Stijn Sontrop
Function to get the ID of iButtons via the 1-wire bus
main.cpp@0:39cce56e485b, 2011-02-12 (annotated)
- Committer:
- StijnS
- Date:
- Sat Feb 12 11:00:05 2011 +0000
- Revision:
- 0:39cce56e485b
Who changed what in which revision?
| User | Revision | Line number | New contents of line |
|---|---|---|---|
| StijnS | 0:39cce56e485b | 1 | #include "mbed.h" |
| StijnS | 0:39cce56e485b | 2 | #define ibuttonpin p20 |
| StijnS | 0:39cce56e485b | 3 | |
| StijnS | 0:39cce56e485b | 4 | Serial pc(USBTX, USBRX); |
| StijnS | 0:39cce56e485b | 5 | |
| StijnS | 0:39cce56e485b | 6 | DigitalInOut ibuttondata(ibuttonpin); |
| StijnS | 0:39cce56e485b | 7 | |
| StijnS | 0:39cce56e485b | 8 | typedef struct { |
| StijnS | 0:39cce56e485b | 9 | unsigned char family; |
| StijnS | 0:39cce56e485b | 10 | unsigned char serial[6]; |
| StijnS | 0:39cce56e485b | 11 | unsigned char crc; |
| StijnS | 0:39cce56e485b | 12 | unsigned char valid; |
| StijnS | 0:39cce56e485b | 13 | } ibuttonvalue; |
| StijnS | 0:39cce56e485b | 14 | |
| StijnS | 0:39cce56e485b | 15 | |
| StijnS | 0:39cce56e485b | 16 | unsigned char crc8(unsigned char crc, unsigned char data) { //Calculate CRC8 |
| StijnS | 0:39cce56e485b | 17 | crc = crc ^ data; |
| StijnS | 0:39cce56e485b | 18 | for (int i = 0; i < 8; i++) { |
| StijnS | 0:39cce56e485b | 19 | if (crc & 0x01) { |
| StijnS | 0:39cce56e485b | 20 | crc = (crc >> 1) ^ 0x8C; |
| StijnS | 0:39cce56e485b | 21 | } else { |
| StijnS | 0:39cce56e485b | 22 | crc >>= 1; |
| StijnS | 0:39cce56e485b | 23 | } |
| StijnS | 0:39cce56e485b | 24 | } |
| StijnS | 0:39cce56e485b | 25 | return crc; |
| StijnS | 0:39cce56e485b | 26 | } |
| StijnS | 0:39cce56e485b | 27 | |
| StijnS | 0:39cce56e485b | 28 | void OneWireReset(void) { //Generates reset on 1-wire bus |
| StijnS | 0:39cce56e485b | 29 | ibuttondata.output(); |
| StijnS | 0:39cce56e485b | 30 | ibuttondata = 0; |
| StijnS | 0:39cce56e485b | 31 | wait_us(500); |
| StijnS | 0:39cce56e485b | 32 | ibuttondata.input(); |
| StijnS | 0:39cce56e485b | 33 | wait_us(500); |
| StijnS | 0:39cce56e485b | 34 | } |
| StijnS | 0:39cce56e485b | 35 | |
| StijnS | 0:39cce56e485b | 36 | void OneWireOutByte(unsigned char data) { //Write byte on 1-wire bus |
| StijnS | 0:39cce56e485b | 37 | for (int n = 8;n!=0; n--) { |
| StijnS | 0:39cce56e485b | 38 | if ((data & 0x01) == 1) { |
| StijnS | 0:39cce56e485b | 39 | ibuttondata.output(); |
| StijnS | 0:39cce56e485b | 40 | ibuttondata = 0; |
| StijnS | 0:39cce56e485b | 41 | wait_us(5); |
| StijnS | 0:39cce56e485b | 42 | ibuttondata.input(); |
| StijnS | 0:39cce56e485b | 43 | wait_us(60); |
| StijnS | 0:39cce56e485b | 44 | } else { |
| StijnS | 0:39cce56e485b | 45 | ibuttondata.output(); |
| StijnS | 0:39cce56e485b | 46 | wait_us(60); |
| StijnS | 0:39cce56e485b | 47 | ibuttondata.input(); |
| StijnS | 0:39cce56e485b | 48 | } |
| StijnS | 0:39cce56e485b | 49 | data = data >> 1; |
| StijnS | 0:39cce56e485b | 50 | } |
| StijnS | 0:39cce56e485b | 51 | } |
