root / trunk / code / projects / libdragonfly / i2c.c @ 1452
History | View | Annotate | Download (11 KB)
1 |
/**
|
---|---|
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 |
return 0; |
126 |
} |
127 |
|
128 |
/**
|
129 |
* @brief Sends a byte array over I2C as a master
|
130 |
*
|
131 |
* Will perform a send over I2C to the destination from data for the ammount of
|
132 |
* bytes that bytes is.
|
133 |
*
|
134 |
* @param dest Destination address of the data on the I2C bus.
|
135 |
* @param data The pointer to the byte array of data
|
136 |
* @param bytes The amount of bytes long that the byte array is. This is how
|
137 |
* many bytes from the array that the function will send.
|
138 |
*
|
139 |
* @return zero for success, nonzero for failure
|
140 |
**/
|
141 |
int i2c_send(char dest, char *data, unsigned int bytes) { |
142 |
int i;
|
143 |
|
144 |
/* adding data to be sent to ring buffers is not atomic,
|
145 |
* so disable interrupts */
|
146 |
cli(); |
147 |
for(i = 0; i < bytes; i++) { |
148 |
if(RING_BUFFER_FULL(i2c_write_buff)) {
|
149 |
sei(); |
150 |
return -1; |
151 |
} |
152 |
|
153 |
RING_BUFFER_ADD(i2c_write_buff, data[i]); |
154 |
RING_BUFFER_ADD(i2c_addr_buff, dest << 1);
|
155 |
} |
156 |
|
157 |
/* re-enable the interrupts */
|
158 |
sei(); |
159 |
|
160 |
/* send the start bit, only if this device is not currently master */
|
161 |
if(!start_flag) {
|
162 |
start_flag = 1;
|
163 |
TWCR |= _BV(TWSTA); |
164 |
TWCR |= _BV(TWINT); |
165 |
} |
166 |
|
167 |
return 0; |
168 |
} |
169 |
|
170 |
/**
|
171 |
* @brief Send a master request to the destination
|
172 |
*
|
173 |
* Sends a request of data from the target address and calls
|
174 |
* the callback function to handle data as it comes in. This function will
|
175 |
* not work if the slave has not informationt to send or has nothing implemented
|
176 |
* to send it.
|
177 |
*
|
178 |
* @param dest The destination that we want to receive information from.
|
179 |
*
|
180 |
* @return 0 for success, nonzero for failure
|
181 |
**/
|
182 |
int i2c_request(char dest) { |
183 |
if(RING_BUFFER_FULL(i2c_write_buff))
|
184 |
return -1; |
185 |
|
186 |
RING_BUFFER_ADD(i2c_write_buff, 0);
|
187 |
RING_BUFFER_ADD(i2c_addr_buff, (dest << 1) | 1); |
188 |
|
189 |
if(!start_flag) {
|
190 |
start_flag = 1;
|
191 |
TWCR |= _BV(TWSTA); |
192 |
TWCR |= _BV(TWINT); |
193 |
} |
194 |
|
195 |
return 0; |
196 |
} |
197 |
|
198 |
/** @} **/
|
199 |
|
200 |
/**
|
201 |
* @brief Interrupt to handle I2C interrupts from the I2C hardware.
|
202 |
*
|
203 |
* Uses the status codes from the I2C register to handle the events
|
204 |
* needed to advance in I2C stages. For instance, you will get a bit for
|
205 |
* receiving a start ack, then a address ack, then a data ack, etc.
|
206 |
* The events are handled in each switch case. The status codes are defined
|
207 |
* by avr-gcc in /util/twi.h but are the same codes as the Atmel documentation.
|
208 |
*
|
209 |
* Bytes are sent by popping off the ring buffer. It also will keep track
|
210 |
* of what modes the send is in.
|
211 |
*
|
212 |
* Errors are handled here as well.
