converter-Bi-Directional-Module-DC-DC-5V-to-3-3V-Setp.jpg
>
>
> Am I misreading it or is there no conversion on the 8 data lines (just
> resistors)?
>
> TIA
>

Yep - I2C is "open-drain" (or pull-down only), so the drivers only need
to pull the SCL and SDA lines to GND and don't really care how high they
go when not being pulled (within reason). So a simple low-value inline
resistor on each line is all that you should need - you would probably
get by without them.

cheers,

Bob Edwards.