Remote Control - NEX ROBOTICS Fire Bird V ATMEGA2560 HEXAPOD User Manual

Fire Bird V ATMEGA2560 Hexapod Robot User Guide
6.7 Robot clockwise (CW) and counter clockwise(CCW) rotation
"clock_wise_step()" and "counter_clock_wise_step()" rotates the robot in the desired
direction. Again in this case motion is planned in conservative way. In the CW & CCW legs are
lifted and moved in the desired direction call function "clock_wise_step ()" for CW & "anti_
clock_wise_step ()" for CCW step. Once all the legs are moved, robot pushes itself in the
desired direction by calling the function "robot_stand_position ()" Turning can be done faster
as shown in the "Hexapod 2" video in the documentation CD.

6.8 Remote control

Functions described in this section are used in Hexapod_remote_control code.
In this application robot acts as master and remote act as slave. When robot wants data related to
joystick position, it sends string of 4 characters as "NEXR", at 115200 bps to the remote via
XBee wireless module. In return to this string remote sends header byte string as "FB" followed
by 8 data bytes containing information of the joystick, Remote control's tilt, pan angel and digital
switch position.
Transmitting packet from the robot:
N - 1st byte of packet
E - 2nd byte of packet
X - 3rd byte of packet
R - 4th byte of packet
Receiving packet to robot from remote:
F - 1st byte of packet (1st header byte)
B - 2nd byte of packet (2nd header byte)
Byte1 - 3rd byte of packet (Vertical position of left joystick)
Byte2 - 4th byte of packet (horizontal position of left joystick)
Byte3 - 5th byte of packet (Vertical position of right joystick)
Byte4 - 6th byte of packet (horizontal position of right joystick)
Byte5 - 7th byte of packet (Accelerometer x axis position)
Byte6 - 8th byte of packet (Accelerometer y axis position)
Byte7 - 9th byte of packet (Battery Voltage)
Byte8 - 10th byte of packet (out of 8 bit data bit0 shows right switch and bit1 shows left
switch position and other bit are left for other user application)
The right joystick is used for robot motion control and left joystick is used for servo mounted
camera pod control. Remote control also has built-in 2 axis accelerometer and switches which
can be used for adding more functionality.
Communication is synchronized in the timer 1 ISR. In the demo code robot asks for the data
form the remote control once every 200ms. Data update rate can be increased up to 10 ms by
changing comparison value from 80 to 4 in the, if statement "if (serial_communication_interval
> 80)".
The remote replies the current joysticks, accelerometer, and switch position data in the packet
form. The data packet is received in the UART0 ISR function "SIGNAL
© NEX Robotics Pvt. Ltd. and ERTS Lab IIT Bombay, INDIA 28