Specifications

Remote Control and Receiver-Transceiver Specifications and Requirements
for Windows Media Center in Windows Operating Systems
104
To simplify matters, the following values should be returned.
Status
VRH
VRL
VDH
VDL
Emitter
connected
0x00
0x00
0x00
0x00
Emitter not
connected
0x00
0x00
0xFF
0x00
RSP_EQIRRXCFCNT – Respond with Received Carrier Count
Information
Message ID: RSP_EQIRRXCFCNT
Message length: 4 bytes
Message direction: Device to host
Offset
Name
Value
Description
0
RSP_PORT_IR
0x9F
IR response
1
RSP_EQIRRXCFCN
T
0x15
Response ID – respond with
received carrier count information
2
CH
Number
Carrier count high byte
3
CL
Number
Carrier count low byte
Description
After a time-out of reception on the learning receiver, this response is sent to tell the host the
carrier frequency of the previous sample. The CH and CL values form a 16-bit value that
specifies the count of cycles of the carrier. Carrier count can also be thought of as the number of
leading edges in the previous sample.
This is used by the host to calculate carrier frequency as follows:
int lastCarrierCount = ch*256+cl;
double carrier = ((double)lastCarrierCount) / irPacketOnDuration);
In this example, lastCarrierCount is computed by the host based on the values returned in this
response. irPacketOnDuration value is the total amount of time that the envelope for the signal
was high. This value is computed by the host and is implied by the shape of the RLC envelope
returned from the device since the last RSP_EQIRRXCFCNT response.
This response is unsolicited. It is returned by the receiver when IR arrives but is never explicitly
requested.
The carrier count is a count of pulses that occurred since the last time-out.
RSP_EQIRNUMPORTS – Respond with Number of Ports
Message ID: RSP_EQIRNUMPORTS