demo: DAC I2C access (untested)

demo/boards/spec/rtl/system.v

@@ -31,6 +31,8 @@ module system(
 	input btn,
 	output [3:0] led,
 	inout onewire,
+	output scl,
+	inout sda,
 	
 	// TDC
 	output test_clk_oe_n,
@@ -436,10 +438,13 @@ uart #(
 // System Controller
 //---------------------------------------------------------------------------
 wire onewire_drivelow;
+wire gpio_sdc;
+wire gpio_sdaoe;
+wire gpio_sdaout;
 sysctl #(
 	.csr_addr(4'h1),
-	.ninputs(2),
-	.noutputs(5),
+	.ninputs(3),
+	.noutputs(8),
 	.systemid(32'h53504543) /* SPEC */
 ) sysctl (
 	.sys_clk(sys_clk),
@@ -454,12 +459,14 @@ sysctl #(
 	.csr_di(csr_dw),
 	.csr_do(csr_dr_sysctl),
 
-	.gpio_inputs({onewire, btn}),
-	.gpio_outputs({onewire_drivelow, led}),
+	.gpio_inputs({sda, onewire, btn}),
+	.gpio_outputs({gpio_sdaout, gpio_sdaoe, gpio_sdc, onewire_drivelow, led}),
 
 	.hard_reset(hard_reset)
 );
 assign onewire = onewire_drivelow ? 1'b0 : 1'bz;
+assign sdc = ~gpio_sdc ? 1'b0 : 1'bz;
+assign sda = (gpio_sdaoe & ~gpio_sdaout) ? 1'b0 : 1'bz;
 
 //---------------------------------------------------------------------------
 // TDC

demo/boards/spec/synthesis/common.ucf

@@ -20,6 +20,8 @@ NET "led[1]" LOC = F20 | IOSTANDARD = "LVCMOS18";
 NET "led[2]" LOC = F18 | IOSTANDARD = "LVCMOS18";
 NET "led[3]" LOC = C20 | IOSTANDARD = "LVCMOS18";
 NET "onewire" LOC = D4 | IOSTANDARD = "LVCMOS25";
+NET "scl" LOC = F7 | IOSTANDARD = "LVCMOS25";
+NET "sda" LOC = F8 | IOSTANDARD = "LVCMOS25";
 
 # ==== TDC ====
 NET "test_clk_oe_n" LOC = V17 | IOSTANDARD = "LVCMOS25";

demo/software/demo/Makefile

 MMDIR=../..
 include $(MMDIR)/software/include.mak
 
-OBJECTS=crt0.o main.o tdc.o temperature.o
+OBJECTS=crt0.o main.o tdc.o udelay.o temperature.o dac.o
 SEGMENTS=-j .text -j .data -j .rodata
 
 all: demo.bin demo.h0 demo.h1 demo.h2 demo.h3

demo/software/demo/dac.c

+/*
+ * DAC5578 bit-banging driver
+ * Copyright (C) 2007, 2008, 2009, 2010 Sebastien Bourdeauducq
+ *
+ * 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, version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* WARNING/FIXME: The I2C functions clear the other GPIO bits! */
+
+#include <stdio.h>
+
+#include <hw/sysctl.h>
+#include <hw/gpio.h>
+
+#include "udelay.h"
+
+static int i2c_started;
+
+static int i2c_init()
+{
+	unsigned int timeout;
+
+	i2c_started = 0;
+	CSR_GPIO_OUT = GPIO_I2C_SDC;
+	/* Check the I2C bus is ready */
+	timeout = 2000;
+	while((timeout > 0) && (!(CSR_GPIO_IN & GPIO_I2C_SDAIN))) timeout--;
+
+	return timeout;
+}
+
+static void i2c_delay()
+{
+	udelay(20);
+}
+
+/* I2C bit-banging functions from http://en.wikipedia.org/wiki/I2c */
+static unsigned int i2c_read_bit()
+{
+	unsigned int bit;
+
+	/* Let the slave drive data */
+	CSR_GPIO_OUT = 0;
+	i2c_delay();
+	CSR_GPIO_OUT = GPIO_I2C_SDC;
+	i2c_delay();
+	bit = CSR_GPIO_IN & GPIO_I2C_SDAIN;
+	i2c_delay();
+	CSR_GPIO_OUT = 0;
+	return bit;
+}
+
+static void i2c_write_bit(unsigned int bit)
+{
+	if(bit) {
+		CSR_GPIO_OUT = GPIO_I2C_SDAOE|GPIO_I2C_SDAOUT;
+	} else {
+		CSR_GPIO_OUT = GPIO_I2C_SDAOE;
+	}
+	i2c_delay();
+	/* Clock stretching */
+	CSR_GPIO_OUT |= GPIO_I2C_SDC;
+	i2c_delay();
+	CSR_GPIO_OUT &= ~GPIO_I2C_SDC;
+}
+
+static void i2c_start_cond()
+{
+	if(i2c_started) {
+		/* set SDA to 1 */
+		CSR_GPIO_OUT = GPIO_I2C_SDAOE|GPIO_I2C_SDAOUT;
+		i2c_delay();
+		CSR_GPIO_OUT |= GPIO_I2C_SDC;
+	}
+	/* SCL is high, set SDA from 1 to 0 */
+	CSR_GPIO_OUT = GPIO_I2C_SDAOE|GPIO_I2C_SDC;
+	i2c_delay();
+	CSR_GPIO_OUT = GPIO_I2C_SDAOE;
+	i2c_started = 1;
+}
+
+static void i2c_stop_cond()
+{
+	/* set SDA to 0 */
+	CSR_GPIO_OUT = GPIO_I2C_SDAOE;
+	i2c_delay();
+	/* Clock stretching */
+	CSR_GPIO_OUT = GPIO_I2C_SDAOE|GPIO_I2C_SDC;
+	/* SCL is high, set SDA from 0 to 1 */
+	CSR_GPIO_OUT = GPIO_I2C_SDC;
+	i2c_delay();
+	i2c_started = 0;
+}
+
+static unsigned int i2c_write(unsigned char byte)
+{
+	unsigned int bit;
+	unsigned int ack;
+
+	for(bit = 0; bit < 8; bit++) {
+		i2c_write_bit(byte & 0x80);
+		byte <<= 1;
+	}
+	ack = !i2c_read_bit();
+	return ack;
+}
+
+static unsigned char i2c_read(int ack)
+{
+	unsigned char byte = 0;
+	unsigned int bit;
+
+	for(bit = 0; bit < 8; bit++) {
+		byte <<= 1;
+		byte |= i2c_read_bit();
+	}
+	i2c_write_bit(!ack);
+	return byte;
+}
+
+void set_dac_level(int level)
+{
+	if(!i2c_init()) {
+		printf("I2C init failed\n");
+		return;
+	}
+	i2c_start_cond();
+	if(!i2c_write(0x50))
+		printf("DAC not detected\n");
+	i2c_write(0x2f);
+	i2c_write((level & 0xff0) >> 4);
+	i2c_write((level & 0x00f) << 4);
+	i2c_stop_cond();
+}

