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1	c4f160ba	Tom Mullins	#include <avr/io.h>
2			#include <avr/interrupt.h>
3	0167b233	Aaron Perley	#include <util/delay.h>
4	08af0896	Tom Mullins	#include "tiny-twi.h"
5	c4f160ba	Tom Mullins
6	797244ed	Aaron Perley	#define SDA PB0
7			#define SCL PB2
8
9	cbe25c0a	tmullins	#define RECV_BUF_SIZE 3
10	b3a1dae4	Tom Mullins	#define SEND_BUF_SIZE 100
11	c4f160ba	Tom Mullins
12			uint8_t address;
13
14	08af0896	Tom Mullins	typedef enum {
15	c4f160ba	Tom Mullins	IDLE,
16			ADDRESS,
17			SEND_READ_ACK,
18			SEND_WRITE_ACK,
19			SEND_DATA,
20			RECV_DATA,
21			RECV_ACK
22	08af0896	Tom Mullins	} state_t;
23	c4f160ba	Tom Mullins
24	08af0896	Tom Mullins	state_t state;
25	c4f160ba	Tom Mullins	uint8_t recv_idx;
26			uint8_t recv_data[RECV_BUF_SIZE];
27	0167b233	Aaron Perley	slave_rx_t onDataRecieved;
28	b3a1dae4	Tom Mullins	struct {
29			uint8_t start;
30			uint8_t end;
31			uint8_t data[SEND_BUF_SIZE];
32			bool full;
33			} send_queue;
34	c4f160ba	Tom Mullins
35			static void twi_set_ctr(char n) {
36	797244ed	Aaron Perley	USISR = n;
37	16da2c8f	Tom Mullins	}
38
39	c4f160ba	Tom Mullins	static void twi_ready() {
40	797244ed	Aaron Perley	USISR = _BV(USISIF) \| _BV(USIOIF) \| _BV(USIPF) \| _BV(USIDC);
41			DDRB \|= _BV(SCL); //SCL output
42			DDRB &= ~_BV(SDA); //SDA input
43	c4f160ba	Tom Mullins
44			// enable start condition interrupt
45			USICR \|= _BV(USISIE);
46
47			// disable counter overflow interrupt
48			USICR &= ~_BV(USIOIE);
49
50			state = IDLE;
51			}
52
53			static void twi_start() {
54	797244ed	Aaron Perley	// enable counter overflow interrupt (fires after 8 bits)
55			USICR \|= _BV(USIOIE);
56
57			USISR = _BV(USISIF);
58	c4f160ba	Tom Mullins
59			// zero counter
60			twi_set_ctr(0);
61
62			state = ADDRESS;
63			recv_idx = 0;
64			}
65
66			static void twi_send_ack(char is_read) {
67
68			// set counter to 14
69			twi_set_ctr(14);
70
71			// set SDA low
72			USIDR = 0;
73	797244ed	Aaron Perley	DDRB \|= _BV(SDA);
74	c4f160ba	Tom Mullins
75			// set state
76			state = is_read? SEND_READ_ACK : SEND_WRITE_ACK;
77			}
78
79	240c122b	Tom Mullins	static void twi_send_data() {
80			twi_set_ctr(0);
81	b3a1dae4	Tom Mullins	if (send_queue.start == send_queue.end && !send_queue.full) {
82			USIDR = 0;
83			} else {
84			USIDR = send_queue.data[send_queue.start++];
85			if (send_queue.start == SEND_BUF_SIZE)
86			send_queue.start = 0;
87			send_queue.full = 0;
88			}
89	240c122b	Tom Mullins	DDRB \|= _BV(SDA);
90			state = SEND_DATA;
91			}
92
93			static void twi_recv_ack() {
94			twi_set_ctr(14);
95			DDRB &= ~_BV(SDA);
96			state = RECV_ACK;
97			}
98
99	c4f160ba	Tom Mullins	ISR(USI_START_vect) {
100			twi_start();
101			}
102
103			ISR(USI_OVF_vect) {
104	6185434e	Tom Mullins	uint8_t input = USIDR; // TODO make sure this is correct
105	c4f160ba	Tom Mullins	switch (state) {
106
107			case IDLE:
108			// shouldn't reach here
109			twi_ready();
110			break;
111
112			case ADDRESS:
113			if (input >> 1 == address) {
114			// send ack
115			twi_send_ack(input & 1);
116			} else {
117			// go back to listening for start condition
118			twi_ready();
119			}
120			break;
121
122			case SEND_WRITE_ACK:
123	6185434e	Tom Mullins	if (recv_idx == RECV_BUF_SIZE) {
124			twi_ready();
125			onDataRecieved(recv_data, RECV_BUF_SIZE);
126			} else {
127			DDRB &= ~_BV(SDA);
128			state = RECV_DATA;
129			}
130	c4f160ba	Tom Mullins	break;
131
132			case RECV_DATA:
133			twi_send_ack(0);
134	6185434e	Tom Mullins	recv_data[recv_idx] = input;
135	c4f160ba	Tom Mullins	recv_idx++;
136			break;
137
138			case SEND_READ_ACK:
139	240c122b	Tom Mullins	twi_send_data();
140	c4f160ba	Tom Mullins	break;
141
142			case SEND_DATA:
143	240c122b	Tom Mullins	twi_recv_ack();
144	c4f160ba	Tom Mullins	break;
145
146			case RECV_ACK:
147	240c122b	Tom Mullins	if (input & 1) {
148			// received nak
149			twi_ready();
150			} else {
151			// received ack
152			twi_send_data();
153			}
154	c4f160ba	Tom Mullins	break;
155			}
156	797244ed	Aaron Perley	USISR = _BV(USIOIF) \| (USISR & 0xF);
157	c4f160ba	Tom Mullins	}
158
159	0167b233	Aaron Perley	void smb_init(slave_rx_t callback) {
160	c4f160ba	Tom Mullins	// TODO do we want USICS0 (3)?
161			USICR = _BV(USIWM1) \| _BV(USIWM0) \| _BV(USICS1);
162	797244ed	Aaron Perley	PORTB \|= _BV(SDA) \| _BV(SCL);
163	c4f160ba	Tom Mullins	twi_ready();
164	0167b233	Aaron Perley	onDataRecieved = callback;
165	c4f160ba	Tom Mullins	}
166
167			void smb_set_address(uint8_t addr) {
168			address = addr;
169			}
170	0167b233	Aaron Perley
171	cbe25c0a	tmullins	void smb_send_data(uint8_t* data, uint8_t length) {
172	b3a1dae4	Tom Mullins	uint8_t i;
173			for (i=0; i<length && !send_queue.full; i++) {
174			send_queue.data[send_queue.end++] = data[i];
175			if (send_queue.end == SEND_BUF_SIZE)
176			send_queue.end = 0;
177			if (send_queue.end == send_queue.start)
178			send_queue.full = 1;
179			}
180			}

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root / scout_avr / bom / tiny-twi.c @ cbe25c0a