root / branches / autonomous_recharging / code / projects / libbayboard / i2c.c @ 968
History | View | Annotate | Download (11 KB)
1 | 968 | ttf | /**
|
---|---|---|---|
2 | * Copyright (c) 2007 Colony Project
|
||
3 | *
|
||
4 | * Permission is hereby granted, free of charge, to any person
|
||
5 | * obtaining a copy of this software and associated documentation
|
||
6 | * files (the "Software"), to deal in the Software without
|
||
7 | * restriction, including without limitation the rights to use,
|
||
8 | * copy, modify, merge, publish, distribute, sublicense, and/or sell
|
||
9 | * copies of the Software, and to permit persons to whom the
|
||
10 | * Software is furnished to do so, subject to the following
|
||
11 | * conditions:
|
||
12 | *
|
||
13 | * The above copyright notice and this permission notice shall be
|
||
14 | * included in all copies or substantial portions of the Software.
|
||
15 | *
|
||
16 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
|
||
17 | * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
|
||
18 | * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
|
||
19 | * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
|
||
20 | * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
|
||
21 | * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
|
||
22 | * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
|
||
23 | * OTHER DEALINGS IN THE SOFTWARE.
|
||
24 | **/
|
||
25 | |||
26 | |||
27 | /**
|
||
28 | * @file i2c.c
|
||
29 | * @brief Implemenation of I2C communications protocol
|
||
30 | *
|
||
31 | * In the case where you have master sends and then a master request to the same
|
||
32 | * address, you will not give up control of the line because the send and
|
||
33 | * request addresses are seen as different addresses. In between it will send a
|
||
34 | * restart but will not give up the line.
|
||
35 | *
|
||
36 | * @author CMU Robotics Club, Kevin Woo, Sursh Nidhiry
|
||
37 | * @bug Not tested.
|
||
38 | */
|
||
39 | |||
40 | #include <avr/interrupt.h> |
||
41 | #include <util/twi.h> |
||
42 | |||
43 | #include "i2c.h" |
||
44 | #include "ring_buffer.h" |
||
45 | |||
46 | /**
|
||
47 | * @defgroup i2c I2C
|
||
48 | *
|
||
49 | * @brief Provides Inter-Interconnected-Communications (I2C)
|
||
50 | *
|
||
51 | * Initiates I2C functions on an ATMega128 which has a fully hardware Two Wire
|
||
52 | * Interface (TWI) module. Any Atmel chip with this hardware should be able to
|
||
53 | * use the software.
|
||
54 | *
|
||
55 | * This code will operate in a multi-master enviornment and can be either a
|
||
56 | * slave or a master at any time (as long as they are not one or the other at
|
||
57 | * the moment. You can queue up multiple transmission modes in the buffer up to
|
||
58 | * the buffer size. The buffer is implemented as a ring buffer.
|
||
59 | *
|
||
60 | * It is implemented using callback functions. Whenever you want to send a packet
|
||
61 | * you can call the built in send function (as a master) and it will send an array
|
||
62 | * of bytes. Master recieve and slave send/receive are all handled by the call back
|
||
63 | * functions. It is up to the end user to create functions that will handle the
|
||
64 | * receiving of packets. Their functions will be called with every byte recieved
|
||
65 | * so you must either buffer the inputs or handle each one separately.
|
||
66 | *
|
||
67 | * On errors we will simply flush the entire buffer.
|
||
68 | *
|
||
69 | * For information on how I2C operates, read the wikipedia article
|
||
70 | * http://en.wikipedia.org/wiki/I2c
|
||
71 | * for a good explanation of how it works.
|
||
72 | * @{
|
||
73 | */
|
||
74 | |||
75 | /**
|
||
76 | * @brief Set bit rate 12 = 100kbit/s (max speed setting is 10 for an
|
||
77 | * 8 MHz clock). It is a divider, so the lower the number the faster the speed.
