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/* mbed Microcontroller Library
* Copyright (c) 2006-2013 ARM Limited
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "spi_api.h"
#include <math.h>
#include "cmsis.h"
#include "pinmap.h"
#include "clk_freqs.h"
#include "PeripheralPins.h"
void spi_init(spi_t *obj, PinName mosi, PinName miso, PinName sclk, PinName ssel) {
// determine the SPI to use
SPIName spi_mosi = (SPIName)pinmap_peripheral(mosi, PinMap_SPI_MOSI);
SPIName spi_miso = (SPIName)pinmap_peripheral(miso, PinMap_SPI_MISO);
SPIName spi_sclk = (SPIName)pinmap_peripheral(sclk, PinMap_SPI_SCLK);
SPIName spi_ssel = (SPIName)pinmap_peripheral(ssel, PinMap_SPI_SSEL);
SPIName spi_data = (SPIName)pinmap_merge(spi_mosi, spi_miso);
SPIName spi_cntl = (SPIName)pinmap_merge(spi_sclk, spi_ssel);
obj->spi = (SPI_Type*)pinmap_merge(spi_data, spi_cntl);
MBED_ASSERT((int)obj->spi != NC);
// enable power and clocking
switch ((int)obj->spi) {
case SPI_0: SIM->SCGC5 |= 1 << 11; SIM->SCGC4 |= 1 << 22; break;
case SPI_1: SIM->SCGC5 |= 1 << 13; SIM->SCGC4 |= 1 << 23; break;
}
// set default format and frequency
if (ssel == NC) {
spi_format(obj, 8, 0, 0); // 8 bits, mode 0, master
} else {
spi_format(obj, 8, 0, 1); // 8 bits, mode 0, slave
}
spi_frequency(obj, 1000000);
// enable SPI
obj->spi->C1 |= SPI_C1_SPE_MASK;
// pin out the spi pins
pinmap_pinout(mosi, PinMap_SPI_MOSI);
pinmap_pinout(miso, PinMap_SPI_MISO);
pinmap_pinout(sclk, PinMap_SPI_SCLK);
if (ssel != NC) {
pinmap_pinout(ssel, PinMap_SPI_SSEL);
}
}
void spi_free(spi_t *obj) {
// [TODO]
}
void spi_format(spi_t *obj, int bits, int mode, int slave) {
MBED_ASSERT(bits == 8);
MBED_ASSERT((mode >= 0) && (mode <= 3));
uint8_t polarity = (mode & 0x2) ? 1 : 0;
uint8_t phase = (mode & 0x1) ? 1 : 0;
uint8_t c1_data = ((!slave) << 4) | (polarity << 3) | (phase << 2);
// clear MSTR, CPOL and CPHA bits
obj->spi->C1 &= ~(0x7 << 2);
// write new value
obj->spi->C1 |= c1_data;
}
void spi_frequency(spi_t *obj, int hz) {
uint32_t error = 0;
uint32_t p_error = 0xffffffff;
uint32_t ref = 0;
uint8_t spr = 0;
uint8_t ref_spr = 0;
uint8_t ref_prescaler = 0;
// bus clk
uint32_t PCLK = bus_frequency();
uint8_t prescaler = 1;
uint8_t divisor = 2;
for (prescaler = 1; prescaler <= 8; prescaler++) {
divisor = 2;
for (spr = 0; spr <= 8; spr++, divisor *= 2) {
ref = PCLK / (prescaler*divisor);
if (ref > (uint32_t)hz)
continue;
error = hz - ref;
if (error < p_error) {
ref_spr = spr;
ref_prescaler = prescaler - 1;
p_error = error;
}
}
}
// set SPPR and SPR
obj->spi->BR = ((ref_prescaler & 0x7) << 4) | (ref_spr & 0xf);
}
static inline int spi_writeable(spi_t * obj) {
return (obj->spi->S & SPI_S_SPTEF_MASK) ? 1 : 0;
}
static inline int spi_readable(spi_t * obj) {
return (obj->spi->S & SPI_S_SPRF_MASK) ? 1 : 0;
}
int spi_master_write(spi_t *obj, int value) {
// wait tx buffer empty
while(!spi_writeable(obj));
obj->spi->D = (value & 0xff);
// wait rx buffer full
while (!spi_readable(obj));
return obj->spi->D & 0xff;
}
int spi_slave_receive(spi_t *obj) {
return spi_readable(obj);
}
int spi_slave_read(spi_t *obj) {
return obj->spi->D;
}
void spi_slave_write(spi_t *obj, int value) {
while (!spi_writeable(obj));
obj->spi->D = value;
}
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