kopia lustrzana https://github.com/bristol-seds/pico-tracker
105 wiersze
3.0 KiB
C
105 wiersze
3.0 KiB
C
/*
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* SPI bit-banging! Yay
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* Copyright (C) 2014 Richard Meadows <richardeoin>
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include "samd20.h"
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#include "system/port.h"
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/** Should be at least 20ns or something. Why am I bit-banging this? */
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#define BIT_DELAY __NOP
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#define BIT_TOGGLE(bit) do { \
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PORTA.OUTTGL.reg = bit; } while (0)
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#define BIT_SET(bit) do { \
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PORTA.OUTSET.reg = bit; } while (0)
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#define BIT_CLEAR(bit) do { \
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PORTA.OUTCLR.reg = bit; } while (0)
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#define BIT_READ(bit) (PORTA.IN.reg & bit)
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uint32_t mosi_mask = 0;
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uint32_t miso_mask = 0;
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uint32_t sck_mask = 0;
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void spi_bitbang_init(const uint8_t mosi,
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const uint8_t miso,
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const uint8_t sck)
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{
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/* Set the masks */
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mosi_mask = (1 << mosi);
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miso_mask = (1 << miso);
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sck_mask = (1 << sck);
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/* Configure the output pins */
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if (mosi == miso) { /* Loopback */
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port_pin_set_config(mosi,
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PORT_PIN_DIR_OUTPUT_WTH_READBACK,/* Direction */
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PORT_PIN_PULL_NONE, /* Pull */
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false); /* Powersave */
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} else { /* No loopback */
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port_pin_set_config(mosi,
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PORT_PIN_DIR_OUTPUT, /* Direction */
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PORT_PIN_PULL_NONE, /* Pull */
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false); /* Powersave */
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port_pin_set_config(miso,
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PORT_PIN_DIR_INPUT, /* Direction */
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PORT_PIN_PULL_UP, /* Pull */
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false); /* Powersave */
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}
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port_pin_set_config(sck,
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PORT_PIN_DIR_OUTPUT, /* Direction */
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PORT_PIN_PULL_NONE, /* Pull */
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false); /* Powersave */
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/* Set output pins to default values */
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BIT_SET(mosi_mask);
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BIT_CLEAR(sck_mask);
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}
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uint8_t spi_bitbang_transfer(uint8_t byte)
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{
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for (uint8_t counter = 0; counter < 8; counter++) {
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/* Set output data */
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if (byte & 0x80) {
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BIT_SET(mosi_mask);
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} else {
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BIT_CLEAR(mosi_mask);
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}
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byte <<= 1;
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BIT_DELAY();
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/* Latch Data into Slave */
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BIT_TOGGLE(sck_mask);
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BIT_DELAY();
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/* Read Data */
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if (BIT_READ(miso_mask)) {
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byte |= 0x1;
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}
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/* Slave shifts out next data bit */
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BIT_TOGGLE(sck_mask);
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}
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return byte;
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}
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