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7fd9044d94
This decreases the retrieval time for a frame of 102 bytes from 660 us to 384 us, corresponding to a speed change from about 1.26 Mbps to 2.17 Mbps (102 bytes plus 2 bytes overhead).
89 lines
1.4 KiB
C
89 lines
1.4 KiB
C
/*
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* fw/spi.c - ATmega8 family SPI I/O
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*
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* Written 2011, 2013 by Werner Almesberger
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* Copyright 2011, 2013 Werner Almesberger
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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#include <stdbool.h>
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#include <stdint.h>
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#include <avr/io.h>
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#include "board.h"
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#include "spi.h"
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static bool spi_initialized = 0;
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void spi_begin(void)
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{
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if (!spi_initialized)
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spi_init();
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CLR(nSS);
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}
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uint8_t spi_io(uint8_t v)
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{
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// while (!(UCSR1A & 1 << UDRE1));
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UDR1 = v;
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while (!(UCSR1A & 1 << RXC1));
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return UDR1;
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}
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void spi_end(void)
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{
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// while (!(UCSR1A & 1 << TXC1));
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SET(nSS);
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}
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void spi_recv_block(uint8_t *buf, uint8_t n)
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{
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if (!n)
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return;
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UDR1 = 0;
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while (--n) {
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while (!(UCSR1A & 1 << RXC1));
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*buf++ = UDR1;
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UDR1 = 0;
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}
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while (!(UCSR1A & 1 << RXC1));
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*buf++ = UDR1;
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}
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void spi_off(void)
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{
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spi_initialized = 0;
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UCSR1B = 0;
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}
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void spi_init(void)
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{
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SET(nSS);
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OUT(SCLK);
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OUT(MOSI);
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OUT(nSS);
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IN(MISO);
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UBRR1 = 0; /* set bit rate to zero to begin */
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UCSR1C = 1 << UMSEL11 | 1 << UMSEL10;
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/* set MSPI, MSB first, SPI data mode 0 */
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UCSR1B = 1 << RXEN1 | 1 << TXEN1;
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/* enable receiver and transmitter */
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UBRR1 = 0; /* reconfirm the bit rate */
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spi_initialized = 1;
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}
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