iRobot CREATE - OPEN INTERFACE Manual page 21

Song Number Packet ID: 36
The currently selected OI song is returned.
Range: 0-15
Song Playing Packet ID: 37
The state of the OI song player is returned. 1 = OI song
currently playing; 0 = OI song not playing.
Range: 0-1
Number of Stream Packets
The number of data stream packets is returned.
Range: 0-43
Requested Velocity Packet ID: 39
The velocity most recently requested with a Drive command
is returned as a signed 16-bit number, high byte first.
Range: -500 - 500 mm/s
Requested Radius Packet ID: 40
The radius most recently requested with a Drive command
is returned as a signed 16-bit number, high byte first.
Range: -32768 - 32767 mm
Requested Right Velocity
The right wheel velocity most recently requested with a Drive
Direct command is returned as a signed 16-bit number,
high byte first.
Range: -500 - 500 mm/s
Requested Left Velocity
The left wheel velocity most recently requested with a Drive
Direct command is returned as a signed 16-bit number,
high byte first.
Range: -500 - 500 mm/s
iRobot Create Open Interface (OI) Specification
Data Bytes: 1
unsigned
Data Bytes: 1
unsigned
Packet ID: 38 Data Bytes: 1
unsigned
Data Bytes: 
Data Bytes: 
Packet ID: 41 Data Bytes: 
Packet ID: 4 Data Bytes: 
signed
signed
signed
signed
1