root / toolbox / serial.c @ 6ca98a3f
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| 1 | 6ca98a3f | Tom Mullins | #include <stdint.h> |
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| 2 | 20e5429c | Tom Mullins | #include <avr/io.h> |
| 3 | #include <avr/interrupt.h> |
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| 4 | 6ca98a3f | Tom Mullins | #include "serial.h" |
| 5 | 20e5429c | Tom Mullins | |
| 6 | static int rx_start = 0, rx_end = 0; |
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| 7 | 6ca98a3f | Tom Mullins | static uint8_t rx_buffer[RX_BUFFER_SIZE];
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| 8 | 20e5429c | Tom Mullins | |
| 9 | ISR(USART1_RX_vect) {
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| 10 | 6ca98a3f | Tom Mullins | uint8_t data = UDR1; |
| 11 | 20e5429c | Tom Mullins | int new_end = rx_end+1; |
| 12 | if (new_end == RX_BUFFER_SIZE) {
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| 13 | new_end = 0;
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| 14 | } |
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| 15 | if (new_end == rx_start) {
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| 16 | // TODO warn of buffer overflow?
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| 17 | } else {
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| 18 | rx_buffer[rx_end] = data; |
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| 19 | rx_end = new_end; |
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| 20 | } |
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| 21 | } |
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| 22 | |||
| 23 | void serial_init() {
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| 24 | 89915eeb | Tom Mullins | // baud = F_CPU / (div (UBRR + 1))
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| 25 | // where div = 16 if U2X = 0, or 8 otherwise
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| 26 | 20e5429c | Tom Mullins | uint16_t ubrr = F_CPU / 8 / BAUD_RATE - 1; |
| 27 | UBRR1H = ubrr >> 8;
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| 28 | UBRR1L = ubrr; |
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| 29 | // UMSEL = 0, asynchronous usart
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| 30 | // UPM = 0, parity check disabled
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| 31 | // USBS = 0, 1 stop bit
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| 32 | // UCSZ = 3, 8-bit
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| 33 | // U2X = 1, use 8 prescale instead of 16 for a more accurate baud rate
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| 34 | a7a56246 | Tom Mullins | UCSR1A = _BV(U2X1); |
| 35 | UCSR1B = _BV(RXCIE1) | _BV(RXEN1) | _BV(TXEN1); |
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| 36 | 20e5429c | Tom Mullins | UCSR1C = _BV(UCSZ11) | _BV(UCSZ10); |
| 37 | } |
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| 38 | |||
| 39 | int serial_read() {
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| 40 | int ret;
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| 41 | cli(); |
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| 42 | if (rx_start == rx_end) {
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| 43 | ret = -1;
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| 44 | } else {
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| 45 | ret = rx_buffer[rx_start]; |
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| 46 | rx_start++; |
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| 47 | 6ca98a3f | Tom Mullins | if (rx_start == RX_BUFFER_SIZE) {
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| 48 | 20e5429c | Tom Mullins | rx_start = 0;
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| 49 | 6ca98a3f | Tom Mullins | } |
| 50 | 20e5429c | Tom Mullins | } |
| 51 | sei(); |
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| 52 | return ret;
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| 53 | } |
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| 54 | |||
| 55 | 89915eeb | Tom Mullins | void serial_flush() {
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| 56 | cli(); |
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| 57 | rx_start = 0;
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| 58 | rx_end = 0;
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| 59 | sei(); |
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| 60 | } |
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| 61 | |||
| 62 | 6ca98a3f | Tom Mullins | uint8_t serial_read_blocking() {
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| 63 | 20e5429c | Tom Mullins | int c;
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| 64 | do {
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| 65 | c = serial_read(); |
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| 66 | } while (c < 0); |
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| 67 | return c;
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| 68 | } |
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| 69 | |||
| 70 | 6ca98a3f | Tom Mullins | void serial_write(uint8_t* data, int length) { |
| 71 | 20e5429c | Tom Mullins | int i;
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| 72 | for (i = 0; i < length; i++) { |
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| 73 | while (!(UCSR1A & _BV(UDRE1)));
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| 74 | UDR1 = data[i]; |
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| 75 | } |
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| 76 | } |