Carrol Touch TouchSystems CarrollTouch Prog, Руководство программиста, Страница: 53 / 274

Chapter 4 - Smart-Frame Protocol CARROLL TOUCH
4-12 Touch System Programmer’s Guide
4. Send the Report_Transfer_On (44H) command, followed by the
Get_Error_Report (32H) command.
5. Read the Error Report sent by the touch system. If the report is
received correctly and indicates no errors, the touch system is
ready to use. If the report is not received correctly, or contains
errors, take the appropriate action.
Using an SBC
Touch systems that include the SBC are unique because they use the
CPU of the host PC to manage the scanning of the frame and reporting
of touch coordinates instead of using a dedicated microprocessor.
The following exceptions to the standard Smart-Frame Protocol exist
for SBC-based touch systems:
• The scan reporting method is not supported by the SBC. Sending
the Scan_Reporting (22H) command to the SBC has no effect.
• Sending the Echo_On (20H) command, the Echo_Off (21H)
command, or the Reset (45H) command to the SBC has no effect,
and causes the Invalid Command error to occur.
• The Hardware_Flow_Control_On (41H) and the Hardware_
Flow_Control_Off (42H) commands apply only to touch systems
that communicate serially, and have no effect when sent to the
SBC.
When using an SBC-based touch system, turning touch scanning on via
the Touch_Scanning_On (2AH) command causes the SBC hardware to
begin issuing hardware interrupts. Turning touch scanning off via the
Touch_Scanning_Off (2BH) command causes the SBC hardware to
stop issuing hardware interrupts. Since the SBC TAPI driver only uses
host CPU time when an interrupt is issued by the SBC hardware,
turning touch scanning off whenever possible releases host CPU time
that would otherwise be used by the SBC TAPI driver for other uses.
Compatibility Issues/Programming Tips
An application or driver that is hard-wired to a typical size or model of
CT touch system may require modification if a different touch system
is used. Applications and drivers that use the Smart-Frame Protocol to
interface to the touch system should be designed to work with all types
and sizes of touch systems that use the Smart-Frame Protocol. This lets
you continue to use the application or driver without modification if a
different size and/or model of CT touch system is used. The following
design rules should be followed.