4 切換協議的實現方案

在切換之前，禁用解串器輸出，防止系統進入錯誤處理或失效防護模式。不建議在正傳輸數據時在攝像頭之間切換。在通道間進行多路復用時，實現以下協議。

Analog LaunchPad Program
# Digital reset at initialization 
        board.WriteI2C(desAddr,0x01,0x01) 

# Enable CSI-2 output and forwarding (steps below)
        board.WriteI2C(desAddr,0x32,0x01) # Select CSI-2 port 0
        board.WriteI2C(desAddr,0x33,0x03) # Enable CSI-2 output with continuous clock mode
        board.WriteI2C(desAddr,0x20,0x00) # Forward all CSI-2 to port 0

# Before switching the MUX, disable the associated port and forwarding
        board.WriteI2C(desAddr,0x20,0xF0) # Disable forwarding
        board.WriteI2C(desAddr,0x0C,0x00) # Disable the RX port receiver

# After switching the MUX, restart the forwarding and the port receiver. 
        board.WriteI2C(desAddr,0x0C,0x0F) # Enable the RX port receiver 
        time.sleep(0.1) # Allow time for the port to re-lock
        board.WriteI2C(desAddr,0x20,0x00) # Enable forwarding

# The switching protocol above disables forwarding for all channels. Depending on the application, deactivating only the multiplexed channel is sufficient.

For Example:
        # Disable forwarding of RX Port 2
        board.WriteI2C(desAddr, 0x20, 0x40) 

        # Disable Port 2 Receiver
        board.WriteI2C(desAddr, 0x0C, 0x0B)

圖 4-1 展示了從打開多路復用器到重新建立鏈路的切換時間。除重新建立鏈路所需的時間外，還需要考慮通過 I2C 的成像器的初始化時間，攝像頭初始化完成后，就可以在處理器上看到輸出。

藍色：鏈路狀態，綠色：多路復用器打開或關閉

圖 4-1 多路復用期間的鏈路狀態