HP 720 SCP protocolFollowing is the probable specification for the SCP protocol on 720 printers. Thanks to Jim Peterson and Ben Boule for much of this information.
Several of the commands are described below: CS=0x186, CR=1 (INIT_COM ?) This is some sort of initialization command. It probably
initializes the communications channel, since it is always the first
packet sent by the windows driver. It's data consists of 8 bytes
that I have only seen as: 00 00 01 F4 01 00 00 00 CS=0x18F, CR=2 (INIT_DATA ?) This is another initialization command. It is sent once at the
beginning of each file printed, after the INIT_COM packet. It is
preceded by a 4-byte VLink packet sent to channel 0. This suggests
that it somehow initializes the data channel of the printer (thus our
temporary name). This packet typically contains the values: DE AD
BE EF. The data portion of this command usually contains the
following 8 bytes: DE AD BE EF 02 00 00 00 CS=0x183, CR=1 (INIT_PAGE ?) This command is sent each time before a page is loaded. It appears
to set some parameters for the page, possibly the minimum and maximum
horizontal positions for each of the four pens (?). The only data I have
seen it contain is the following: 28 2D 00 41 2D 32 00 46 2D 32 00 46 2D 32 00 46 CS=0x181, CR=1 (HANDLE_MEDIA) This is the command that handles loading and ejecting of pages.
CS=0x180, CR=1 (PRINT_SWEEP) This is the print sweep command. It causes the print head to print a sweep of data (which has previously been sent over channel 0). The PRINT_SWEEP command controls the print head while printing data on a page. It can take on two forms, one when printing with the black nozzles, and one when printing with the color nozzles. The black form is described in the most detail here, since it is what I have devoted the most attention to. Following is the format of the first 48 bytes of data for this command:
Following this header are sets of 16-byte rows to describe how to handle the nozzles. The odd nozzles are described by the first row, and the even nozzles are described by the second row.
|