Kevin Anderson / Mbed 2 deprecated DataCommFreedom

Using FRDM Board to output data and a clock for communications example.

Dependencies:   mbed

main.cpp@4:39a777388acd, 2015-03-23 (annotated)

Committer:
askksa12543
Date:
Mon Mar 23 13:54:41 2015 +0000
Revision:
4:39a777388acd
Parent:
3:027d30718bbc
Child:
5:8c012e2c1ba8
updated

Who changed what in which revision?

UserRevisionLine numberNew contents of line
askksa12543 2:11f32d8cfa11 1 //project to include preamble, addressing, control, error control.
askksa12543 2:11f32d8cfa11 2 //currently fixed size data field but doesn't have to be. (post amble if not fixed size)
askksa12543 2:11f32d8cfa11 3
askksa12543 0:7c7f4b30d64f 4 #include "mbed.h"
askksa12543 0:7c7f4b30d64f 5 #include "stdio.h"
askksa12543 0:7c7f4b30d64f 6
askksa12543 2:11f32d8cfa11 7 #define MAX 100 //set the size of the character data storage array
askksa12543 3:027d30718bbc 8 #define PREAMBLE 0x7E //preamble of 01111110
askksa12543 2:11f32d8cfa11 9
askksa12543 2:11f32d8cfa11 10 DigitalOut myled(LED1); // red led on board
askksa12543 2:11f32d8cfa11 11 DigitalOut clock_pin(D8), serial_out(D7); //send clock pulse and tx
askksa12543 0:7c7f4b30d64f 12 Timer t; //timer for controlling the clock and data skew
askksa12543 2:11f32d8cfa11 13 int msecs, sksecs; //clock time needed for data transfer and skew time
askksa12543 0:7c7f4b30d64f 14 int skew_flag; //skew flag for while loop
askksa12543 3:027d30718bbc 15 unsigned char pre = PREAMBLE;
askksa12543 3:027d30718bbc 16 unsigned char data[100] = "Hi!"; //data output
askksa12543 3:027d30718bbc 17 int done = 0, i = 0, j = 128; //increment variables
askksa12543 0:7c7f4b30d64f 18
askksa12543 0:7c7f4b30d64f 19 int main() {
askksa12543 0:7c7f4b30d64f 20
askksa12543 0:7c7f4b30d64f 21 //turn on red led to show programming has worked
askksa12543 0:7c7f4b30d64f 22 myled = 0;
askksa12543 0:7c7f4b30d64f 23 //initialize output pins
askksa12543 0:7c7f4b30d64f 24 clock_pin = 0;
askksa12543 0:7c7f4b30d64f 25 serial_out = 0;
askksa12543 0:7c7f4b30d64f 26 //skew flag
askksa12543 0:7c7f4b30d64f 27 skew_flag = 1;
askksa12543 0:7c7f4b30d64f 28 //set timers
askksa12543 1:4c0c28cc2b2c 29 msecs = 2000;
askksa12543 1:4c0c28cc2b2c 30 sksecs = 1800;
askksa12543 0:7c7f4b30d64f 31
askksa12543 3:027d30718bbc 32 //output preamble
askksa12543 3:027d30718bbc 33 while(!done)
askksa12543 3:027d30718bbc 34 {
askksa12543 3:027d30718bbc 35 //start timer for clock
askksa12543 3:027d30718bbc 36 t.start();
askksa12543 3:027d30718bbc 37 //wait until the timer has reached the set time.
askksa12543 3:027d30718bbc 38 while(t.read_ms() < msecs)
askksa12543 3:027d30718bbc 39 {
askksa12543 3:027d30718bbc 40 //extract data just before clock goes high
askksa12543 3:027d30718bbc 41 if(!clock_pin && skew_flag && t.read_ms() > sksecs)
askksa12543 3:027d30718bbc 42 {
askksa12543 3:027d30718bbc 43 //extract data bit
askksa12543 3:027d30718bbc 44 serial_out = (pre / j) % 2;
askksa12543 3:027d30718bbc 45 skew_flag = 0;
askksa12543 3:027d30718bbc 46 j /= 2; //decrement j to get to next bit location
askksa12543 3:027d30718bbc 47 }
askksa12543 3:027d30718bbc 48 }
askksa12543 3:027d30718bbc 49 //stop and reset the timer
askksa12543 3:027d30718bbc 50 t.stop();
askksa12543 3:027d30718bbc 51 t.reset();
