From 4ebf0dc69153c1f715f934a7abce4fdefbc4453f Mon Sep 17 00:00:00 2001
From: Lars-Dominik Braun <lars@6xq.net>
Date: Thu, 30 Jan 2014 14:31:34 +0100
Subject: Initial import

---
 main.c | 359 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 359 insertions(+)
 create mode 100644 main.c

(limited to 'main.c')

diff --git a/main.c b/main.c
new file mode 100644
index 0000000..e5a1056
--- /dev/null
+++ b/main.c
@@ -0,0 +1,359 @@
+/* cpu freq */
+#define F_CPU 1000000
+
+#include <avr/io.h>
+#include <util/delay.h>
+#include <stdio.h>
+
+/* cpu runs at 1mhz */
+
+/* i2c device addresses */
+#define L2GD20 0b11010100
+#define L2GD20_WHOAMI 0xf
+#define L2GD20_CTRLREG1 0x20
+#define LIS302DL 0b00111000
+#define LIS302DL_WHOAMI 0xf
+
+/* i2c constants */
+#define TW_READ 1
+#define TW_WRITE 0
+#define TW_STATUS (TWSR & 0xF8)
+
+void twStart () {
+	/* disable stop, reset twint, enable start, enable i2c */
+	TWCR = (TWCR & ~(1 << TWSTO)) | (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);
+}
+
+void twStop () {
+	/* disable start, reset twint, enable stop, enable i2c */
+	TWCR = (TWCR & ~(1 << TWSTA)) | (1 << TWINT) | (1 << TWSTO) | (1 << TWEN);
+}
+
+void twFlush () {
+	/* disable start/stop, reset twint, enable i2c */
+	TWCR = (TWCR & ~((1 << TWSTA) | (1 << TWSTO))) | (1 << TWINT) | (1 << TWEN);
+}
+
+void twWait () {
+	while (!(TWCR & (1 << TWINT)));
+}
+
+void twInit () {
+	/* set scl to 3.6 kHz (at 1Mhz CPU speed)*/
+	TWBR = 2;
+	TWSR |= 0x3; /* set prescaler to 64 */
+}
+
+void ledInit () {
+	/* set led1,led2 to output */
+	DDRB |= (1 << PB6) | (1 << PB7);
+	/* set led3,led4,led5,led6 to output */
+	DDRD |= (1 << PD2) | (1 << PD3) | (1 << PD4) | (1 << PD5);
+}
+
+/* show data with leds */
+void ledShow (unsigned char val) {
+	PORTB = (PORTB & ~((1 << PB6) | (1 << PB7))) | ((val & 0x3) << PB6);
+	PORTD = (PORTD & ~((1 << PD2) | (1 << PD3) | (1 << PD4) | (1 << PD5))) | (((val >> 2) & 0xf) << PD2);
+}
+
+void uartInit () {
+	/* Set baud rate (9600, double speed, at 1mhz) */
+	UBRR0H = 0;
+	UBRR0L = 12;
+	/* enable double speed mode */
+	UCSR0A = (1 << U2X0);
+	/* Enable receiver and transmitter */
+	UCSR0B = (1<<RXEN0)|(1<<TXEN0);
+	/* Set frame format: 8 data, 1 stop bit, even parity */
+	UCSR0C = (1<<UPM01) | (0 << UPM00) | (0<<USBS0)|(3<<UCSZ00);
+}
+
+/* blocking uart send
+ */
+void uartSend (unsigned char data) {
+	/* Wait for empty transmit buffer */
+	while (!( UCSR0A & (1<<UDRE0)));
+	/* Put data into buffer, sends the data */
+	UDR0 = data;
+}
+
+int uartPutc (char c, FILE *stream) {
+	if (c == '\n') {
+		uartSend ('\r');	
+	}
+	uartSend (c);
+	return 0;
+}
+
+static FILE mystdout = FDEV_SETUP_STREAM (uartPutc, NULL, _FDEV_SETUP_WRITE);
+
+unsigned char uartReceive () {
+	/* Wait for data to be received */
+	while ( !(UCSR0A & (1<<RXC0)) );
+	/* Get and return received data from buffer */
+	return UDR0;
+}
+
+void cpuInit () {
+	/* enter change prescaler mode */
+	CLKPR = CLKPCE << 1;
+	/* write new prescaler = 8 (i.e. 1Mhz clock frequency) */
+	CLKPR = 0b00000011;
+}
+
+#if 0
