The Image Sensor Interface (ISI) connects a CMOS-type image sensor to the processor and provides image capture in various formats. The ISI performs data conversion, if necessary, before the storage in memory through DMA.
The ISI supports color CMOS image sensor and grayscale image sensors with a reduced set of functionalities.
In Grayscale mode, the data stream is stored in memory without any processing and so is not compatible with the LCD controller.
Internal FIFOs on the preview and codec paths are used to store the incoming data. The RGB output on the preview path is compatible with the LCD controller. This module outputs the data in RGB format (LCD compatible) and has scaling capabilities to make it compliant to the LCD display resolution (see the table RGB Format in Default Mode, RGB_CFG = 00, No Swap).
Several input formats such as preprocessed RGB or YCbCr are supported through the data bus interface.
The ISI supports two synchronization modes:
- Hardware with ISI_VSYNC and ISI_HSYNC signals
- International Telecommunication Union Recommendation ITU-R BT.656-4 Start-of-Active-Video (SAV) and End-of-Active-Video (EAV) synchronization sequence
Using EAV/SAV for synchronization reduces the pin count (ISI_VSYNC, ISI_HSYNC not used). The polarity of the synchronization pulse is programmable to comply with the sensor signals.
| Signal | Direction | Description |
|---|---|---|
| ISI_VSYNC | In | Vertical Synchronization |
| ISI_HSYNC | In | Horizontal Synchronization |
| ISI_DATA[11..0] | In | Sensor Pixel Data |
| ISI_MCK | Out | Master Clock provided to the Image Sensor. Refer to “Clocks”. |
| ISI_PCK | In | Pixel Clock provided by the Image Sensor |
