Sensors API for Robolocust iRobot Create Command Module control program. More...
Go to the source code of this file.
Functions | |
| void | lo_init_sensors (void) |
| void | lo_toggle_rear_bumps_spin (void) |
| void | lo_sensors (void) |
| char | lo_get_sensor (unsigned char index) |
| void | lo_update_odometry (int distance, int angle) |
| void | lo_update_pending_odometry (int distance, int angle) |
| char | lo_sensors_pending (void) |
| Check if sensor data is available for sending to the high level. | |
| char | lo_rear_bumps_spin (void) |
| void | lo_send_sensors (void) |
| Send pending/current sensor data to the high level. | |
| void | lo_enable_rear_bumps (int) |
| void | lo_disable_rear_bumps (int) |
| void | lo_toggle_rear_bumps (void) |
Sensors API for Robolocust iRobot Create Command Module control program.
This file defines an API for retrieving relevant sensor data from the iRobot Create using the Open Interface.
Definition in file LoSensors.h.
| void lo_enable_rear_bumps | ( | int | ) |
On its rear, the robot sports a pair of Sharp GP2D15 IR proximity detectors to help prevent bumping into things as it backs up. Since the Command Module is also accessed from the rear, these two sensors detect the user's hand as soon as the robot is turned on and cause it to spin and move forward, away from the "obstacle" behind it.
This can be very annoying, especially when we want the robot to remain stationary at some fixed initial starting position prior to the commencement of an experiment/run.
To work around this behaviour, we allow the high-level controller to specify when the rear bumpers should be enabled and when they should be ignored. Furthermore, the user can also toggle these sensors by using the SPOT button on the Roomba Remote.
These functions turn the rear bumpers on/off.
Definition at line 164 of file LoSensors.c.
References lo_lobyte().
| char lo_get_sensor | ( | unsigned char | index | ) |
The lo_sensors() function retrieves the current sensor data from the Create robot and stores it in an internal array. This function returns a sensor byte given its index.
NOTE: The indices into the internal sensor data array are defined in LoCMInterface.h.
Definition at line 282 of file LoSensors.c.
Referenced by lo_bumps(), lo_cliffs(), lo_remote(), and lo_wheel_drops().
| void lo_init_sensors | ( | void | ) |
This function initializes the sensors module. It must be called early during the low-level controller's initialization sequence. This function is responsible for properly debouncing the rear proximity detectors.
Definition at line 158 of file LoSensors.c.
References lo_add_timer1_cb().
| char lo_rear_bumps_spin | ( | void | ) |
When the rear bump sensors are active, the low-level controller can be configured to respond by simply stopping the robot (default behaviour) or by spinning in-place and then moving up. This function returns false if the former configuration is in effect and true for the latter.
Definition at line 325 of file LoSensors.c.
Referenced by lo_bumps().
| void lo_send_sensors | ( | void | ) |
Send pending/current sensor data to the high level.
Definition at line 333 of file LoSensors.c.
References lo_tx(), LOBOT_ACK_SENSORS, and LOBOT_SENSORS_SIZE.
| void lo_sensors | ( | void | ) |
This function retrieves the current sensor data from the Create robot. The Create is queried for all its sensor packets.
To indicate to the main program that new sensor data has been retrieved, it sets a flag.
The main loop of the low-level Command Module control program will test this flag in each iteration and then send the sensor data off to the high level.
Definition at line 228 of file LoSensors.c.
References lo_io_error(), lo_rx(), lo_tx(), lo_update_odometry(), LOBOT_OI_CMD_SENSORS, LOBOT_OI_SENSOR_GROUP_6, LOBOT_SENSORS_BUMPS, and LOBOT_SENSORS_SPIN_FLAG.
| char lo_sensors_pending | ( | void | ) |
Check if sensor data is available for sending to the high level.
Definition at line 319 of file LoSensors.c.
| void lo_toggle_rear_bumps_spin | ( | void | ) |
When the rear bumpers are enabled, the low-level controller will respond to rear bump events in one of two ways:
1. just stop the robot when either of the rear bump sensors is active
2. stop the robot, then spin it a small amount either clockwise or counterclockwise depending on which side the obstacle appears and, finally, move the robot forward a little bit
By default, the low-level controller simply stops the robot. However, the high-level controller can instruct the low-level controller to adopt the second action described above by passing a '1' as the parameter to the LOBOT_CMD_ENABLE_REAR_BUMPS command.
Additionally, the user can switch between the above two actions by using the MAX button on the Roomba Remote.
This function toggles the flag responsible for deciding which of the above two actions to take when a rear bump event is detected.
Definition at line 183 of file LoSensors.c.
| void lo_update_odometry | ( | int | distance, | |
| int | angle | |||
| ) |
In response to events such as bumps and cliffs, the low-level controller backs up the robot (or moves it forward if that is the appropriate response) and spins it in place by some small amount. When we do that, we should add the amount of linear and rotational displacement to the encoder's estimates. Otherwise, the next sensor packet we send to the high-level controller will report odometry values associated with the sensor query sent to the iRobot Create prior to the low-level controller's bumps/cliffs avoidance. These incorrect odometry estimates can wreak havoc on any high-level localization modules and other parts that rely on reasonably accurate odometry from the low-level.
This function adds the given displacements to the low-level sensor packet that is currently pending, i.e., "waiting" to be sent to the high-level controller.
Definition at line 291 of file LoSensors.c.
References lo_hibyte(), lo_lobyte(), lo_make_word(), LOBOT_SENSORS_ANGLE_HI, and LOBOT_SENSORS_DISTANCE_HI.
Referenced by lo_bumps(), lo_cliffs(), and lo_sensors().
| void lo_update_pending_odometry | ( | int | distance, | |
| int | angle | |||
| ) |
When the high-level controller sends a SPIN command, it will specify the amount to be spun. However, the actual amount spun may be slightly more or less (due to motor/encoder errors). Furthermore, the robot may also experience some slight translational motion in addition to the requested rotation.
To ensure that the high-level receives accurate motion updates in the next SENSORS acknowledgement, we should record the translation and rotation resulting from the SPIN command in some temporary variables and add those values to the encoder data retrieved from the Create when the time comes to send the next ACK_SENSORS.
This function updates the temporary variables alluded to above.
Definition at line 308 of file LoSensors.c.
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