Communication with Pcam 5c - 16 bit address

[poiuyt]

Hi,

I have a question, I am trying to design my own Zybo Z7-20 Pcam 5C project and I have a problem with the SCCB (I2C like) communication. I am trying to develop my own I2C module in the PL (I don't want to use the PS of the Zybo Z7) but contrary to what the I2C protocol requires, the register adresses of the OV5640 camera are on 16bits (instead of 7bits in I2C protocol). So I don't know how to address the registers. I also have to communicate if the transaction is a read or a write with a R/W bit.

I studied the sdk of the demo Pcam 5C but did not understand how the communication was done. The SCCB Application Note doesn't explain it either.

Does anyone have an idea ?

Thank you for your help

[thinkthinkthink]

It's pretty simple, first you address the Pcam itself (7 bits) and then you send the register address as two bytes of data over I2C, the most significant 8 bits of the register address followed by the least significant 8 bits. 

Edited April 28, 2022 by thinkthinkthink

[poiuyt]

Thank you for your quick response ! Is there an ACK bit between the two bytes ?

And where is the R/W bit ?

Edited April 28, 2022 by poiuyt

[thinkthinkthink]

17 minutes ago, poiuyt said:

Thank you for your quick response ! Is there an ACK bit between the two bytes ?

Absolutely. The sequence should look something like this: Start -> Pcam address 7bits + Write bit -> ACK -> Register Addr High 8 bits -> ACK -> Register Addr Low 8 bits -> ACK -> Write Data 8 bits -> ACK -> Stop.

The above sequence is meant for a Write transaction. For Read transactions you have to first WRITE the register address and then re-address the Pcam but this time ending in Read bit like so:

Start -> Pcam address 7bits + Write bit -> ACK -> Register Addr High 8 bits -> ACK -> Register Addr Low 8 bits -> ACK -> Repeated Start -> Pcam address 7bits + Read bit -> ACK -> Read Data 8 bits -> NACK -> Stop.

Edited April 28, 2022 by thinkthinkthink

[poiuyt]

Thank you. It was finally so simple :D

Have a nice day !