askksa12543 3:027d30718bbc 52 //switch clock signal
askksa12543 3:027d30718bbc 53 clock_pin = !clock_pin;
askksa12543 3:027d30718bbc 54 //reset skew flag
askksa12543 3:027d30718bbc 55 skew_flag = 1;
askksa12543 3:027d30718bbc 56 //last preamble bit sent - reset/increment variables
askksa12543 3:027d30718bbc 57 if(j==0)
askksa12543 3:027d30718bbc 58 {
askksa12543 3:027d30718bbc 59 done = 1;
askksa12543 3:027d30718bbc 60 j = 128;
askksa12543 3:027d30718bbc 61 }
askksa12543 3:027d30718bbc 62 }
askksa12543 3:027d30718bbc 63
askksa12543 3:027d30718bbc 64 //reset done
askksa12543 3:027d30718bbc 65 done = 0;
askksa12543 3:027d30718bbc 66
askksa12543 0:7c7f4b30d64f 67 //output a clock pulse and data.
askksa12543 3:027d30718bbc 68 while(!done)
askksa12543 0:7c7f4b30d64f 69 {
askksa12543 0:7c7f4b30d64f 70 //start timer for clock
askksa12543 0:7c7f4b30d64f 71 t.start();
askksa12543 0:7c7f4b30d64f 72 //wait until the timer has reached the set time.
askksa12543 0:7c7f4b30d64f 73 while(t.read_ms() < msecs)
askksa12543 0:7c7f4b30d64f 74 {
askksa12543 2:11f32d8cfa11 75 //extract data just before clock goes high
askksa12543 0:7c7f4b30d64f 76 if(!clock_pin && skew_flag && t.read_ms() > sksecs)
askksa12543 0:7c7f4b30d64f 77 {
askksa12543 2:11f32d8cfa11 78 //extract data bit
askksa12543 2:11f32d8cfa11 79 serial_out = (data[i] / j) % 2;
askksa12543 0:7c7f4b30d64f 80 skew_flag = 0;
askksa12543 2:11f32d8cfa11 81 j /= 2; //decrement j to get to next bit location
askksa12543 0:7c7f4b30d64f 82 }
askksa12543 0:7c7f4b30d64f 83 }
askksa12543 0:7c7f4b30d64f 84 //stop and reset the timer
askksa12543 0:7c7f4b30d64f 85 t.stop();
askksa12543 0:7c7f4b30d64f 86 t.reset();
askksa12543 0:7c7f4b30d64f 87 //switch clock signal
askksa12543 0:7c7f4b30d64f 88 clock_pin = !clock_pin;
askksa12543 0:7c7f4b30d64f 89 //reset skew flag
askksa12543 0:7c7f4b30d64f 90 skew_flag = 1;
askksa12543 2:11f32d8cfa11 91 //last bit sent - reset/increment variables
askksa12543 2:11f32d8cfa11 92 if(j==0)
askksa12543 2:11f32d8cfa11 93 {
askksa12543 2:11f32d8cfa11 94 j=128;
askksa12543 2:11f32d8cfa11 95 i++;
askksa12543 2:11f32d8cfa11 96 }
askksa12543 3:027d30718bbc 97 //finished sending data
askksa12543 3:027d30718bbc 98 if(i>2)
askksa12543 3:027d30718bbc 99 {
askksa12543 3:027d30718bbc 100 done = 1;
askksa12543 3:027d30718bbc 101 }
askksa12543 0:7c7f4b30d64f 102 }
askksa12543 3:027d30718bbc 103 //turn off red led to show sending has finished
askksa12543 3:027d30718bbc 104 myled = 1;
askksa12543 1:4c0c28cc2b2c 105 }
askksa12543 1:4c0c28cc2b2c 106
askksa12543 4:39a777388acd 107 //crc = x^4+x+1
askksa12543 4:39a777388acd 108 //put char data into unsigned short temp variable, then shift << 5. % this number by the decimal equivalent of binary representation of
askksa12543 4:39a777388acd 109 //the crc code and save and send it as a separate 5 bits. On the receive side save each byte in the temp character and then the next five
askksa12543 4:39a777388acd 110 //bytes in a temp variable - after receiving 13 bits stick data in unsigned short variable << 5 add the recieved 5 bits and then % by
askksa12543 4:39a777388acd 111 // the crc decimal equivalent, if that equals 0, save the temp character in the permanent character array and receive the next bits.