Sending, Receiving and Processing Messages NQC Tutorial pp.34-36

Sending and Receiving Messages A robot can use the command SendMessage() to send a value (0-255) over the infra-red port. All other robots receive this message and store it. The program in a robot can ask for the value of the last message received using Message(). Based on this value the program can make the robot perform certain actions.

Master and Slave Two cooperating robots can interact: Master-- sends a message Slave-- responds to the message In the following example we will develop a communication protocol in which we define three messages: 1: go forward, 2: go backward, and 3: stop.

task main() // SLAVE { while (true) { ClearMessage(); until (Message() != 0); if (Message() == 1) {OnFwd(OUT_A+OUT_C);} if (Message() == 2) {OnRev(OUT_A+OUT_C);} if (Message() == 3) {Off(OUT_A+OUT_C);} } task main() // MASTER { SendMessage(1); Wait(200); SendMessage(2); Wait(200); SendMessage(3); }

Messaging Protocol for Nursebot start The message will represent the destination for nursebot. 6

When your nursebot is started, it should remain stationary at the starting point until it receives a message detailing the destination. At that time it should acknowledge receipt of the message by tone sounding. That is, if the destination is 4, sound a tone 4 times. (Hints: use a repeat loop and don’t forget to add a delay.)