+void test1 () {
+	while (1) {
+		unsigned char res = uartReceive ();
+		for (unsigned char i = 0; i < 3; i++) {
+			PORTB ^= (1 << PB6);
+			_delay_ms (1000);
+		}
+		/* no frame or parity error? */
+		if (!(UCSR0A & (1 << FE0)) && !(UCSR0A & (1 << UPE0))) {
+			ledShow (res);
+		}
+		uartSend (res);
+		/* check tx complete */
+		while ( !(UCSR0A & (1<<TXC0)) );
+		/* clear tx complete */
+		UCSR0A |= (1<<TXC0);
+	}
+}
+#endif
+
+#if 0
+void enumreg () {
+	printf ("enumerating registers\n");
+	unsigned char reg[] = {0xf, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37};
+	//unsigned char reg[] = {0xf, 0x20, 0x21, 0x22, 0x23, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2d, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f};
+	for (unsigned char i = 0; i < sizeof (reg)/sizeof(*reg); i++) {
+		printf ("start\n");
+		twStart ();
+		twWait ();
+		unsigned char status = 0x0;
+		
+		/* check status code */
+		if ((status = TW_STATUS) == 0x8) {
+			printf ("start ok\nwriting dev address\n");
+			
+			/* write device address and write bit */
+			TWDR = L2GD20 | TW_WRITE;
+			if (TWCR & (1 << TWWC)) {
+				printf("write collision\n");
+			}
+			twFlush ();
+			twWait ();
+			if ((status = TW_STATUS) == 0x18) {
+				printf ("ok\n");
+				} else {
+				printf ("fail with code %x\n", status);
+			}
+
+			printf ("writing subaddress %x\n", reg[i]);
+			
+			/* write subaddress (actually i2c data) */
+			TWDR = reg[i];
+			if (TWCR & (1 << TWWC)) {
+				printf("write collision\n");
+			}
+			twFlush ();
+			twWait ();
+			if ((status = TW_STATUS) == 0x28) {
+				printf ("ok\n");
+				} else {
+				printf ("fail with code %x\n", status);
+			}
+
+			printf ("starting again\n");
+			
+			/* repeated start */
+			twStart ();
+			twWait ();
+			if ((status = TW_STATUS) == 0x10) {
+				printf ("ok\n");
+				} else {
+				printf ("fail with code %x\n", status);
+			}
+			
+			printf ("writing read request\n");
+
+			/* write device address and read bit */
+			TWDR = L2GD20 | TW_READ;
+			if (TWCR & (1 << TWWC)) {
+				printf("write collision\n");
+			}
+			twFlush ();
+			twWait ();
+			if ((status = TW_STATUS) == 0x40) {
+				printf ("ok\n");
+				} else {
+				printf ("fail with code %x\n", status);
+			}
+			
+			/* clear twint and wait for response */
+			twFlush ();
+			twWait ();
+			if ((status = TW_STATUS) == 0x58) {
+				printf ("ok\n");
+				} else {
+				printf ("fail with code %x\n", status);
+			}
+			unsigned char ret = TWDR;
+			
+			printf ("register %x is %x\n", reg[i], ret);
+			
+			twStop ();
+			
+			printf ("done\n");
+			
+			/* there is no way to tell whether stop has been sent or not, just wait */
+			_delay_ms (10);
+			} else {
+			printf ("fail\n");
+		}
+	}
+}
+#endif
+	
+int main(void) {
+	cpuInit ();
+	ledInit ();
+	twInit ();
+	uartInit ();
+	
+	/* redirect stdout */
+	stdout = &mystdout;
+	
+	printf ("initialization done\n");
+
+	/* disable power-down-mode */
+	twStart ();
+	twWait ();
+	unsigned char status = 0x0;
+	
+	/* check status code */
