User Guide

50. else
51. set_motors(max_speed, max_speed-power_difference);
52. }
53. // A global ring buffer for data coming in. This is used by the
54. // read_next_byte() and previous_byte() functions, below.
55. char buffer[100];
56. // A pointer to where we are reading from.
57. unsigned char read_index = 0;
58. // Waits for the next byte and returns it. Runs play_check to keep
59. // the music playing and serial_check to keep receiving bytes.
60. // Calls pid_check() to keep following the line.
61. char read_next_byte()
62. {
63. while(serial_get_received_bytes() == read_index)
64. {
65. serial_check();
66. play_check();
67. // pid_check takes some time; only run it if we don’t have more bytes to process
68. if(serial_get_received_bytes() == read_index)
69. pid_check();
70. }
71. char ret = buffer[read_index];
72. read_index ++;
73. if(read_index >= 100)
74. read_index = 0;
75. return ret;
76. }
77. // Backs up by one byte in the ring buffer.
78. void previous_byte()
79. {
80. read_index --;
81. if(read_index == 255)
82. read_index = 99;
83.
}
84. // Returns true if and only if the byte is a command byte (>= 0x80).
85. char is_command(char byte)
86. {
87. if (byte < 0)
88. return 1;
89. return 0;
90. }
91. // Returns true if and only if the byte is a data byte (< 0x80).
92. char is_data(char byte)
93. {
94. if (byte < 0)
95. return 0;
96. return 1;
97. }
98. // If it’s not a data byte, beeps, backs up one, and returns true.
99. char check_data_byte(char byte)
100. {
101. if(is_data(byte))
102. return 0;
103. play(“o3c”);
104. clear();
105. print(“Bad data”);
106. lcd_goto_xy(0,1);
107. print_hex_byte(byte);
108. previous_byte();
109. return 1;
110. }
1. /////////////////////////////////////////////////////////////////////
2. // COMMAND FUNCTIONS
3. //
4. // Each function in this section corresponds to a single serial
5. // command. The functions are expected to do their own argument
6.
// handling using read_next_byte() and check_data_byte().
7. // Sends the version of the slave code that is running.
8. // This function also shuts down the motors and disables PID, so it is
9. // useful as an initial command.
10. void send_signature()
11. {
12. serial_send_blocking(“3pi1.0”, 6);
13. set_motors(0,0);
14. pid_enabled = 0;
15. }
16. // Reads the line sensors and sends their values. This function can
17. // do either calibrated or uncalibrated readings. When doing calibrated readings,
18. // it only performs a new reading if we are not in PID mode. Otherwise, it sends