Host <-> Device Communication

Table of Contents

• Overview
• Byte Ordering
• Message Format
  • Request
  • Response
• Commands
  • Echo
    • Request Payload
    • Response Payload
  • Set Mode
    • Request Payload
    • Response Payload
  • Get Hardware Information
    • Request Payload
    • Response Payload
  • Run Self Test
    • Request Payload
    • Response Payload
  • Reset
    • Request Payload
    • Response Payload
  • Get Break Time
    • Request Payload
    • Response Payload
  • Set Break Time
    • Request Payload
    • Response Payload
  • Get Mark Time
    • Request Payload
    • Response Payload
  • Set Mark Time
    • Request Payload
    • Response Payload
  • Get RDM Broadcast Timeout
    • Request Payload
    • Response Payload
  • Set RDM Broadcast Timeout
    • Request Payload
    • Response Payload
  • Get RDM Response Timeout
    • Request Payload
    • Response Payload
  • Set RDM Response Timeout
    • Request Payload
    • Response Payload
  • Get RDM DUB Response Limit
    • Request Payload
    • Response Payload
  • Set RDM DUB Response Limit
    • Request Payload
    • Response Payload
  • Get RDM Responder Delay
    • Request Payload
    • Response Payload
  • Set RDM Responder Delay
    • Request Payload
    • Response Payload
  • Get RDM Responder Jitter
    • Request Payload
    • Response Payload
  • Set RDM Responder Jitter
    • Request Payload
    • Response Payload
  • Transmit DMX512
    • Request Payload
    • Response Payload
  • Transmit RDM DUB
    • Request Payload
    • Response Payload
  • Transmit Broadcast RDM Get / Set
    • Request Payload
    • Response Payload
  • Transmit RDM Get / Set
    • Request Payload
    • Response Payload
  • Unrecognised Commands
• Transport Considerations
  • USB

Overview

The Host and Device communicate by exchanging messages. Each message represents an operation or command. All communication is initiated by the Host and the Device sends a single message in reply to each command.

Messages sent from the Host to the Device are Requests, messages sent from the Device to the Host are Responses.

Byte Ordering

All multi-byte fields are sent little endian (LSB first) unless otherwise specified.

Message Format

Request

Each request message begins with a common header, zero or more byte of payload data, an end-of-message marker and then zero or more bytes of padding. The total message size must not exceed USB_READ_BUFFER_SIZE.

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      SOM      |     Token     |            Command            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |            Length             |       Payload (if any)        \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 /                                                               /
 \                        Payload (if any)                       \
 /                                                               /
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      EOM      |               Padding (optional)              \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

SOM	The start of message identifier: START_OF_MESSAGE_ID
Token	A token for the request. The same token will be returned in the response. Typically the host will increment the token with each request.
Command	The Command identifier.
Length	The length of the data included in the request. The valid range is 0 - 579 bytes.
Payload	The payload data associated with the request. See each command type below for the specific format of the payload data.
EOM	The end of message identifier: END_OF_MESSAGE_ID
Padding	Extra padding. If present this should be filled with 0s. Padding can be added as long as the total message does not exceed USB_READ_BUFFER_SIZE.

Response

Responses use the same header as Requests, with an additional 2 bytes to indicate the return code and status flags.

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      SOM      |     Token     |            Command            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |            Length             |  Return_Code   |     Status   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 /                                                               /
 \                        Payload (if any)                       \
 /                                                               /
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      EOM      |               Padding (optional)              \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

SOM	The start of message identifier: START_OF_MESSAGE_ID
Token	The token that was provided in the corresponding request.
Command	The Command identifier.
Return_Code	The ReturnCode of the response.
Status	The status bitfield.
Length	The length of the data included in the command. The valid range is 0 - 579 bytes.
Payload	The payload data associated with the command. See each command type below for the specific format of the payload data.
EOM	The end of message identifier: END_OF_MESSAGE_ID
Padding	Extra padding. If present this should be filled with 0s. Padding can be added as long as the total message does not exceed USB_READ_BUFFER_SIZE.

Commands

Echo

Echo data back from the device. This serves as a basic test that Host to Device communications are working correctly.

Request Payload

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 \                     Data (variable size)                      \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Data	0 or more bytes of data.

Response Payload

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 \                     Data (variable size)                      \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Data	0 or more bytes of data, to match what was provided in the request.

Returns

RC_OK.

Set Mode

Set the operating mode of the device. The device can operate as either a controller or a responder.

Request Payload

  0
  0 1 2 3 4 5 6 7 8
 +-+-+-+-+-+-+-+-+-+
 |   Mode          |
 +-+-+-+-+-+-+-+-+-+

Parameters

Mode	The new mode to operate in. 0 for controller, 1 for responder.

Response Payload

The response contains no data.

Returns

RC_OK.

Get Hardware Information

Get the hardware information for the device.

Request Payload

The request contains no data.

