1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
|
/*
* Copyright © 2011 Keith Packard <keithp@keithp.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
#include "ao.h"
uint8_t
ao_spi_slave_recv(void *buf, uint16_t len)
{
uint8_t *b = buf;
while (len--) {
while (!(SPSR & (1 << SPIF)))
if ((PINB & (1 << PINB0)))
return 0;
*b++ = SPDR;
}
return 1;
}
void
ao_spi_slave_send(void *buf, uint16_t len)
{
uint8_t *b = buf;
while (len--) {
SPDR = *b++;
while (!(SPSR & (1 << SPIF)))
if ((PINB & (1 << PINB0)))
return;
}
/* Clear pending SPIF bit by reading */
(void) SPDR;
}
static uint8_t ao_spi_slave_running;
ISR(PCINT0_vect, ISR_BLOCK)
{
#if SPI_SLAVE_PIN_0_3
if ((PINB & (1 << PORTB0)) == 0)
#endif
#if SPI_SLAVE_PIN_2_5
if ((PINB & (1 << PORTB2)) == 0)
#endif
{
if (!ao_spi_slave_running) {
ao_spi_slave_running = 1;
ao_spi_slave();
}
} else {
ao_spi_slave_running = 0;
}
}
void
ao_spi_slave_init(void)
{
/* We'd like to have a pull-up on SS so that disconnecting the
* TM would cause any SPI transaction to abort. However, when
* I tried that, SPI transactions would spontaneously abort,
* making me assume that we needed a less aggressive pull-up
* than is offered inside the AVR
*/
#if SPI_SLAVE_PIN_0_3
PCMSK0 |= (1 << PCINT0); /* Enable PCINT0 pin change */
PCICR |= (1 << PCIE0); /* Enable pin change interrupt */
DDRB = ((DDRB & 0xf0) |
(1 << 3) | /* MISO, output */
(0 << 2) | /* MOSI, input */
(0 << 1) | /* SCK, input */
(0 << 0)); /* SS, input */
PORTB = ((PORTB & 0xf0) |
(1 << 3) | /* MISO, output */
(0 << 2) | /* MOSI, no pull-up */
(0 << 1) | /* SCK, no pull-up */
(1 << 0)); /* SS, pull-up */
#endif
#if SPI_SLAVE_PIN_2_5
PCMSK0 |= (1 << PCINT2); /* Enable PCINT2 pin change */
PCICR |= (1 << PCIE0); /* Enable pin change interrupt */
DDRB = ((DDRB & 0xf0) |
(0 << 5) | /* SCK, input */
(1 << 4) | /* MISO, output */
(0 << 3) | /* MOSI, input */
(0 << 2)); /* SS, input */
PORTB = ((PORTB & 0xf0) |
(0 << 5) | /* SCK, no pull-up */
(1 << 4) | /* MISO, output */
(0 << 3) | /* MOSI, no pull-up */
(1 << 2)); /* SS, pull-up */
#endif
SPCR = (0 << SPIE) | /* Disable SPI interrupts */
(1 << SPE) | /* Enable SPI */
(0 << DORD) | /* MSB first */
(0 << MSTR) | /* Slave mode */
(0 << CPOL) | /* Clock low when idle */
(0 << CPHA); /* Sample at leading clock edge */
}
|
