7.30 p2os

Authors

Brian P. Gerkey gerkey(at)stanford.edu,Kasper Støy,James McKenna

Synopsis

Many robots made by ActivMedia, such as the Pioneer series and the AmigoBot, are controlled by a microcontroller that runs a special embedded operating system called P2OS (on older robots it is called PSOS). The host computer talks to the P2OS microcontroller over a standard RS232 serial line. Player includes a driver that offer access to the various P2OS-mediated devices, logically splitting up the devices' functionality.

Interfaces / Configuration requests

Although all the P2OS interaction is actually done in a single thread, the different P2OS devices are accessed through different Player drivers, each supporting a different interface and supporting some subset of configuration requests:

• p2os_aio:
  • Interface: aio (see Section 6.3)
  • Configurations: none
  • Notes: Provides access to analog User I/O.
• p2os_bumper:
  • Interface: bumper (see Section 6.8)
  • Configurations: none
  • Notes: Provides access to Pioneer bumpers, for those robots so equipped.
• p2os_cmucam:
  • Interface: blobfinder (see Section 6.7)
  • Configurations: SET_COLOR, SET_IMAGER_PARAMS
  • Notes: Controls a CMUCam that is connected to the AUX2 port on the P2OS board. Use the SET_COLOR request to tell the camera which color to track.
• p2os_compass:
  • Interface: position (see Section 6.19)
  • Configurations: none
  • Notes: Fills the compass heading into the yaw field of the position data packet. Accepts no commands.
• p2os_dio:
  • Interface: dio (see Section 6.11)
  • Configurations: none
  • Notes: Provides access to digital User I/O.
• p2os_gripper:
  • Interface: gripper (see Section 6.14)
  • Configurations: none
  • Notes: Provides access to a Pioneer gripper, for those robots so equipped.
• p2os_position:
  • Interface: position (see Section 6.19)
  • Configurations: GET_GEOM, MOTOR_POWER, VELOCITY_MODE, RESET_ODOM
  • Notes: Provides access to a differential wheelbase. Only speed control is supported.
• p2os_power:
  • Interface: power (see Section 6.21)
  • Configurations: none
  • Notes: Provides access to battery charge information.
• p2os_sonar:
  • Interface: sonar (see Section 6.23)
  • Configurations: GET_GEOM, POWER
  • Notes: Provides access to a sonar array. Sonar indices start with 0 at the front left and increase clockwise.
• p2os_sound:
  • Interface: sound (see Section 6.24)
  • Configurations: none
  • Notes: Allows you to play pre-recorded sound files on an Amigobot (and other robots?).

Configuration file options

The configuration file options listed in Table 7.2 control how Player communicates with P2OS. Any option can be specified for any of the drivers listed in the previous section; if an option is specified for more than one driver, the value given last will be used.

Table: Configuration file options for the p2os_* drivers.

Name Type Default Meaning

port string "/dev/ttyS0" The serial port to be used

radio integer 0 Nonzero if a radio modem is being used; zero for a direct serial link

Notes

• The connection to the P2OS microcontroller is only kept open while at least one client has at least one of the P2OS-mediated devices open. When the last P2OS device is closed, the connection to P2OS is also closed. Implications include: odometry is reset to (0,0,0), motors might be turned off.
• Since the P2OS driver uses static C++ class members, only one P2OS robot can be controlled by Player at any given time. If you want to control more than one P2OS robots, you'll need to run a separate instance of Player for each.
• This driver can usually initiate a connection to P2OS even when P2OS was not properly shut down last time. However, if the connection to P2OS is interrupted (e.g., the serial cable is pulled out), then the driver is not likely to recover.
• This driver likely only works in Linux.