Accessory Commands and Packets, Packet Processing

ActivMedia Robotics

Normally enabled (default was disabled in P2OS), change E_STALL by sending the AROS command #56. With argument of zero, E_STALL gets disabled. An argument value of one re-enables E_STALL.

ACCESSORY COMMANDS AND PACKETS

Several types of alternative server information packets (SIPs) come with AROS to better support the ActivMedia Robotics community. On request from the client by a related AROS command, the AROS server packages and sends one or a continuous stream of information packets to the client over the HOST serial communication line. Extended packets get sent immediately after the standard SIP that AROS sends to your client every SIP milliseconds (typically 100).22

The standard SIP takes priority and gets sent as soon as the communication port is free and the cycle timer expires. So you may have to adjust the communications baud rate to accommodate all data packets in the allotted cycle time, or some packets may never get sent.

Packet Processing

Identical with the standard SIP, all AROS server information packets get encapsulated with a header (0xFA, 0xFB), byte count, packet type byte, and trailing checksum. It is up to the client to parse the packets, sorted by type for content. Please consult the respective client application programming manuals for details.

ARIA, for example, comes with a framework for packet parsing and has an internal parser for the PSOS/P2OS/AROS packet type 0x3S (S=0-2; aka “standard” SIP), as well as for some of the extended packets we describe in this section.

Table 8. CONFIGpac contents (AROS v1.5 and later)

LABEL	DATA	DESCRIPTION
HEADER	int	Common packet header = 0xfAFB
TYPE	byte	IDs ENCODERpac = 0x20
BYTE COUNT	byte	Number of following data bytes
ROBOT TYPE	str	Typically “Pioneer”
SUBTYPE	str	Identifies the ActivMedia robot model; e.g. “p3dx”,
SERIALNUM	str	Serial number for the robot.
4MOTS	byte	Antiquated (=1 if AT with P2OS)
ROTVELTOP	int	Maximum	rotational velocity; deg/sec
TRANSVELTOP	int	Maximum	translation speed; mm/sec
ROTACCTOP	int	Maximum	rotation (de)acceleration; deg/sec2
TRANSACCTOP	int	Maximum	translational (de)acceleration; mm/sec2
PWMMAX	int	Maximum	motor PWM (500=fully on).
NAME	str	Unique name given to your robot.
SIP	byte	Server information packet cycle time
HOSTBAUD	byte	Baud rate for client-server HOST serial: 0=9.6k, 1=19.2k,
		2=38.4k,	3=56.8k, 4=115.2k.
AUXBAUD	byte	Baud rate for AUX serial port 1; see HostBaud
GRIPPER	int	0 if no	Gripper; else 1
FRONT SONAR	int	1 if robot has front sonar array enabled, else 0
REAR SONAR	byte	1 if robot has rear sonar enabled, else 0
LOWBATTERY	int	In 1/10	volts; alarm activated when battery charge falls
		below this value.
REVCOUNT	int	Current	number of differential encoder ticks for a 360
		degree revolution of the robot.
WATCHDOG	int	Ms time	before robot automatically stops if it has not

22You may have to adjust the HOST serial baud rate to accommodate the additional communications traffic.