Carrol Touch TouchSystems CarrollTouch Prog, Programmer'S Manual

Page: 72 / 274

CARROLL TOUCH Chapter 5 - Smart-Frame Protocol II
Touch System Programmer’s Guide 5-15
The touch system responds with the following report:
E0 06 FE 20 01 86 04 03 FF
FE
is the Cmderr parameter and indicates that a byte count mismatch
error occurred.
20
is the ReportNumber parameter, and the following
four bytes echo the parameters that the touch system received.
As a second example, suppose the touch system has an input buffer size
of 32 bytes and the host sends the following, lengthy, incorrect
command:
66 50 FA 01 02 03 ... 4F FF
The touch system reads bytes until its input buffer overflows, then
responds with the following report:
E0 06 FE FA 01 02 03 ... 1D FF
FE
is the Cmderr parameter and indicates that a byte count mismatch
error occurred. The following 30 bytes echo the command number and
parameters that the touch system received before the input buffer
overflowed.
For a complex example, suppose the touch system has an input buffer
size of 32 bytes and the host sends the command as follows:
66 04 20 01 04 03 FF
Due to noise on the serial line, the touch system actually receives a
value of 40H (64 decimal) for the byte count instead of 04H as follows:
66 40 20 01 04 03 FF
The touch system reads all seven bytes of the command and places
them in its input buffer. No report is sent because the touch system is
expecting a command that is 64 bytes in length (not counting the
header, byte count and trailer), but only 5 of the 64 bytes have arrived
(the command number, the three parameter bytes, and the trailer, which
the touch system interprets as byte 5 of the 64 bytes that it expects to
receive).
The host can then wait until the command completion timeout time of
one second has elapsed, and then re-send the command. The seven
bytes contained in the command are interpreted by the touch system as
bytes 6 through 12 of the 64 bytes that it is expecting, and it again sends