3M C3266PW - Receiving Responses from the Controller

42 3M™ Multi-Touch Chassis Display User Guide
3M Touch Systems, Inc. Proprietary Information – TSD-39373B
Receiving Responses from the Controller
After executing a command, the controller returns a response or acknowledgment to the
host system. Each controller response consists of a header, the command response, and a
terminator in the following format:
<Header>Command Response<Terminator>
Note: The following descriptions of header, response, and terminator, use 3M Touch
Systems terminal emulator key sequences. The format of controller responses varies
depending on the terminal emulation mode you are using.
The header is the first character in the response string and is the ASCII start-of-header
control character SOH. The hexadecimal code for the ASCII SOH control character is 01.
If you are working with an IBM PC compatible system in terminal mode, the SOH
control character returns a ☺ character to the sensor.
The command response, which always follows the header, is a range of ASCII characters
depending on the type of command sent. Responses can be in many forms. For example,
one standard response is 0 (ASCII character ‘zero’ or 30 hexadecimal). This response
indicates a successful command completion for most commands, while it indicates a
failed completion for other commands. Refer to the firmware command section for a
description of what the response indicates for each particular command.
Another standard response is 1 (ASCII character ‘one’ or 31 hexadecimal). In most cases,
this response indicates the command failed. The controller received an invalid command
that it could not execute.
Some possible reasons for a command failure include:
• The command was not formatted correctly.
• The system parameters were not set up to allow command execution.
• The controller does not support the command.
The terminator is the last character of each response string and is an ASCII carriage
return CR. The hexadecimal code for the ASCII CR control character is 0D hexadecimal.
The value returned in the response will be the ASCII control character for a carriage
return, displayed on the screen as the cursor moving to the next line.
In this appendix, responses are shown as a string of ASCII characters consisting of a
header, the response, and a terminator as follows:
<SOH>Response<CR>
Controller Initialization
To initialize the 3M™ PX serial controller for new development, 3M Touch Systems
recommends that the host system issue a Reset command whenever the host system is
powered on and is attempting to establish communication with the controller.