3M Touch Screen Controller EX 111, Reference Manual

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3M™ MicroTouch™ Controller EX USB Reference Guide 27
3M Touch Systems, Inc. Proprietary Information -- 29489v05
Read Parameter Request 16
This is a request to send the contents of a parameter via the control endpoint. This is a
one-time transfer of data. The request is used to access data in the controller.
This request provides a means for reading the configuration parameters. The request uses
parameter numbers to determine what data is being requested and where that data is
located.
Table 18. Read Parameter Request
Offset Field Size Value Description
0 bmRequestType 1 11000000 Characteristics
1 bRequest 1 16 Command number
2 wValue 2 0xXXXX Parameter number
4 wIndex 2 0x0000 Not used
6 wLength 2 0xXXXX Length of Parameter Data report
The direction bit in bmRequestType has been set to 1 (device-to-host) to return the
contents of the requested parameter.
The byte bRequest is set to 16 to indicate that this is the Read Parameter request.
The wValue field is set to the number of the parameter being requested.
This request does not use the wIndex field. This field should be set to zero to ensure
future compatibility.
The wLength field is the number of bytes being sent by the device to the host. The data is
returned to the host in the format of the Parameter Data report, which has a 3-byte header,
so 3 must be added to the number of parameter bytes desired. The following table lists
the parameters currently supported and the appropriate settings for the request fields.
Table 19. Supported Parameters
Parameter
(wValue)
wIndex
wLength
(bytes+3)
Range Description
0 0 0 0 Reserved for future use
1 0 5 0 – 3 Sensor orientation - where the lower left
corner of the display maps to the sensor.
0000 – Upper right
0001 – Lower right
0002 – Upper left
0003 – Lower left (standard, not rotated)
2 0 7 0 – 2
32
-1 Controller serial number