demo/software/demo/dac.h

+#ifndef __DAC_H
+#define __DAC_H
+
+void set_dac_level(int level);
+
+#endif /* __DAC_H */

demo/software/demo/main.c

@@ -27,6 +27,7 @@
 #include <hw/uart.h>
 
 #include "tdc.h"
+#include "dac.h"
 #include "temperature.h"
 
 /* General address space functions */
@@ -189,6 +190,24 @@ static void crc(char *startaddr, char *len)
 	printf("CRC32: %08x\n", crc32((unsigned char *)addr, length));
 }
 
+static void daclevel(char *level)
+{
+	char *c;
+	unsigned int level2;
+
+	if(*level == 0) {
+		printf("daclevel <level> \n");
+		return;
+	}
+	level2 = strtoul(level, &c, 0);
+	if(*c != 0) {
+		printf("incorrect level\n");
+		return;
+	}
+	set_dac_level(level2);
+}
+
+
 /* Init + command line */
 
 static char *get_token(char **str)
@@ -220,10 +239,11 @@ static void do_command(char *c)
 	else if(strcmp(token, "reboot") == 0) reboot();
 	
 	/* payload */
+	else if(strcmp(token, "temp") == 0) temp();
 	else if(strcmp(token, "rofreq") == 0) rofreq();
 	else if(strcmp(token, "calinfo") == 0) calinfo();
+	else if(strcmp(token, "daclevel") == 0) daclevel(get_token(&c));
 	else if(strcmp(token, "mraw") == 0) mraw();
-	else if(strcmp(token, "temp") == 0) temp();
 	else if(strcmp(token, "diff") == 0) diff();
 	
 	else if(strcmp(token, "") != 0)

demo/software/demo/temperature.c

@@ -20,19 +20,9 @@
 #include <hw/sysctl.h>
 #include <hw/gpio.h>
 
+#include "udelay.h"
 #include "temperature.h"
 
-static void udelay(int usec)
-{
-    int limit;
-    
-    limit = usec*125;
-    CSR_TIMER0_CONTROL = 0;
-    CSR_TIMER0_COUNTER = 0;
-    CSR_TIMER0_CONTROL = TIMER_ENABLE;
-    while(CSR_TIMER0_COUNTER < limit);
-}
-
 static int reset_1w()
 {
     int ok;

demo/software/demo/udelay.c

+#include <hw/sysctl.h>
+
+#include "udelay.h"
+
+void udelay(int usec)
+{
+    int limit;
+    
+    limit = usec*125;
+    CSR_TIMER0_CONTROL = 0;
+    CSR_TIMER0_COUNTER = 0;
+    CSR_TIMER0_CONTROL = TIMER_ENABLE;
+    while(CSR_TIMER0_COUNTER < limit);
+}

demo/software/demo/udelay.h

+#ifndef __UDELAY_H
+#define __UDELAY_H
+
+void udelay(int usec);
+
+#endif /* __UDELAY_H */

demo/software/include/hw/gpio.h

@@ -22,6 +22,7 @@
 /* Inputs */
 #define GPIO_PB2		(0x00000001)
 #define GPIO_1W			(0x00000002)
+#define GPIO_I2C_SDAIN		(0x00000004)
 
 /* Outputs */
 #define GPIO_LD2		(0x00000001)
@@ -29,5 +30,8 @@
 #define GPIO_LD4		(0x00000004)
 #define GPIO_LD5		(0x00000008)
 #define GPIO_1W_DRIVELOW	(0x00000010)
+#define GPIO_I2C_SDC		(0x00000020)
+#define GPIO_I2C_SDAOE		(0x00000040)
+#define GPIO_I2C_SDAOUT		(0x00000080)
 
 #endif /* __HW_GPIO_H */