User's Manual

Last change:
Dec 23, 2016
Torch Bigtide Digital Technology Co., Ltd.
Page 15 of 32
3.OPERATING GUIDE
3.1 Operation display methods
The display no physical buttons. The host uses the DDC/CI command to set the display
through the DP connector.
3.2 DDC/CI Communication Command
Requests from host to display use the following message structure:
 Destination: 0x6E – standard display slave address for writing
 Source: 0x51 – standard host address
 Length: 0x80 + number of bytes following this byte, not including checksum.
 Command: 0xC0 – the first command from vendor-specific range
 Request code: 1, 2 or 3 bytes specifying an action or a data read (starts with 0xBB )/write (starts
with 0xBC) directive.
 Optional data payload for action or write directives: Legacy format uses ASCII representation of
numbers (e.g. 0x31 as “1”), but we would like to use little-endian binary values for new directives.
 Checksum byte: XOR of all preceding bytes
Responses to read directive use the following message structure
 Destination: 0x6F – standard display slave address for reading
 Source: 0x51 – standard host address
 Length: 0x80 + number of bytes following this byte, not including checksum.
 Command: 0xC1 – the second command from vendor-specific range
 Reply data. Legacy format uses ASCII character representation of numbers (e.g. 0x31 is ‘1’), but we
would like to use little-endian binary values for new directives.
 Checksum byte: XOR of all preceding bytes
Communication is always initiated by a host. There is never a reply to an action or write request. Response
messages do not include a code of the read request that prompted it. Here is a list of request codes
grouped into use cases.
1. Identification requests
a. 0xBB 0x53 – return GE OEC Part Number as ASCII string in 5XXXXXX-YY format. This part number
will be on monitor drawings. Two numbers after dash will change for any revision and should be
updated. This request is also used to probe i2c channels to find which one is connected to a
monitor, because Linux assigns devices inconsistently.
b. 0xBB 0x52 – return a serial number as ASCII string in arbitrary format. Needs to be unique and
cross referenced to production documentation.
c. 0xBB 0x02 0x00 – return internal version as ASCII string in arbitrary format. Should include
firmware version (suggested major.minor) format, FPGA and board revisions. Needs to change for
any production modification, even if functionally equivalent and does not require dash number
updates.
2. Diagnostic requests
a. 0xBB 0x01 – return video display status. 0x31 (‘1’) means live video stream is being received and
displayed. 0x30 (‘0’) means something wrong with video stream, but I2C communications must be
still OK to get a reply