SCCB Control ov7670 Introduction

Ext.: http://archive.cnblogs.com/a/2011464/

Measured a few of the OV7670 SCCB (in fact, is i²c) read and write waveform (digital mode), anyway, can not be wasted, in order to remember, for later reference.

1. Several basic concepts a) in the data transmission phase, SDA changes only when the sck is low, if the sck high level when there is SDA change, it may indicate the start of the I²c or STOPB) Start: When the sck is high, SDA from high jump to low startc of the I²c bus) Stop: When Sck is high, SDA from low jump to high for bus stopd) ACK: After each transmission of 8 bit, the receiver will have a response, if the ACK is low, indicating OK, if the high represents the Nack, But does not indicate that there is a problem, such as master to receive slave data in the process do not want to receive, you can send Nacke address: In the addressing segment, in the 7-bit format address, the 8-bit data sent the first seven bits of the address, such as in the 0x42, The last one said the launch was read or write, read high, write low level. F) Sub-address subaddress: This thing in the specification of the i²c is actually not, but many manufacturers like the whole, in fact, the address section after one or two of their own data (generally use write r/w=0). For example, our previous BB does not have this probability, now the new BB has this concept, but also support 8-bit and 16-bit.

1. A Write Time series

Below is a write address segment, add two data segment waveform, first send chip id,0x42 and r/w=0, then send two write data: 0x32,0xb6.

1. One to write and one to read

Write an address segment first, 0x42, and then write (rw=0) subaddress 0x0B. Then restart the transmission, send the address segment, 0x42, read the value of the subaddress in the previous write, read the value of 0x76, because master at this time receiver, to terminate the transmission, so the master to Salve response to Nack. That is, a 2-phase write plus a 2-phase read in the SCCB specification.

4. Finally, there is no device on the bus waveform, the pull is very weak

SCCB Control ov7670 Introduction