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vid - Motorola 823 video output


bind -b #v /dev



The vid device serves two files giving basic access to the on-chip video output of the Motorola 823. It assumes a video hardware configuration exactly like that of the 823FADS board, with an I²C interface to an off-chip ADV7176 NTSC/PAL converter at I²C address 0x54.

The control device vidctl accepts the following commands:

Disable LCD panel (if present) and enable output from the video frame buffer.
Stop display from the video frame buffer and re-enable the LCD panel (if present).
mode m
Set the video output format to m, which is one of: ntsc, pal-i, pal-m or pal-n. This command is only effective when video output is off. When next switched on, the both the video controller RAM and ADV7176 are reprogrammed to the new format.

Video data can be written to the video frame buffer by writes of the viddata file. The file offset selects the starting byte within the frame buffer. Reads return the corresponding data from the frame buffer. The application is responsible for formatting the data as the 823's video encoder requires, for the selected video format.

The file vidcram gives read and write access to the contents of the video control RAM. The file offset addresses bytes in the RAM; values can be read from or written to the RAM in groups of 4-byte big-endian words.




Square pixel mode cannot be used on the FADS board: no suitable video clock source is available.

vid(3) Rev:  Tue Mar 31 02:42:38 GMT 2015