|
||
78 | */
|
||
79 | #define I2C_BIT_RATE_DIVIDER 0x0C |
||
80 | |||
81 | static int start_flag; |
||
82 | |||
83 | static fun_mrecv_t master_recv_function;
|
||
84 | static fun_srecv_t slave_recv_function;
|
||
85 | static fun_send_t slave_send_function;
|
||
86 | |||
87 | RING_BUFFER_NEW(i2c_buffer, 128, char, i2c_write_buff, i2c_addr_buff); |
||
88 | |||
89 | |||
90 | /**
|
||
91 | * @brief Initializes the i2c module.
|
||
92 | *
|
||
93 | * Initializes the I2C module to start listening on the i2c lines. If the callback functions
|
||
94 | * are not set to null they will be called when that transmission mode is called. The address
|
||
95 | * is your address that you will listen to when you are not the master.
|
||
96 | *
|
||
97 | * @param addr Your address on the I2C bus.
|
||
98 | * @param master_recv The address of the function to call when you receive a byte when you are a
|
||
99 | * master.
|
||
100 | * @param slave_recv The address of the function to call when you are a slave you receive data
|
||
101 | * from the master
|
||
102 | * @param slave_send The address of the function to call when you are a slave and the master
|
||
103 | * requests data from you.
|
||
104 | *
|
||
105 | * @return 0 for success, nonzero for failure
|
||
106 | **/
|
||
107 | int i2c_init(char addr, fun_mrecv_t master_recv, fun_srecv_t slave_recv, fun_send_t slave_send) { |
||
108 | master_recv_function = master_recv; |
||
109 | slave_recv_function = slave_recv; |
||
110 | slave_send_function = slave_send; |
||
111 | |||
112 | RING_BUFFER_CLEAR(i2c_write_buff); |
||
113 | RING_BUFFER_CLEAR(i2c_addr_buff); |
||
114 | |||
115 | /* enables twi interrupt, automatic ack sending, and all twi hardware */
|
||
116 | TWCR = (_BV(TWEA) | _BV(TWEN) | _BV(TWIE)); |
||
117 | |||
118 | /* sets the bit rate of data transmission */
|
||
119 | TWBR = I2C_BIT_RATE_DIVIDER; |
||
120 | |||
121 | /* sets the address (it is stored in the 7 most significant bits) and allows
|
||
122 | * global messages to be accepted */
|
||
123 | TWAR = (addr << 1) | 1; |
||
124 | |||
125 | sei(); |
||
126 | |||
127 | return 0; |
||
128 | } |
||
129 | |||
130 | /**
|
||
131 | * @brief Sends a byte array over I2C as a master
|
||
132 | *
|
||
133 | * Will perform a send over I2C to the destination from data for the ammount of
|
||
134 | * bytes that bytes is.
|
||
135 | *
|
||
136 | * @param dest Destination address of the data on the I2C bus.
|
||
137 | * @param data The pointer to the byte array of data
|
||
138 | * @param bytes The amount of bytes long that the byte array is. This is how
|
||
139 | * many bytes from the array that the function will send.
|
||
140 | *
|
||
141 | * @return zero for success, nonzero for failure
|
||
142 | **/
|
||
143 | int i2c_send(char dest, char *data, size_t bytes) { |
||
144 | int i;
|
||
145 | |||
146 | /* adding data to be sent to ring buffers is not atomic,
|
||
147 | * so disable interrupts */
|
||
148 | cli(); |
||
149 | for(i = 0; i < bytes; i++) { |
||
150 | if(RING_BUFFER_FULL(i2c_write_buff)) {
|
||
151 | sei(); |
||
152 | return -1; |
||
153 | } |
||
154 | |||
155 | RING_BUFFER_ADD(i2c_write_buff, data[i]); |
||
156 | RING_BUFFER_ADD(i2c_addr_buff, dest << 1);
|
||
157 | } |
||
158 | |||
159 | /* re-enable the interrupts */
|
||
160 | sei(); |
||
161 | |||
162 | /* send the start bit, only if this device is not currently master */
|
||
163 | if(!start_flag) {
|
||
164 | start_flag = 1;
|
||
165 | TWCR |= _BV(TWSTA); |
||
166 | TWCR |= _BV(TWINT); |
||
167 | } |
||
168 | |||
169 | return 0; |
||
170 | } |
||
171 | |||
172 | /**
|
||
173 | * @brief Send a master request to the destination
|
||
174 | *
|
||
175 | * Sends a request of data from the target address and calls
|
||
176 | * the callback function to handle data as it comes in. This function will
|
||
177 | * not work if the slave has not informationt to send or has nothing implemented
|
||
178 | * to send it.
