Axis Communications Dynamixel AX-12 - Manual (Page 32)

DYNAMIXEL AX-12
When changing the direction, the TXD_SHIFT_REGISTER_EMPTY_BIT must be
checked.
The following is an example program that sends an Instruction Packet.
LINE 1 DIRECTION_PORT = TX_DIRECTION;
LINE 2 TxDByte(0xff);
LINE 3 TxDByte(0xff);
LINE 4 TxDByte(bID);
LINE 5 TxDByte(bLength);
LINE 6 TxDByte(bInstruction);
LINE 7 TxDByte(Parameter0); TxDByte(Parameter1); …
LINE 8 DisableInterrupt(); // interrupt should be disable
LINE 9 TxDByte(Checksum); //last TxD
LINE 10 while(!TXD_SHIFT_REGISTER_EMPTY_BIT); //Wait till last data bit has been sent
LINE 11 DIRECTION_PORT = RX_DIRECTION; //Direction change to RXD
LINE 12 EnableInterrupt(); // enable interrupt again
Please note the important lines between LINE 8 and LINE 12. Line 8 is necessary since
an interrupt here may cause a delay longer than the return delay time and corruption to
the front of the status packet may occur.
Byte to Byte Time The delay time between bytes when sending an instruction packet. If the delay time is
over 100ms, then the Dynamixel actuator recognizes this as a communication problem
and waits for the next header (0xff 0xff) of a packet again.
0xFF 0xFF ID Length
Byte To Byte Time
The following is the source code of a program (Example.c) that accesses the Dynamixel
actuator using the Atmega 128.
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