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I2C interface problem with OmniVision OV7670

DISCUSSION Darius 1 participant 2 messages May 14, 2008 Media (V4L/DVB)

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Darius

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#0 lore raw

Hi,

OV7670 does not support repeated start.
When sending several messages (read or write) in one transaction, repeated start is not accepted by OV7670. OV7670 thinks, that it is next clock pulse, not repeated start and second message is not acknowledged. It is known bug of OV7670 or my i2c adapter driver works not correct?
When sending one byte, everything is ok.
It is interesting, how works OV7670 driver, written by Jonathan Corbet?
Because there are used i2c_smbus_write_byte_data() and i2c_smbus_read_byte_data() functions, which means, that in one transaction two messages are sent - register address (write) and read data. For me this does not work, only register address is acknowledged by OV7670, and second message (read data) fails.

I want to know, is there possibility to use multi-message transactions or not?

BR,
Darius

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author
#1 lore raw

btw, I got confirmation from OmniVision - OV7670 does not support multiple I2C commands.

Quoted 10 lines

Hi,

OV7670 does not support repeated start.
When sending several messages (read or write) in one transaction, repeated start is not accepted by OV7670. OV7670 thinks, that it is next clock pulse, not repeated start and second message is not acknowledged. It is known bug of OV7670 or my i2c adapter driver works not correct?
When sending one byte, everything is ok.
It is interesting, how works OV7670 driver, written by Jonathan Corbet?
Because there are used i2c_smbus_write_byte_data() and i2c_smbus_read_byte_data() functions, which means, that in one transaction two messages are sent - register address (write) and read data. For me this does not work, only register address is acknowledged by OV7670, and second message (read data) fails.

Quoted 4 lines

I want to know, is there possibility to use multi-message transactions or not?

BR,
Darius

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