Response Payload

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |          Model ID               |             UID             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                             UID (cont.)                       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                            MAC Address                        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |       MAC Address (cont.)       |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Model_Id	The JaRuleModel of the device.
UID	The UID of the device, in network byte order.
MAC	The MAC address of the device, in network byte order. If the device does not have a MAC this will be 0.

Returns

RC_OK.

Run Self Test

Run the loopback self test. The device must be in self test mode to perform this.

Request Payload

The request contains no data.

Response Payload

The response contains no data.

Returns

RC_OK or RC_TEST_FAILED.

Reset

Resets the device. This can be used to recover from failures.

Request Payload

The request contains no data.

Response Payload

The response contains no data.

Returns

RC_OK.

Get Break Time

Gets the current break time for outgoing DMX512 / RDM messages.

Request Payload

The request contains no data.

Response Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |          Break_Time           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Break_Time

The current break time in microseconds.

Returns

RC_OK.

Set Break Time

Sets the break time for outgoing DMX512 / RDM messages.

Request Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |           Break_Time          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Break_Time

The new break time in microseconds. See Transceiver_SetBreakTime() for the range of values allowed.

Response Payload

The response contains no data.

Returns

RC_OK or RC_BAD_PARAM if the value was out of range.

Get Mark Time

Gets the current mark-after-break time for outgoing DMX512 / RDM messages.

Request Payload

The request contains no data.

Response Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |         Mark_Time             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Mark_Time

The current mark time in microseconds.

Returns

RC_OK.

Set Mark Time

Sets the mark time for outgoing DMX512 / RDM messages.

Request Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |         Mark_Time             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Mark_Time

The new mark time in microseconds. See Transceiver_SetMarkTime() for the range of values allowed.

Response Payload

The response contains no data.

Returns

RC_OK or RC_BAD_PARAM if the value was out of range.

Get RDM Broadcast Timeout

Get the time the controller will wait for an RDM Response after sending a broadcast command.

Request Payload

The request contains no data.

Response Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |             Timeout           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Timeout

The current RDM broadcast timeout, in 10ths of a millisecond.

Returns

RC_OK.

Set RDM Broadcast Timeout

Sets the time to wait for an RDM response after sending a broadcast RDM command. When set to a non-0 value, this allows us to detect responders that incorrectly respond to broadcast commands.

Request Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |             Timeout           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Timeout

The time to wait for a RDM response after a broadcast command, in 10ths of a millisecond. See Transceiver_SetRDMBroadcastTimeout().

Response Payload

The response contains no data.

Returns

RC_OK or RC_BAD_PARAM if the value was out of range.

Get RDM Response Timeout

Get the time that the controller will wait for an RDM Response after sending an RDM command.

Request Payload

The request contains no data.

Response Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |             Timeout           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Timeout

The current RDM response timeout, in 10ths of a millisecond.

Returns

RC_OK.

Set RDM Response Timeout

Sets the time to wait for a reply after a sending an RDM command.

Request Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |             Timeout           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Timeout

The time to wait for a RDM response after a broadcast command, in 10ths of a millisecond. See Transceiver_SetRDMResponseTimeout().

Response Payload

The response contains no data.

Returns

RC_OK or RC_BAD_PARAM if the value was out of range.

Get RDM DUB Response Limit

Get the maximum time a DUB response can take.

Request Payload

The request contains no data.

Response Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |              Limit            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Limit

The maximum time a DUB response can take, in 10ths of a microsecond.

Returns

RC_OK.

Set RDM DUB Response Limit

Sets the time to wait for a reply after a sending an RDM command.

Request Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |              Limit            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Limit

The maximum time a DUB response can take, in 10ths of a millisecond. See Transceiver_SetRDMDUBResponseLimit().

Response Payload

The response contains no data.

Returns

RC_OK or RC_BAD_PARAM if the value was out of range.

Get RDM Responder Delay

Get the minimum time the responder waits before sending an RDM response.

Request Payload

The request contains no data.

Response Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |              Delay            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Delay

The current RDM responder delay, in 10ths of a microsecond.

Returns

RC_OK.

Set RDM Responder Delay

Sets the minimum time the responder waits before sending an RDM response.

Request Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |              Delay            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Delay

The minimum time to wait before sending an RDM response, in 10ths of a microsecond. See Transceiver_SetRDMResponderDelay().

Response Payload

The response contains no data.

Returns

RC_OK or RC_BAD_PARAM if the value was out of range.

Get RDM Responder Jitter

Get the maximum jitter to use when sending RDM responses.

Request Payload

The request contains no data.

Response Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |              Jitter           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Jitter

The current RDM responder jitter, in 10ths of a microsecond.

Returns

RC_OK.

Set RDM Responder Jitter

Set the jitter to use when sending RDM responses.

Request Payload

  0                   1
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |              Jitter           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Delay

The jitter to use when sending an RDM response, in 10ths of a microsecond. See Transceiver_SetRDMResponderJitter().

Response Payload

The response contains no data.

Returns

RC_OK or RC_BAD_PARAM if the value was out of range.

Transmit DMX512

Sends a single DMX512, Null Start Code frame.

