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99 lines
2.1 KiB
C
99 lines
2.1 KiB
C
/*
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* fw/led.c - LED control
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*
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* Written 2012 by Werner Almesberger
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* Copyright 2012 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 <stdint.h>
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include <avr/pgmspace.h>
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#define F_CPU 8000000UL
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#include <util/delay.h>
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#include "io.h"
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#include "led.h"
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void led_show(const uint8_t p[LED_BYTES])
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{
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uint8_t i;
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for (i = 0; i != LED_BYTES; i++) {
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while (!(UCSR0A & (1 << UDRE0)));
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UDR0 = p[i];
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}
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/*
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* There doesn't seem to be any reliable way to synchronize with the
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* end of the shift operation register that wouldn't cli/sei. Note
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* that, since the receiver is disabled, we can't use the RX side for
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* this purpose (as it is done in the atusb firmware).
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*
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* So instead we just wait for the worst-case delay, being one byte
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* in the shift register and another byte in the transmit buffer,
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* giving a total of 16 bits.
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*
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* This is a bit too pessimistic and produces a slight extra delay of
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* about 1.8 us. (The whole pattern transmission takes 16 us.)
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* See also ../doc/lclk-1123.png
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*/
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_delay_us(4); /* 16 bits at 4 MHz */
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SET(LED_LCLK);
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CLR(LED_LCLK);
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}
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void led_show_pgm(const prog_uint8_t p[LED_BYTES])
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{
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uint8_t i;
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for (i = 0; i != LED_BYTES; i++) {
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while (!(UCSR0A & (1 << UDRE0)));
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UDR0 = pgm_read_byte(p+i);
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}
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_delay_us(4); /* 16 bits at 4 MHz */
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SET(LED_LCLK);
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CLR(LED_LCLK);
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}
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void led_off(void)
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{
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static uint8_t zero[LED_BYTES] PROGMEM = { 0, };
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led_show_pgm(zero);
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}
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void led_init(void)
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{
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CLR(LED_SCLK);
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OUT(LED_SCLK);
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CLR(LED_LCLK);
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OUT(LED_LCLK);
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UBRR0 = 0; /* maximum data rate */
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UCSR0C =
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1 << UMSEL01 | /* Master SPI */
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1 << UMSEL00 |
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1 << UDORD0 | /* MSB first */
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0 << UCPHA0 | /* SPI Mode 0 */
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0 << UCPOL0;
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UCSR0B =
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1 << TXEN0; /* enable transmitter */
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UBRR0 = 0; /* the manual sez we need this */
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led_off();
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}
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