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add support for SPI with hardware USI on ATtiny devices #11

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add support for SPI with hardware USI on ATtiny devices #11

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9 changes: 7 additions & 2 deletions src/mcp2515_private.h
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Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,6 @@
#include "utils.h"

#include "can_private.h"
#include "spi.h"

// ----------------------------------------------------------------------------

Expand Down Expand Up @@ -81,14 +80,20 @@
#define P_MOSI B,0
#define P_MISO B,1
#define P_SCK B,2

#define USE_SOFTWARE_SPI 1
#define SUPPORT_FOR_MCP2515__
#elif defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__)
#define P_MOSI A,5
#define P_MISO A,6
#define P_SCK A,4
#define SUPPORT_FOR_MCP2515__
#else
#error choosen AVR-type is not supported yet!
#endif
#endif

#include "spi.h"


#ifdef SUPPORT_FOR_MCP2515__

Expand Down
32 changes: 2 additions & 30 deletions src/mcp2515_write_id.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,35 +30,7 @@

#include "mcp2515_private.h"
#ifdef SUPPORT_FOR_MCP2515__

// ----------------------------------------------------------------------------
#ifdef USE_SOFTWARE_SPI

static uint8_t usi_interface_spi_temp;

static void spi_start(uint8_t data) {
usi_interface_spi_temp = spi_putc(data);
}

static uint8_t spi_wait(void) {
return usi_interface_spi_temp;
}

#else

static void spi_start(uint8_t data) {
SPDR = data;
}

static uint8_t spi_wait(void) {
// warten bis der vorherige Werte geschrieben wurde
while(!(SPSR & (1<<SPIF)))
;

return SPDR;
}

#endif
#include "spi.h"

// ----------------------------------------------------------------------------
/* Schreibt eine CAN ID in die Register des MCP2515
Expand Down Expand Up @@ -124,7 +96,7 @@ void mcp2515_write_id(const uint32_t *id, uint8_t extended)
}
}

#else
#else // USE_EXTENDED_CANID

void mcp2515_write_id(const uint16_t *id)
{
Expand Down
21 changes: 13 additions & 8 deletions src/spi.c
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Original file line number Diff line number Diff line change
Expand Up @@ -60,19 +60,28 @@
#error SPI_PRESCALER not defined!
#endif

#ifdef USE_SOFTWARE_SPI
uint8_t usi_interface_spi_temp;
#endif


// ----------------------------------------------------------------------------
void mcp2515_spi_init(void)
{
#ifndef USE_SOFTWARE_SPI
// Aktivieren des SPI Master Interfaces
#if defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__)
USICR = (1<<USIWM0)|(1<<USICS1)|(1<<USICLK)|(1<<USITC);
#else
SPCR = (1<<SPE)|(1<<MSTR) | R_SPCR;
SPSR = R_SPSR;
#endif
#endif
#endif /* !USE_SOFTWARE_SPI */
}

// ----------------------------------------------------------------------------
// Schreibt/liest ein Byte ueber den Hardware SPI Bus
// \return gelesene Daten

uint8_t spi_putc(uint8_t data)
{
Expand Down Expand Up @@ -107,13 +116,9 @@ uint8_t spi_putc(uint8_t data)
#else

// put byte in send-buffer
SPDR = data;

// wait until byte was send
while( !( SPSR & (1<<SPIF) ) )
;

return SPDR;
spi_start(data);
// wait until byte was send
return spi_wait();

#endif
}
Expand Down
23 changes: 21 additions & 2 deletions src/spi.h
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Original file line number Diff line number Diff line change
Expand Up @@ -59,7 +59,7 @@ extern uint8_t spi_putc(uint8_t data);
// ----------------------------------------------------------------------------
#ifdef USE_SOFTWARE_SPI

static uint8_t usi_interface_spi_temp;
extern uint8_t usi_interface_spi_temp;

extern __attribute__ ((gnu_inline)) inline void spi_start(uint8_t data) {
usi_interface_spi_temp = spi_putc(data);
Expand All @@ -71,18 +71,37 @@ extern __attribute__ ((gnu_inline)) inline uint8_t spi_wait(void) {

#else

/** Initiate SPI write transfer
* \param data The data to transfer
*/
extern __attribute__ ((gnu_inline)) inline void spi_start(uint8_t data) {
#if defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__)
USIDR = data; // Daten in Data Register laden
USISR |= (1<<USIOIF); // Überlaufflag löschen
#else
SPDR = data;
#endif
}

/** Wait for SPI to complete operation (all data transferred)
* \return data received from SPI
*/
extern __attribute__ ((gnu_inline)) inline uint8_t spi_wait(void) {
// warten bis der vorherige Werte geschrieben wurde
#if defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__)
while(!(USISR & (1<<USIOIF))) {
USICR |= (1<<USITC); // toggle clk
}

return USIDR;
#else
while(!(SPSR & (1<<SPIF)))
;

return SPDR;
#endif
}

#endif
#endif // !USE_SOFTWARE_SPI

#endif // SPI_H