RaspberryPI I2C confilct problem
The problem of I2C conflict between VEYE MIPI CSI-2 camera module and MIPI DSI-2 LCD screen on Raspberry Pi
1 Problem description
On Raspberry Pi 3B, 3B+, 4B and CM4, MIPI CSI-2 and DSI-2 use the same I2C bus (VC-I2C). In the hardware schematic, the pins are short-circuited.
Please refer to Schematics for the various Raspberry Pi board versions for more details.
In general, in the Raspberry Pi main chip(BCM chip), the VC-I2C is controlled by GPU and cannot be accessed by CPU. The GPU of Raspberry Pi is not open, while the programs on the CPU side are open source.
To be able to use this I2C interface on CPU, we use the camera_i2c_config script to expose VC-I2C to CPU which creates a problem:
When using our CSI-2 camera module and screen of the DSI-2 interface at the same time, CPU controls the camera module through VC-I2C as the master, and GPUcontrols the LCD screen through VC-I2C as the master too. There is a certain probability that there will be I2C access conflicts, which will lead to possible I2C miscodes and misconfigurations.
2 Solution
2.1 Hardware solution (recommended)
In order to avoid conflicts, when you need to use our MIPI camera module and LCD screen in the product at the same time, it is recommended to use i2C on 40-pin GPIO header to control the camera.
- VEYE-MIPI-327、CS-MIPI-IMX307、CS-MIPI-SC132
It is recommended to make an adapter board to export the i2c pin of the camera to a separate connector and disconnect it from the Raspberry Pi FFC cable.
- VEYE-MIPI-327S
We have supported the independent I2C interface function, and there is no need to make a separate adapter board.
2.2 Software solution (ways to avoid it)
- For VEYE Series
The collision can be avoided by turning off the i2C response of the camera.
./i2c_write $I2C_DEV $I2C_ADDR 0x07 0xFF
- For CS series
Firmware upgrading...
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If you have a better solution or need to consult, please contact xumm#csoneplus.com.