From 57b81079eedef34913838e6a2d8980db03fc1393 Mon Sep 17 00:00:00 2001
From: Matthias Merz <matthias@merz-ka.de>
Date: Fri, 10 Dec 2010 22:05:28 +0100
Subject: [PATCH] symlink spi-routines to slave

---
 firmware/slavechip/spi.c | 78 ++++++++++++++++++++++++++++++++++++++++
 firmware/slavechip/spi.h |  6 ++++
 2 files changed, 84 insertions(+)
 create mode 100644 firmware/slavechip/spi.c
 create mode 100644 firmware/slavechip/spi.h

diff --git a/firmware/slavechip/spi.c b/firmware/slavechip/spi.c
new file mode 100644
index 0000000..870a16d
--- /dev/null
+++ b/firmware/slavechip/spi.c
@@ -0,0 +1,78 @@
+#include <avr/io.h>
+#include <stdint.h>
+#include <math.h>
+
+
+#include <spi.h>
+
+
+/* SPI framework.
+ *
+ * currently alpha, uses interrupts, single master/single slave operation
+ */
+
+
+uint8_t * volatile spi_writeptr;
+uint8_t * volatile spi_readptr;
+uint8_t volatile spi_writelen;
+uint8_t volatile spi_readlen;
+uint8_t spi_readbuf[SPI_READBUF_LEN];
+
+
+void spi_init(){
+	uint8_t spcr, spsr, d;
+
+	/* calculate clock divisor,
+	 * gcc with optimize will do that calculation compile-time. */
+	uint8_t spi_clock_divisor(){
+		double d; 
+		d = F_CPU / SPI_BAUDRATE;
+		d = ceil((log(d)/log(2))*0.95); // clock needs dividing by 2^d
+										// the 0.95 to avoid ceil issues
+		return d-1;  // the -1 because minimum divisor is /2
+	}
+
+	d = spi_clock_divisor();
+	if(d>7){
+                #warning "spi baudrate too slow, cannot be set"
+		d=7;
+	}
+
+	//TODO: DDRs setzen
+	spsr = 0;
+	spsr |=	(d & 1) ? 0 : _BV(SPI2X);
+	spcr = 0 | _BV(SPIE) | _BV(SPE);
+	spcr |= (d & 2) ? _BV(SPR0) : 0;
+	spcr |= (d & 4) ? _BV(SPR1) : 0;
+
+#ifdef SPI_MASTER
+	spcr |= _BV(MSTR);
+#endif		
+	SPCR = spcr;
+	SPSR = spsr;
+
+	// initialize interface for ISR:
+	spi_readptr = spi_readbuf;
+	spi_readlen = SPI_READBUF_LEN;
+	spi_writeptr = NULL;
+}
+
+// return true on success, false on error
+uint8_t spi_write(uint8_t *data, uint8_t len){
+	if(spi_writeptr != NULL){
+		return 0
+	}
+	spi_writeptr = data;
+	spi_writelen = len;
+	//TODO: handle SS, write out first byte
+	return 1;
+}
+
+#ifdef SPI_MASTER
+ISR(SPI_vector){
+
+
+
+
+}
+#endif //SPI_MASTER
diff --git a/firmware/slavechip/spi.h b/firmware/slavechip/spi.h
new file mode 100644
index 0000000..bc9969b
--- /dev/null
+++ b/firmware/slavechip/spi.h
@@ -0,0 +1,6 @@
+#define SPI_BAUDRATE 1000000
+#define SPI_MASTER 1
+#define SPI_READBUF_LEN 32
+
+uint8_t spi_write(uint8_t *data, uint8_t len);
+void spi_init();