逻辑电平转换
树莓派的逻辑电平为3.3v，Arduino为5v，需要进行逻辑转换，在某宝买了个逻辑转换器：
HV接5V电源
LV接3.3V电源
GND接电源负极，两个电源公地
RXI输入5v TTL，将在RXO输出3.3v TTL
TXI输入输出3.3V TTL ，TXO输入输出5V TTL， TXI与TXO双向互转
连线方式
树莓派的程序
1 /*
2 * SPI testing utility (using spidev driver)
3 *
4 * Copyright (c) 2007 MontaVista Software, Inc.
5 * Copyright (c) 2007 Anton Vorontsov <[email protected]>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License.
10 *
11 * Cross-compile with cross-gcc -I/path/to/cross-kernel/include
12 */
13
14 #include <stdint.h>
15 #include <unistd.h>
16 #include <stdio.h>
17 #include <stdlib.h>
18 #include <getopt.h>
19 #include <fcntl.h>
20 #include <sys/ioctl.h>
21 #include <linux/types.h>
22 #include <linux/spi/spidev.h>
23
24 #define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
25
26 static void pabort(const char *s)
27 {
28 perror(s);
29 abort();
30 }
31
32 static const char *device = "/dev/spidev0.0";
33 static uint8_t mode;
34 static uint8_t bits = 8;
35 static uint32_t speed = 500000;
36 static uint16_t delay;
37
38 static void transfer(int fd)
39 {
40 int ret;
41 uint8_t tx[] = {
42 0x48, 0x45, 0x4C, 0x4C, 0x4F,
43 0x20,
44 0x57, 0x4F, 0x52, 0x4C, 0x44,
45 0x0A
46 };
47 uint8_t rx[ARRAY_SIZE(tx)] = {0, };
48 struct spi_ioc_transfer tr = {
49 .tx_buf = (unsigned long)tx,
50 .rx_buf = (unsigned long)rx,
51 .len = ARRAY_SIZE(tx),
52 .delay_usecs = delay,
53 .speed_hz = speed,
54 .bits_per_word = bits,
55 };
56
57 ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr);
58 if (ret < 1)
59 pabort("can‘t send spi message");
60
61 /*
62 for (ret = 0; ret < ARRAY_SIZE(tx); ret++) {
63 if (!(ret % 6))
64 puts("");
65 printf("%.2X ", rx[ret]);
66 }
67 puts("");
68 */
69 }
70
71 static void print_usage(const char *prog)
72 {
73 printf("Usage: %s [-DsbdlHOLC3]\n", prog);
74 puts(" -D --device device to use (default /dev/spidev1.1)\n"
75 " -s --speed max speed (Hz)\n"
76 " -d --delay delay (usec)\n"
77 " -b --bpw bits per word \n"
78 " -l --loop loopback\n"
79 " -H --cpha clock phase\n"
80 " -O --cpol clock polarity\n"
81 " -L --lsb least significant bit first\n"
82 " -C --cs-high chip select active high\n"
83 " -3 --3wire SI/SO signals shared\n");
84 exit(1);
85 }
86
87 static void parse_opts(int argc, char *argv[])
88 {
89 while (1) {
90 static const struct option lopts[] = {
91 { "device", 1, 0, ‘D‘ },
92 { "speed", 1, 0, ‘s‘ },
93 { "delay", 1, 0, ‘d‘ },
94 { "bpw", 1, 0, ‘b‘ },
95 { "loop", 0, 0, ‘l‘ },
96 { "cpha", 0, 0, ‘H‘ },
97 { "cpol", 0, 0, ‘O‘ },
98 { "lsb", 0, 0, ‘L‘ },
99 { "cs-high", 0, 0, ‘C‘ },
100 { "3wire", 0, 0, ‘3‘ },
101 { "no-cs", 0, 0, ‘N‘ },
102 { "ready", 0, 0, ‘R‘ },
103 { NULL, 0, 0, 0 },
104 };
105 int c;
106
107 c = getopt_long(argc, argv, "D:s:d:b:lHOLC3NR", lopts, NULL);
108
109 if (c == -1)
110 break;
111
112 switch (c) {
113 case ‘D‘:
114 device = optarg;
115 break;
116 case ‘s‘:
117 speed = atoi(optarg);
118 break;
119 case ‘d‘:
120 delay = atoi(optarg);