| StijnS | 0:39cce56e485b | 52 | |
| StijnS | 0:39cce56e485b | 53 | unsigned char OneWireReadByte(void) { //Read 1 byte from 1-wire bus |
| StijnS | 0:39cce56e485b | 54 | unsigned char d = 0; |
| StijnS | 0:39cce56e485b | 55 | unsigned char b; |
| StijnS | 0:39cce56e485b | 56 | for (int n = 0; n<8; n++) { |
| StijnS | 0:39cce56e485b | 57 | ibuttondata.output(); |
| StijnS | 0:39cce56e485b | 58 | ibuttondata = 0; |
| StijnS | 0:39cce56e485b | 59 | wait_us(5); |
| StijnS | 0:39cce56e485b | 60 | ibuttondata.input(); |
| StijnS | 0:39cce56e485b | 61 | wait_us(5); |
| StijnS | 0:39cce56e485b | 62 | b = ibuttondata; |
| StijnS | 0:39cce56e485b | 63 | wait_us(50); |
| StijnS | 0:39cce56e485b | 64 | d = (d >> 1) | (b << 7); |
| StijnS | 0:39cce56e485b | 65 | } |
| StijnS | 0:39cce56e485b | 66 | return d; |
| StijnS | 0:39cce56e485b | 67 | } |
| StijnS | 0:39cce56e485b | 68 | |
| StijnS | 0:39cce56e485b | 69 | ibuttonvalue DetectiButton(void) { //Function to detect an iButton en give back its contents |
| StijnS | 0:39cce56e485b | 70 | ibuttonvalue detect; |
| StijnS | 0:39cce56e485b | 71 | unsigned char crc = 0; |
| StijnS | 0:39cce56e485b | 72 | OneWireReset(); |
| StijnS | 0:39cce56e485b | 73 | OneWireOutByte(0x33); //Read Rom cmd |
| StijnS | 0:39cce56e485b | 74 | detect.family = OneWireReadByte(); |
| StijnS | 0:39cce56e485b | 75 | crc = crc8(crc, detect.family); |
| StijnS | 0:39cce56e485b | 76 | if (detect.family == 0x00 || detect.family == 0xFF) { |
| StijnS | 0:39cce56e485b | 77 | detect.valid = 0; |
| StijnS | 0:39cce56e485b | 78 | return detect; //No iButton detected |
| StijnS | 0:39cce56e485b | 79 | } |
| StijnS | 0:39cce56e485b | 80 | for (int i = 0; i <6; i++) { |
| StijnS | 0:39cce56e485b | 81 | detect.serial[i] = OneWireReadByte(); |
| StijnS | 0:39cce56e485b | 82 | crc = crc8(crc, detect.serial[i]); |
| StijnS | 0:39cce56e485b | 83 | } |
| StijnS | 0:39cce56e485b | 84 | detect.crc = OneWireReadByte(); |
| StijnS | 0:39cce56e485b | 85 | if (crc == detect.crc) { //If CRC is valid: set valid flag to 1 |
| StijnS | 0:39cce56e485b | 86 | detect.valid = 1; |
| StijnS | 0:39cce56e485b | 87 | } |
| StijnS | 0:39cce56e485b | 88 | return detect; |
| StijnS | 0:39cce56e485b | 89 | } |
| StijnS | 0:39cce56e485b | 90 | int main() { |
| StijnS | 0:39cce56e485b | 91 | ibuttonvalue detected; |
| StijnS | 0:39cce56e485b | 92 | while(1) { |
| StijnS | 0:39cce56e485b | 93 | detected = DetectiButton(); |
| StijnS | 0:39cce56e485b | 94 | if (detected.valid == 1) { //Test valid flag |
| StijnS | 0:39cce56e485b | 95 | pc.printf("iButton Family: %X Serial: ", detected.family); |
| StijnS | 0:39cce56e485b | 96 | for (int i = 0; i < 6; i++) { |
| StijnS | 0:39cce56e485b | 97 | pc.printf("%X", detected.serial[i]); |
| StijnS | 0:39cce56e485b | 98 | } |
| StijnS | 0:39cce56e485b | 99 | pc.printf(" CRC: %X\n", detected.crc); |
| StijnS | 0:39cce56e485b | 100 | } |
| StijnS | 0:39cce56e485b | 101 | } |
| StijnS | 0:39cce56e485b | 102 | } |