|
213 |
**/
|
214 |
ISR(TWI_vect) { |
215 |
static char data_to_send; |
216 |
static char addr_to_send = -1; |
217 |
char addr, statusCode;
|
218 |
|
219 |
//Get status code (only upper 5 bits)
|
220 |
statusCode = (TWSR & 0xF8);
|
221 |
|
222 |
switch (statusCode) {
|
223 |
//Start sent successfully
|
224 |
case TW_START:
|
225 |
case TW_REP_START:
|
226 |
/* Send address and write
|
227 |
* ring_buffer will not be empty */
|
228 |
RING_BUFFER_REMOVE(i2c_addr_buff, addr_to_send); |
229 |
RING_BUFFER_REMOVE(i2c_write_buff, data_to_send); |
230 |
|
231 |
/* first send the address */
|
232 |
TWDR = addr_to_send; |
233 |
|
234 |
//Turn off start bits
|
235 |
TWCR &= ~_BV(TWSTA); |
236 |
break;
|
237 |
|
238 |
//Master Transmit - Address sent succesfully
|
239 |
case TW_MT_SLA_ACK:
|
240 |
//Send byte
|
241 |
TWDR = data_to_send; |
242 |
PORTG &= ~_BV(PG2); |
243 |
break;
|
244 |
|
245 |
//Master Transmit - Data sent succesfully
|
246 |
case TW_MT_DATA_ACK:
|
247 |
//If there is still data to send
|
248 |
if(!RING_BUFFER_EMPTY(i2c_write_buff)) {
|
249 |
RING_BUFFER_PEEK(i2c_addr_buff, addr); |
250 |
|
251 |
//Still data for this address
|
252 |
if (addr == addr_to_send) {
|
253 |
RING_BUFFER_REMOVE(i2c_addr_buff, addr); |
254 |
RING_BUFFER_REMOVE(i2c_write_buff, TWDR); |
255 |
break;
|
256 |
//No more data for this address, data for another address -> resend start
|
257 |
} else {
|
258 |
TWCR |= _BV(TWSTA); |
259 |
break;
|
260 |
} |
261 |
} |
262 |
/* there are no bytes to send */
|
263 |
TWCR |= _BV(TWSTO); |
264 |
start_flag = 0;
|
265 |
break;
|
266 |
|
267 |
//Master Transmit - Slave sends a nack, transmit is done
|
268 |
case TW_MT_DATA_NACK:
|
269 |
PORTG |= _BV(PG2); |
270 |
TWCR |= _BV(TWSTO); |
271 |
start_flag = 0;
|
272 |
break;
|
273 |
|
274 |
//Master Receive - Address sent succesfully
|
275 |
case TW_MR_SLA_ACK:
|
276 |
PORTG |= _BV(PG2); |
277 |
break;
|
278 |
|
279 |
//Master Receive - Data received succesfully
|
280 |
case TW_MR_DATA_ACK:
|
281 |
if(master_recv_function) {
|
282 |
if(!master_recv_function(TWDR)) {
|
283 |
TWCR &= ~_BV(TWEA); |
284 |
} |
285 |
} |
286 |
break;
|
287 |
|
288 |
//Master Receive - Slave sends a nack, transmission is done
|
289 |
case TW_MR_DATA_NACK:
|
290 |
TWCR |= _BV(TWEA); |
291 |
|
292 |
//If there is still data to send
|
293 |
if(!RING_BUFFER_EMPTY(i2c_write_buff)) {
|
294 |
TWCR |= _BV(TWSTA); |
295 |
break;
|
296 |
} |
297 |
|
298 |
/* there are no bytes to send */
|
299 |
TWCR |= _BV(TWSTO); |
300 |
start_flag = 0;
|
301 |
break;
|
302 |
|
303 |
//Slave Transmit - Address received
|
304 |
case TW_ST_SLA_ACK:
|
305 |
break;
|
306 |
|
307 |
//Slave Transmit - Nack received, no data requsted
|
308 |
case TW_ST_DATA_NACK:
|
309 |
break;
|
310 |
|
311 |
//Slave Transmit - Data requested, ack received
|
312 |
case TW_ST_DATA_ACK:
|
313 |
if (slave_send_function) {
|
314 |
TWDR = slave_send_function(); |
315 |
} |
316 |
break;
|
317 |
|
318 |
//Slave Receive - Address received
|
319 |
case TW_SR_SLA_ACK:
|
320 |
break;
|
321 |
|
322 |
//Slave Receive - Data received, ack returned
|
323 |
case TW_SR_DATA_ACK:
|
324 |
if(slave_recv_function) {
|
325 |
slave_recv_function(TWDR); |
326 |
} |
327 |
|
328 |
break;
|
329 |
|
330 |
//Stop sent
|
331 |
case TW_SR_STOP:
|
332 |
break;
|
333 |
|
334 |
//Problem on the bus, reset everything
|
335 |
default:
|
336 |
TWCR |= _BV(TWSTO); |
337 |
start_flag = 0;
|
338 |
RING_BUFFER_CLEAR(i2c_write_buff); |
339 |
RING_BUFFER_CLEAR(i2c_addr_buff); |
340 |
} |
341 |
|
342 |
/* Toggle TWINT so that it resets and executes the commands */
|
343 |
TWCR |= _BV(TWINT); |
344 |
} |
345 |
|