121 break;
122 case ‘b‘:
123 bits = atoi(optarg);
124 break;
125 case ‘l‘:
126 mode |= SPI_LOOP;
127 break;
128 case ‘H‘:
129 mode |= SPI_CPHA;
130 break;
131 case ‘O‘:
132 mode |= SPI_CPOL;
133 break;
134 case ‘L‘:
135 mode |= SPI_LSB_FIRST;
136 break;
137 case ‘C‘:
138 mode |= SPI_CS_HIGH;
139 break;
140 case ‘3‘:
141 mode |= SPI_3WIRE;
142 break;
143 case ‘N‘:
144 mode |= SPI_NO_CS;
145 break;
146 case ‘R‘:
147 mode |= SPI_READY;
148 break;
149 default:
150 print_usage(argv[0]);
151 break;
152 }
153 }
154 }
155
156 int main(int argc, char *argv[])
157 {
158 int ret = 0;
159 int fd;
160
161 parse_opts(argc, argv);
162
163 fd = open(device, O_RDWR);
164 if (fd < 0)
165 pabort("can‘t open device");
166
167 /*
168 * spi mode
169 */
170 ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);
171 if (ret == -1)
172 pabort("can‘t set spi mode");
173
174 ret = ioctl(fd, SPI_IOC_RD_MODE, &mode);
175 if (ret == -1)
176 pabort("can‘t get spi mode");
177
178 /*
179 * bits per word
180 */
181 ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);
182 if (ret == -1)
183 pabort("can‘t set bits per word");
184
185 ret = ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits);
186 if (ret == -1)
187 pabort("can‘t get bits per word");
188
189 /*
190 * max speed hz
191 */
192 ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed);
193 if (ret == -1)
194 pabort("can‘t set max speed hz");
195
196 ret = ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed);
197 if (ret == -1)
198 pabort("can‘t get max speed hz");
199
200 printf("spi mode: %d\n", mode);
201 printf("bits per word: %d\n", bits);
202 printf("max speed: %d Hz (%d KHz)\n", speed, speed/1000);
203
204 transfer(fd);
205
206 close(fd);
207
208 return ret;
209 }
Arduino的程序
1 // Written by Nick Gammon
2 // February 2011
3
4
5 #include <SPI.h>
6
7 char buf [100];
8 volatile byte pos;
9 volatile boolean process_it;
10
11 void setup (void)
12 {
13 Serial.begin (115200); // debugging
14
15 // have to send on master in, *slave out*
16 pinMode(MISO, OUTPUT);
17
18 // turn on SPI in slave mode
19 SPCR |= _BV(SPE);
20
21 // get ready for an interrupt
22 pos = 0; // buffer empty
23 process_it = false;
24
25 // now turn on interrupts
26 SPI.attachInterrupt();
27
28 } // end of setup
29
30
31 // SPI interrupt routine
32 ISR (SPI_STC_vect)
33 {
34 byte c = SPDR; // grab byte from SPI Data Register
35
36 // add to buffer if room
37 if (pos < sizeof buf)
38 {
39 buf [pos++] = c;
40
41 // example: newline means time to process buffer
42 if (c == ‘\n‘)
43 process_it = true;
44
45 } // end of room available
46 } // end of interrupt routine SPI_STC_vect
47
48 // main loop - wait for flag set in interrupt routine
49 void loop (void)
50 {
51 if (process_it)
52 {
53 buf [pos] = 0;
54 Serial.println (buf);
55 pos = 0;
56 process_it = false;
57 } // end of flag set
58
59 } // end of loopang
时间： 2024-10-10 14:49:26