+	if ((status = TW_STATUS) == 0x8) {
+		/* write device address and write bit */
+		TWDR = L2GD20 | TW_WRITE;
+		if (TWCR & (1 << TWWC)) {
+			printf("write collision\n");
+		}
+		twFlush ();
+		twWait ();
+		if ((status = TW_STATUS) == 0x18) {
+		} else {
+			printf ("fail with code %x\n", status);
+		}
+		
+		/* write subaddress (actually i2c data) */
+		TWDR = 0x20;
+		if (TWCR & (1 << TWWC)) {
+			printf("write collision\n");
+		}
+		twFlush ();
+		twWait ();
+		if ((status = TW_STATUS) == 0x28) {
+		} else {
+			printf ("fail with code %x\n", status);
+		}
+					
+		/* write actual data */
+		TWDR = 0b00001111;
+		if (TWCR & (1 << TWWC)) {
+			printf("write collision\n");
+		}
+		twFlush ();
+		twWait ();
+		if ((status = TW_STATUS) == 0x28) {
+		} else {
+			printf ("fail with code %x\n", status);
+		}
+		
+		twStop ();
+		_delay_ms (100);
+	} else {
+		printf ("write: start failed\n");
+	}
+
+	while (1) {
+		unsigned char reg[] = {0x28, 0x29, 0x2a, 0x2b, 0x2d};
+		unsigned char val[6];
+		//unsigned char reg[] = {0xf, 0x20, 0x21, 0x22, 0x23, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2d, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f};
+		for (unsigned char i = 0; i < sizeof (reg)/sizeof(*reg); i++) {
+			twStart ();
+			twWait ();
+			unsigned char status = 0x0;
+		
+			/* check status code */
+			if ((status = TW_STATUS) == 0x8) {
+		
+				/* write device address and write bit */
+				TWDR = L2GD20 | TW_WRITE;
+				if (TWCR & (1 << TWWC)) {
+					printf("write collision\n");
+				}
+				twFlush ();
+				twWait ();
+				if ((status = TW_STATUS) == 0x18) {
+				} else {
+					printf ("fail with code %x\n", status);
+				}
+		
+				/* write subaddress (actually i2c data) */
+				TWDR = reg[i];
+				if (TWCR & (1 << TWWC)) {
+					printf("write collision\n");
+				}
+				twFlush ();
+				twWait ();
+				if ((status = TW_STATUS) == 0x28) {
+				} else {
+					printf ("fail with code %x\n", status);
+				}
+		
+				/* repeated start */
+				twStart ();
+				twWait ();
+				if ((status = TW_STATUS) == 0x10) {
+				} else {
+					printf ("fail with code %x\n", status);
+				}
+			
+				/* write device address and read bit */
+				TWDR = L2GD20 | TW_READ;
+				if (TWCR & (1 << TWWC)) {
+					printf("write collision\n");
+				}
+				twFlush ();
+				twWait ();
+				if ((status = TW_STATUS) == 0x40) {
+				} else {
+					printf ("fail with code %x\n", status);
+				}
+			
+				/* clear twint and wait for response */
+				twFlush ();
+				twWait ();
+				if ((status = TW_STATUS) == 0x58) {
+				} else {
+					printf ("fail with code %x\n", status);
+				}
+				unsigned char ret = TWDR;
+				val[i] = ret;
+			
+				twStop ();
+	
+				/* there is no way to tell whether stop has been sent or not, just wait */
+				_delay_ms (10);
+			} else {
+				printf ("fail with code %x\n", status);
+				_delay_ms (1000);
+			}
+		}
+		printf ("%i/%i/%i\n", (val[1] << 8) | val[0], (val[3] << 8) | val[2], (val[5] << 8) | val[4]);
+	}
+
+	while (1);
+}
-- 
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