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-rw-r--r--drivers/avr/TWIlib.c232
1 files changed, 232 insertions, 0 deletions
diff --git a/drivers/avr/TWIlib.c b/drivers/avr/TWIlib.c
new file mode 100644
index 000000000..b39e3054a
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+++ b/drivers/avr/TWIlib.c
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1/*
2 * TWIlib.c
3 *
4 * Created: 6/01/2014 10:41:33 PM
5 * Author: Chris Herring
6 * http://www.chrisherring.net/all/tutorial-interrupt-driven-twi-interface-for-avr-part1/
7 */
8
9#include <avr/io.h>
10#include <avr/interrupt.h>
11#include "TWIlib.h"
12#include "util/delay.h"
13
14void TWIInit()
15{
16 TWIInfo.mode = Ready;
17 TWIInfo.errorCode = 0xFF;
18 TWIInfo.repStart = 0;
19 // Set pre-scalers (no pre-scaling)
20 TWSR = 0;
21 // Set bit rate
22 TWBR = ((F_CPU / TWI_FREQ) - 16) / 2;
23 // Enable TWI and interrupt
24 TWCR = (1 << TWIE) | (1 << TWEN);
25}
26
27uint8_t isTWIReady()
28{
29 if ( (TWIInfo.mode == Ready) | (TWIInfo.mode == RepeatedStartSent) )
30 {
31 return 1;
32 }
33 else
34 {
35 return 0;
36 }
37}
38
39uint8_t TWITransmitData(void *const TXdata, uint8_t dataLen, uint8_t repStart)
40{
41 if (dataLen <= TXMAXBUFLEN)
42 {
43 // Wait until ready
44 while (!isTWIReady()) {_delay_us(1);}
45 // Set repeated start mode
46 TWIInfo.repStart = repStart;
47 // Copy data into the transmit buffer
48 uint8_t *data = (uint8_t *)TXdata;
49 for (int i = 0; i < dataLen; i++)
50 {
51 TWITransmitBuffer[i] = data[i];
52 }
53 // Copy transmit info to global variables
54 TXBuffLen = dataLen;
55 TXBuffIndex = 0;
56
57 // If a repeated start has been sent, then devices are already listening for an address
58 // and another start does not need to be sent.
59 if (TWIInfo.mode == RepeatedStartSent)
60 {
61 TWIInfo.mode = Initializing;
62 TWDR = TWITransmitBuffer[TXBuffIndex++]; // Load data to transmit buffer
63 TWISendTransmit(); // Send the data
64 }
65 else // Otherwise, just send the normal start signal to begin transmission.
66 {
67 TWIInfo.mode = Initializing;
68 TWISendStart();
69 }
70
71 }
72 else
73 {
74 return 1; // return an error if data length is longer than buffer
75 }
76 return 0;
77}
78
79uint8_t TWIReadData(uint8_t TWIaddr, uint8_t bytesToRead, uint8_t repStart)
80{
81 // Check if number of bytes to read can fit in the RXbuffer
82 if (bytesToRead < RXMAXBUFLEN)
83 {
84 // Reset buffer index and set RXBuffLen to the number of bytes to read
85 RXBuffIndex = 0;
86 RXBuffLen = bytesToRead;
87 // Create the one value array for the address to be transmitted
88 uint8_t TXdata[1];
89 // Shift the address and AND a 1 into the read write bit (set to write mode)
90 TXdata[0] = (TWIaddr << 1) | 0x01;
91 // Use the TWITransmitData function to initialize the transfer and address the slave
92 TWITransmitData(TXdata, 1, repStart);
93 }
94 else
95 {
96 return 0;
97 }
98 return 1;
99}
100
101ISR (TWI_vect)
102{
103 switch (TWI_STATUS)
104 {
105 // ----\/ ---- MASTER TRANSMITTER OR WRITING ADDRESS ----\/ ---- //
106 case TWI_MT_SLAW_ACK: // SLA+W transmitted and ACK received
107 // Set mode to Master Transmitter
108 TWIInfo.mode = MasterTransmitter;
109 case TWI_START_SENT: // Start condition has been transmitted
110 case TWI_MT_DATA_ACK: // Data byte has been transmitted, ACK received
111 if (TXBuffIndex < TXBuffLen) // If there is more data to send
112 {
113 TWDR = TWITransmitBuffer[TXBuffIndex++]; // Load data to transmit buffer
114 TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
115 TWISendTransmit(); // Send the data
116 }
117 // This transmission is complete however do not release bus yet
118 else if (TWIInfo.repStart)
119 {
120 TWIInfo.errorCode = 0xFF;
121 TWISendStart();
122 }
123 // All transmissions are complete, exit
124 else
125 {
126 TWIInfo.mode = Ready;
127 TWIInfo.errorCode = 0xFF;
128 TWISendStop();
129 }
130 break;
131
132 // ----\/ ---- MASTER RECEIVER ----\/ ---- //
133
134 case TWI_MR_SLAR_ACK: // SLA+R has been transmitted, ACK has been received
135 // Switch to Master Receiver mode
136 TWIInfo.mode = MasterReceiver;
137 // If there is more than one byte to be read, receive data byte and return an ACK
138 if (RXBuffIndex < RXBuffLen-1)
139 {
140 TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
141 TWISendACK();
142 }
143 // Otherwise when a data byte (the only data byte) is received, return NACK
144 else
145 {
146 TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
147 TWISendNACK();
148 }
149 break;
150
151 case TWI_MR_DATA_ACK: // Data has been received, ACK has been transmitted.