|
||
179 | *
|
||
180 | * @param dest The destination that we want to receive information from.
|
||
181 | *
|
||
182 | * @return 0 for success, nonzero for failure
|
||
183 | **/
|
||
184 | int i2c_request(char dest) { |
||
185 | if(RING_BUFFER_FULL(i2c_write_buff))
|
||
186 | return -1; |
||
187 | |||
188 | RING_BUFFER_ADD(i2c_write_buff, 0);
|
||
189 | RING_BUFFER_ADD(i2c_addr_buff, (dest << 1) | 1); |
||
190 | |||
191 | if(!start_flag) {
|
||
192 | start_flag = 1;
|
||
193 | TWCR |= _BV(TWSTA); |
||
194 | TWCR |= _BV(TWINT); |
||
195 | } |
||
196 | |||
197 | return 0; |
||
198 | } |
||
199 | |||
200 | /** @} **/
|
||
201 | |||
202 | /**
|
||
203 | * @brief Interrupt to handle I2C interrupts from the I2C hardware.
|
||
204 | *
|
||
205 | * Uses the status codes from the I2C register to handle the events
|
||
206 | * needed to advance in I2C stages. For instance, you will get a bit for
|
||
207 | * receiving a start ack, then a address ack, then a data ack, etc.
|
||
208 | * The events are handled in each switch case. The status codes are defined
|
||
209 | * by avr-gcc in /util/twi.h but are the same codes as the Atmel documentation.
|
||
210 | *
|
||
211 | * Bytes are sent by popping off the ring buffer. It also will keep track
|
||
212 | * of what modes the send is in.
|
||
213 | *
|
||
214 | * Errors are handled here as well.
|
||
215 | **/
|
||
216 | ISR(TWI_vect) { |
||
217 | static char data_to_send; |
||
218 | static char addr_to_send = -1; |
||
219 | char addr, statusCode;
|
||
220 | |||
221 | //Get status code (only upper 5 bits)
|
||
222 | statusCode = (TWSR & 0xF8);
|
||
223 | |||
224 | switch (statusCode) {
|
||
225 | //Start sent successfully
|
||
226 | case TW_START:
|
||
227 | case TW_REP_START:
|
||
228 | /* Send address and write
|
||
229 | * ring_buffer will not be empty */
|
||
230 | RING_BUFFER_REMOVE(i2c_addr_buff, addr_to_send); |
||
231 | RING_BUFFER_REMOVE(i2c_write_buff, data_to_send); |
||
232 | |||
233 | /* first send the address */
|
||
234 | TWDR = addr_to_send; |
||
235 | |||
236 | //Turn off start bits
|
||
237 | TWCR &= ~_BV(TWSTA); |
||
238 | break;
|
||
239 | |||
240 | //Master Transmit - Address sent succesfully
|
||
241 | case TW_MT_SLA_ACK:
|
||
242 | //Send byte
|
||
243 | TWDR = data_to_send; |
||
244 | //PORTG &= ~_BV(PG2);
|
||
245 | break;
|
||
246 | |||
247 | //Master Transmit - Data sent succesfully
|
||
248 | case TW_MT_DATA_ACK:
|
||
249 | //If there is still data to send
|
||
250 | if(!RING_BUFFER_EMPTY(i2c_write_buff)) {
|
||
251 | RING_BUFFER_PEEK(i2c_addr_buff, addr); |
||
252 | |||
253 | //Still data for this address
|
||
254 | if (addr == addr_to_send) {
|
||
