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/*
* 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"
/*
* Atmega32u4 USART in MSPIM (master SPI mode)
*/
__xdata uint8_t ao_spi_mutex;
/* Send bytes over SPI.
*
* This just polls; the SPI is set to go as fast as possible,
* so using interrupts would take way too long
*/
void
ao_spi_send_bus(void __xdata *block, uint16_t len) __reentrant
{
uint8_t *d = block;
while (len--) {
while (!(UCSR1A & (1 << UDRE1)));
UDR1 = *d++;
while (!(UCSR1A & (1 << RXC1)));
(void) UDR1;
}
}
/* Receive bytes over SPI.
*
* Poll, sending zeros and reading data back
*/
void
ao_spi_recv_bus(void __xdata *block, uint16_t len) __reentrant
{
uint8_t *d = block;
/* Clear any pending data */
while (UCSR1A & (1 << RXC1))
(void) UDR1;
while (len--) {
while (!(UCSR1A & (1 << UDRE1)));
UDR1 = 0;
while (!(UCSR1A & (1 << RXC1)));
*d++ = UDR1;
}
}
/*
* Initialize USART0 for SPI using config alt 2
*
* MO P1_5
* MI P1_4
* CLK P1_3
*
* Chip select is the responsibility of the caller
*/
#define XCK1_DDR DDRD
#define XCK1_PORT PORTD
#define XCK1 PORTD5
#define XMS1_DDR DDRE
#define XMS1_PORT PORTE
#define XMS1 PORTE6
void
ao_spi_init(void)
{
/* Ensure the USART is powered */
PRR1 &= ~(1 << PRUSART1);
/*
* Set pin directions
*/
XCK1_DDR |= (1 << XCK1);
/* Clear chip select (which is negated) */
XMS1_PORT |= (1 < XMS1);
XMS1_DDR |= (1 << XMS1);
/* Set baud register to zero (required before turning transmitter on) */
UBRR1 = 0;
UCSR1C = ((0x3 << UMSEL10) | /* Master SPI mode */
(0 << UCSZ10) | /* SPI mode 0 */
(0 << UCPOL1)); /* SPI mode 0 */
/* Enable transmitter and receiver */
UCSR1B = ((1 << RXEN1) |
(1 << TXEN1));
/* It says that 0 is a legal value; we'll see... */
UBRR1 = 0;
}
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