152
153 /// -- HANDLE DATA BYTE --- ///
154 TWIReceiveBuffer[RXBuffIndex++] = TWDR;
155 // If there is more than one byte to be read, receive data byte and return an ACK
156 if (RXBuffIndex < RXBuffLen-1)
157 {
158 TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
159 TWISendACK();
160 }
161 // Otherwise when a data byte (the only data byte) is received, return NACK
162 else
163 {
164 TWIInfo.errorCode = TWI_NO_RELEVANT_INFO;
165 TWISendNACK();
166 }
167 break;
168
169 case TWI_MR_DATA_NACK: // Data byte has been received, NACK has been transmitted. End of transmission.
170
171 /// -- HANDLE DATA BYTE --- ///
172 TWIReceiveBuffer[RXBuffIndex++] = TWDR;
173 // This transmission is complete however do not release bus yet
174 if (TWIInfo.repStart)
175 {
176 TWIInfo.errorCode = 0xFF;
177 TWISendStart();
178 }
179 // All transmissions are complete, exit
180 else
181 {
182 TWIInfo.mode = Ready;
183 TWIInfo.errorCode = 0xFF;
184 TWISendStop();
185 }
186 break;
187
188 // ----\/ ---- MT and MR common ----\/ ---- //
189
190 case TWI_MR_SLAR_NACK: // SLA+R transmitted, NACK received
191 case TWI_MT_SLAW_NACK: // SLA+W transmitted, NACK received
192 case TWI_MT_DATA_NACK: // Data byte has been transmitted, NACK received
193 case TWI_LOST_ARBIT: // Arbitration has been lost
194 // Return error and send stop and set mode to ready
195 if (TWIInfo.repStart)
196 {
197 TWIInfo.errorCode = TWI_STATUS;
198 TWISendStart();
199 }
200 // All transmissions are complete, exit
201 else
202 {
203 TWIInfo.mode = Ready;
204 TWIInfo.errorCode = TWI_STATUS;
205 TWISendStop();
206 }
207 break;
208 case TWI_REP_START_SENT: // Repeated start has been transmitted
209 // Set the mode but DO NOT clear TWINT as the next data is not yet ready
210 TWIInfo.mode = RepeatedStartSent;
211 break;
212
213 // ----\/ ---- SLAVE RECEIVER ----\/ ---- //
214
215 // TODO IMPLEMENT SLAVE RECEIVER FUNCTIONALITY
216
217 // ----\/ ---- SLAVE TRANSMITTER ----\/ ---- //
218
219 // TODO IMPLEMENT SLAVE TRANSMITTER FUNCTIONALITY
220
221 // ----\/ ---- MISCELLANEOUS STATES ----\/ ---- //
222 case TWI_NO_RELEVANT_INFO: // It is not really possible to get into this ISR on this condition
223 // Rather, it is there to be manually set between operations
224 break;
225 case TWI_ILLEGAL_START_STOP: // Illegal START/STOP, abort and return error
226 TWIInfo.errorCode = TWI_ILLEGAL_START_STOP;
227 TWIInfo.mode = Ready;
228 TWISendStop();
229 break;
230 }
231
232}
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