Request Payload

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 \                   DMX_Data (variable size)                    \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

DMX_Data

The DMX512 slot data, excluding the start code. The number of slots may be 0 - 512.

Response Payload

The response contains no data.

Returns

• RC_OK if the frame was sent correctly.
• RC_BUFFER_FULL if the transmit buffer is full.
• RC_TX_ERROR if a transmit error occurred.

Transmit RDM DUB

Sends a RDM discovery unique branch command and then listens for a response. If any data is received, it is returned in the response payload. If no data is received a RC_RDM_TIMEOUT is returned.

The response payload includes timing data.

Request Payload

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 \                          DUB_Command                          \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

DUB_Command

The RDM Discovery Unique Branch command, excluding the start code. The command should be 37 bytes.

Response Payload

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |        Discovery_Start        |        Discovery_End          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 \               RDM_DUB_Response (variable size)                \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Discovery_Start	the time from the end of the transmitted DUB frame to the start of the DUB response, in 10ths of a microsecond. Undefined unless RC_OK was returned.
Discovery_End	the time from the end of the transmitted DUB frame to the end of the DUB response, in 10ths of a microsecond. Undefined unless RC_OK was returned.
RDM_DUB_Response	The raw response, if any was received.

Returns

• RC_OK if the frame was sent correctly and data was received.
• RC_BUFFER_FULL if the transmit buffer is full.
• RC_TX_ERROR if a transmit error occurred.
• RC_RDM_TIMEOUT if no response was received.

Transmit Broadcast RDM Get / Set

Sends a broadcast RDM Get / Set command. If the Broadcast Listen Delay is not 0, the transceiver will then listen for a response. If a response is received, it will be returned in the response payload.

Request Payload

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 \                        RDM_Command                            \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

RDM_Command

The broadcast RDM Get / Set command, excluding the start code.

Response Payload

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |          Break_Start           |           Break_End          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |           Mark_End             | RDM_Response (variable size) \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 \                 RDM_Response (variable size)                  \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Break_Start	the time from the end of the transmitted RDM frame to the start of the break, in 10ths of a microsecond. Undefined unless RC_RDM_BCAST_RESPONSE was returned.
Break_End	the time from the end of the transmitted RDM frame to the end of the break / start of the mark, in 10ths of a microsecond. Undefined unless RC_RDM_BCAST_RESPONSE was returned.
Mark_End	the time from the end of the transmitted RDM frame to the start of the mark, in 10ths of a microsecond. Undefined unless RC_RDM_BCAST_RESPONSE was returned.
RDM_Response	The RDM response, if any was received.

Returns

• RC_OK if the frame was broadcast correctly and the broadcast listen delay was 0 or the delay was non-0 and no data was received.
• RC_BUFFER_FULL if the transmit buffer is full.
• RC_TX_ERROR if a transmit error occurred.
• RC_RDM_BCAST_RESPONSE if a response was received.

Transmit RDM Get / Set

Send a RDM Get / Set command and listen for a response. If a response is received, it will be returned in the response payload.

Request Payload

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 \                        RDM_Command                            \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

RDM_Command

The RDM Get / Set command, excluding the start code.

Response Payload

  0                   1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |          Break_Start           |           Break_End          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |           Mark_End             | RDM_Response (variable size) \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 \                 RDM_Response (variable size)                  \
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Parameters

Break_Start	the time from the end of the transmitted RDM frame to the start of the break, in 10ths of a microsecond. Undefined unless RC_OK was returned.
Break_End	the time from the end of the transmitted RDM frame to the end of the break / start of the mark, in 10ths of a microsecond. Undefined unless RC_OK was returned.
Mark_End	the time from the end of the transmitted RDM frame to the start of the mark, in 10ths of a microsecond. Undefined unless RC_OK was returned.
RDM_Response	The RDM response, if any was received.

Returns

• RC_OK if the frame was sent correctly and a response was received.
• RC_BUFFER_FULL if the transmit buffer is full.
• RC_TX_ERROR if a transmit error occurred.
• RC_RDM_TIMEOUT if no response was received.

Unrecognised Commands

If the device receives a command ID that is doesn't recognize it will return RC_UNKNOWN.

Transport Considerations

USB

Communication with the Ja Rule device happens over a custom endpoint.

The maximum packet size (wMaxPacketSize) for the USB device is 64 bytes. This is the largest packet size for a full speed, bulk endpoint. The RX buffer must be a multiple of the maxPacketSize. Since the largest payload data size is 513 bytes, we'll set the RX buffer size to 640 (64 * 10).

On the Microchip RX side, the USB_DEVICE_EVENT_ENDPOINT_READ_COMPLETE event will be triggered if either:

• the host sends less than maxPacketSize data in any transaction
• the host sends maxPacketSize data, and the total size matches the rx buffer size.

libusb on Linux supports a Zero Length Packet (ZLP) flag, which will automatically send a zero length packet if a transfer ends on a wMaxPacketSize boundary. Other host OS's don't seem to support this, so the host side will need to manually pad the message to trigger the USB_DEVICE_EVENT_ENDPOINT_READ_COMPLETE event.