143 lines
4.0 KiB
C
143 lines
4.0 KiB
C
#ifndef _SPI_H
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#define _SPI_H
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#include "config_wrapper.h"
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#include "arduino.h"
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#include "pinio.h"
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#ifdef SPI
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/**
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Test configuration.
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*/
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#ifdef __ARM_LPC1114__
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#error SPI (SD_CARD_SELECT_PIN, TEMP_MAX6675, TEMP_MCP3008) not yet supported on LPC1114.
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#endif
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// Uncomment this to double SPI frequency from (F_CPU / 4) to (F_CPU / 2).
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//#define SPI_2X
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/** Initialise SPI subsystem.
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*/
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void spi_init(void);
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/** SPI device selection.
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Because out famous WRITE() macro works with constant pins, only, we define
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a (de)select function for each of them. In case you add another SPI device,
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you also have to define a pair of these functions.
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*/
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#ifdef SD
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static void spi_select_sd(void) __attribute__ ((always_inline));
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inline void spi_select_sd(void) {
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WRITE(SD_CARD_SELECT_PIN, 0);
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}
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static void spi_deselect_sd(void) __attribute__ ((always_inline));
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inline void spi_deselect_sd(void) {
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WRITE(SD_CARD_SELECT_PIN, 1);
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}
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#endif /* SD */
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#ifdef TEMP_MAX6675
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// Note: the pin choosen with DEFINE_TEMP_SENSOR() in the board configuration
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// should be used here. Currently it's a requirement that this device's
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// Chip Select pin is actually SS, while any other pin would work just
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// as fine.
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static void spi_select_max6675(void) __attribute__ ((always_inline));
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inline void spi_select_max6675(void) {
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WRITE(SS, 0);
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}
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static void spi_deselect_max6675(void) __attribute__ ((always_inline));
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inline void spi_deselect_max6675(void) {
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WRITE(SS, 1);
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}
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#endif /* TEMP_MAX6675 */
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#ifdef TEMP_MCP3008
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static void spi_select_mcp3008(void) __attribute__ ((always_inline));
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inline void spi_select_mcp3008(void) {
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WRITE(MCP3008_SELECT_PIN, 0);
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}
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static void spi_deselect_mcp3008(void) __attribute__ ((always_inline));
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inline void spi_deselect_mcp3008(void) {
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WRITE(MCP3008_SELECT_PIN, 1);
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}
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#endif /* TEMP_MCP3008 */
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#ifdef __AVR__
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/** Set SPI clock speed to something between 100 and 400 kHz.
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This is needed for initialising SD cards. We set the whole SPCR register
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in one step, because this is faster than and'ing in bits.
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About dividers. We have:
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SPCR = 0x50; // normal mode: (F_CPU / 4), 2x mode: (F_CPU / 2)
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SPCR = 0x51; // normal mode: (F_CPU / 16), 2x mode: (F_CPU / 8)
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SPCR = 0x52; // normal mode: (F_CPU / 64), 2x mode: (F_CPU / 32)
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SPCR = 0x53; // normal mode: (F_CPU / 128), 2x mode: (F_CPU / 64)
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For now we always choose the /128 divider, because it fits nicely in all
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expected situations:
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F_CPU 16 MHz 20 MHz
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SPI clock normal mode 125 kHz 156 kHz
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SPI clock 2x mode 250 kHz 312 kHz
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About the other bits:
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0x50 = (1 << SPE) | (1 << MSTR);
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This is Master SPI mode, SPI enabled, interrupts disabled, polarity mode 0
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(right for SD cards).
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See ATmega164/324/644/1284 data sheet, section 18.5.1, page 164.
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*/
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static void spi_speed_100_400(void) __attribute__ ((always_inline));
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inline void spi_speed_100_400(void) {
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SPCR = 0x53;
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}
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/** Set SPI clock speed to maximum.
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*/
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static void spi_speed_max(void) __attribute__ ((always_inline));
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inline void spi_speed_max(void) {
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SPCR = 0x50; // See list at spi_speed_100_400().
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}
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/** Exchange a byte over SPI.
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Yes, SPI is that simple and you can always only swap bytes. To retrieve
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a byte, simply send a dummy value, like: mybyte = spi_rw(0);
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As we operate in master mode, we don't have to fear to hang due to
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communications errors (e.g. missing a clock beat).
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Note: insisting on inlinig (attribute always_inline) costs about 80 bytes
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with the current SD card code.
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*/
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static uint8_t spi_rw(uint8_t) __attribute__ ((always_inline));
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inline uint8_t spi_rw(uint8_t byte) {
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SPDR = byte;
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loop_until_bit_is_set(SPSR, SPIF);
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return SPDR;
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}
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#elif defined __ARM_STM32F411__
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void spi_speed_100_400(void);
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void spi_speed_max(void);
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static uint8_t spi_rw(uint8_t) __attribute__ ((always_inline));
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inline uint8_t spi_rw(uint8_t byte) {
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SPI2->DR = byte;
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while(!(SPI2->SR & SPI_SR_TXE));
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while(!(SPI2->SR & SPI_SR_RXNE));
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while(SPI2->SR & SPI_SR_BSY);
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return SPI2->DR;
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}
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#endif /* AVR / STM32F411 */
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#endif /* SPI */
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#endif /* _SPI_H */
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