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