spiio/: simple SPI I/O example

spiio/Makefile

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+CC=mipsel-openwrt-linux-uclibc-gcc
+
+CFLAGS=-Wall -g
+
+.PHONY:		all clean spotless
+
+all:		spiio
+
+clean:
+		rm -f spiio
+
+spotless:	clean

spiio/spiio.c

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+/*
+ * spiio.c - Very simple SPI I/O example
+ *
+ * Written 2011 by Werner Almesberger
+ * Copyright 2011 Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+
+
+enum {
+	VDD_OFF		= 1 << 2,	/* VDD disable, PD02 */
+	MMC_CMD		= 1 << 8,	/* CMD, PD08 */
+	MMC_CLK		= 1 << 9,	/* CLK, PD09 */
+	MMC_DAT0	= 1 << 10,	/* DAT0, PD10 */
+	MMC_DAT1	= 1 << 11,	/* DAT1, PD11 */
+	MMC_DAT2	= 1 << 12,	/* DAT2, PD12 */
+	MMC_DAT3	= 1 << 13,	/* DAT3/CD, PD13 */
+};
+
+#define	MOSI	MMC_CMD
+#define	MISO	MMC_DAT0
+#define	SCLK	MMC_DAT2
+#define	nSEL	MMC_DAT3
+
+
+#define SOC_BASE	0x10000000
+
+#define	REG(n)	(*(volatile uint32_t *) (mem+(n)))
+
+#define GPIO(n)	REG(0x10000+(n))
+
+#define	PDPIN	GPIO(0x300)	/* port D pin level */
+#define PDDATS	GPIO(0x314)	/* port D data set */
+#define PDDATC	GPIO(0x318)	/* port D data clear */
+#define PDFUNS	GPIO(0x344)	/* port D function set */
+#define PDFUNC	GPIO(0x348)	/* port D function clear */
+#define PDDIRS	GPIO(0x364)	/* port D direction set */
+#define PDDIRC	GPIO(0x368)	/* port D direction clear */
+
+#define	PAGE_SIZE	4096
+
+
+static void *mem;
+
+
+/* ----- Low-level SPI operations ------------------------------------------ */
+
+
+static void spi_begin(void)
+{
+	PDDATC = nSEL;
+}
+
+
+static void spi_end(void)
+{
+	PDDATS = nSEL;
+}
+
+
+static void spi_send(uint8_t v)
+{
+	uint8_t mask;
+
+	for (mask = 0x80; mask; mask >>= 1) {
+		if (v & mask)
+			PDDATS = MOSI;
+		else
+			PDDATC = MOSI;
+		PDDATS = SCLK;
+		PDDATC = SCLK;
+	}
+}
+
+
+static uint8_t spi_recv(void)
+{
+	uint8_t res = 0;
+        uint8_t mask;
+
+	for (mask = 0x80; mask; mask >>= 1) {
+		if (PDPIN & MISO)
+			res |= mask;
+		PDDATS = SCLK;
+		PDDATC = SCLK;
+	}
+        return res;
+}
+
+
+static uint8_t spi_bidir(uint8_t v)
+{
+	uint8_t res = 0;
+	uint8_t mask;
+
+	for (mask = 0x80; mask; mask >>= 1) {
+		if (PDPIN & MISO)
+			res |= mask;
+		if (v & mask)
+			PDDATS = MOSI;
+		else
+			PDDATC = MOSI;
+		PDDATS = SCLK;
+		PDDATC = SCLK;
+	}
+        return res;
+}
+
+
+/* ----  High-level -------------------------------------------------------- */
+
+
+static void spi_io(const char *s)
+{
+	const char *p;
+	uint8_t ch;
+
+	spi_begin();
+	for (p = s; *p; p++) {
+		ch = spi_bidir(*s);
+		if (!ch)
+			continue;
+		if (strchr("\t\n\r", ch) || (ch >= ' ' && ch <= '~'))
+			putchar(ch);
+		else
+			putchar('?');
+	}
+	spi_end();
+	putchar('\n');
+}
+
+
+int main(int argc, char **argv)
+{
+	int fd, i;
+
+	fd = open("/dev/mem", O_RDWR | O_SYNC);
+	if (fd < 0) {
+		perror("/dev/mem");
+		exit(1);
+	}
+	mem = mmap(NULL, PAGE_SIZE*3*16, PROT_READ | PROT_WRITE,
+	    MAP_SHARED, fd, SOC_BASE);
+        if (mem == MAP_FAILED) {
+                perror("mmap");
+                exit(1);
+        }
+
+	/* set the output levels */
+	PDDATS = nSEL | VDD_OFF;
+	PDDATC = SCLK;
+
+	PDFUNC = MOSI | MISO | SCLK | nSEL;
+
+	/* set the pin directions */
+	PDDIRC = MISO;
+	PDDIRS = MOSI | SCLK | nSEL;
+
+	for (i = 1; i != argc; i++)
+		spi_io(argv[i]);
+
+	/* make all MMC pins inputs */
+	PDDIRC = MOSI | MISO | SCLK | nSEL;
+
+	return 0;
+}