2 * Copyright © 2011 Keith Packard <keithp@keithp.com>
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
14 * You should have received a copy of the GNU General Public License along
15 * with this program; if not, write to the Free Software Foundation, Inc.,
16 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
22 * Atmega32u4 USART in MSPIM (master SPI mode)
25 __xdata uint8_t ao_spi_mutex;
27 /* Send bytes over SPI.
29 * This just polls; the SPI is set to go as fast as possible,
30 * so using interrupts would take way too long
33 ao_spi_send_bus(void __xdata *block, uint16_t len) __reentrant
38 while (!(UCSR1A & (1 << UDRE1)));
40 while (!(UCSR1A & (1 << RXC1)));
45 /* Receive bytes over SPI.
47 * Poll, sending zeros and reading data back
50 ao_spi_recv_bus(void __xdata *block, uint16_t len) __reentrant
54 /* Clear any pending data */
55 while (UCSR1A & (1 << RXC1))
59 while (!(UCSR1A & (1 << UDRE1)));
61 while (!(UCSR1A & (1 << RXC1)));
67 * Initialize USART0 for SPI using config alt 2
73 * Chip select is the responsibility of the caller
77 #define XCK1_PORT PORTD
80 #define XMS1_PORT PORTE
86 /* Ensure the USART is powered */
87 PRR1 &= ~(1 << PRUSART1);
92 XCK1_DDR |= (1 << XCK1);
94 /* Clear chip select (which is negated) */
95 XMS1_PORT |= (1 < XMS1);
96 XMS1_DDR |= (1 << XMS1);
98 /* Set baud register to zero (required before turning transmitter on) */
101 UCSR1C = ((0x3 << UMSEL10) | /* Master SPI mode */
102 (0 << UCSZ10) | /* SPI mode 0 */
103 (0 << UCPOL1)); /* SPI mode 0 */
105 /* Enable transmitter and receiver */
106 UCSR1B = ((1 << RXEN1) |
109 /* It says that 0 is a legal value; we'll see... */