255 | RING_BUFFER_REMOVE(i2c_addr_buff, addr); |
||
256 | RING_BUFFER_REMOVE(i2c_write_buff, TWDR); |
||
257 | break;
|
||
258 | //No more data for this address, data for another address -> resend start
|
||
259 | } else {
|
||
260 | TWCR |= _BV(TWSTA); |
||
261 | break;
|
||
262 | } |
||
263 | } |
||
264 | /* there are no bytes to send */
|
||
265 | TWCR |= _BV(TWSTO); |
||
266 | start_flag = 0;
|
||
267 | break;
|
||
268 | |||
269 | //Master Transmit - Slave sends a nack, transmit is done
|
||
270 | case TW_MT_DATA_NACK:
|
||
271 | //PORTG |= _BV(PG2);
|
||
272 | TWCR |= _BV(TWSTO); |
||
273 | start_flag = 0;
|
||
274 | break;
|
||
275 | |||
276 | //Master Receive - Address sent succesfully
|
||
277 | case TW_MR_SLA_ACK:
|
||
278 | //PORTG |= _BV(PG2);
|
||
279 | break;
|
||
280 | |||
281 | //Master Receive - Data received succesfully
|
||
282 | case TW_MR_DATA_ACK:
|
||
283 | if(master_recv_function) {
|
||
284 | if(!master_recv_function(TWDR)) {
|
||
285 | TWCR &= ~_BV(TWEA); |
||
286 | } |
||
287 | } |
||
288 | break;
|
||
289 | |||
290 | //Master Receive - Slave sends a nack, transmission is done
|
||
291 | case TW_MR_DATA_NACK:
|
||
292 | TWCR |= _BV(TWEA); |
||
293 | |||
294 | //If there is still data to send
|
||
295 | if(!RING_BUFFER_EMPTY(i2c_write_buff)) {
|
||
296 | TWCR |= _BV(TWSTA); |
||
297 | break;
|
||
298 | } |
||
299 | |||
300 | /* there are no bytes to send */
|
||
301 | TWCR |= _BV(TWSTO); |
||
302 | start_flag = 0;
|
||
303 | break;
|
||
304 | |||
305 | //Slave Transmit - Address received
|
||
306 | case TW_ST_SLA_ACK:
|
||
307 | break;
|
||
308 | |||
309 | //Slave Transmit - Nack received, no data requsted
|
||
310 | case TW_ST_DATA_NACK:
|
||
311 | break;
|
||
312 | |||
313 | //Slave Transmit - Data requested, ack received
|
||
314 | case TW_ST_DATA_ACK:
|
||
315 | if (slave_send_function) {
|
||
316 | TWDR = slave_send_function(); |
||
317 | } |
||
318 | break;
|
||
319 | |||
320 | //Slave Receive - Address received
|
||
321 | case TW_SR_SLA_ACK:
|
||
322 | break;
|
||
323 | |||
324 | //Slave Receive - Data received, ack returned
|
||
325 | case TW_SR_DATA_ACK:
|
||
326 | if(slave_recv_function) {
|
||
327 | slave_recv_function(TWDR); |
||
328 | } |
||
329 | |||
330 | break;
|
||
331 | |||
332 | //Stop sent
|
||
333 | case TW_SR_STOP:
|
||
334 | break;
|
||
335 | |||
336 | //Problem on the bus, reset everything
|
||
337 | default:
|
||
338 | TWCR |= _BV(TWSTO); |
||
339 | start_flag = 0;
|
||
340 | RING_BUFFER_CLEAR(i2c_write_buff); |
||
341 | RING_BUFFER_CLEAR(i2c_addr_buff); |
||
342 | } |
||
343 | |||
344 | /* Toggle TWINT so that it resets and executes the commands */
|
||
345 | TWCR |= _BV(TWINT); |
||
346 | } |