X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=src%2Fattiny%2Fao_i2c_attiny.c;fp=src%2Fattiny%2Fao_i2c_attiny.c;h=2ee44fd2eea07d180224d077172b220ff8096784;hb=64500ab11ab76d2309608f8e02a1dd9658963b3e;hp=0000000000000000000000000000000000000000;hpb=16bad3b6ab65cf31b19152127cb6af69142c5c12;p=fw%2Faltos

diff --git a/src/attiny/ao_i2c_attiny.c b/src/attiny/ao_i2c_attiny.c
new file mode 100644
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--- /dev/null
+++ b/src/attiny/ao_i2c_attiny.c
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+/*
+ * Copyright © 2011 Keith Packard <keithp@keithp.com>
+ *
+ * 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 2 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, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include <ao.h>
+
+/*
+ * ATtiny USI as an I2C interface
+ */
+
+#define I2C_USICR ((0 << USISIE) |	/* No start condition interrupt */ \
+		   (0 << USIOIE) |	/* No counter overflow interrupt */ \
+		   (1 << USIWM1) |	/* Two-wire mode */		\
+		   (0 << USIWM0) |	/*   ... */			\
+		   (1 << USICS1) |	/* Software clock strobe */	\
+		   (0 << USICS0) |	/*   ... */			\
+		   (1 << USICLK))	/*   ... */			\
+
+#define I2C_USICR_TICK (I2C_USICR | (1 << USITC))	/* Toggle the clock on every write */
+
+#define I2C_USISR_1BIT	((1<<USISIF)|	/* Clear start condition flag */ \
+			 (1<<USIOIF)|	/* Clear overflow flag */	\
+			 (1<<USIPF)|	/* Clear stop condition flag */	\
+			 (1<<USIDC)|	/* Clear data collision flag */	\
+			 (0xE<<USICNT0)) /* Set counter value to 0xe */
+
+#define I2C_USISR_8BIT	((1<<USISIF)|	/* Clear start condition flag */ \
+			 (1<<USIOIF)|	/* Clear overflow flag */	\
+			 (1<<USIPF)|	/* Clear stop condition flag */	\
+			 (1<<USIDC)|	/* Clear data collision flag */	\
+			 (0x0<<USICNT0)) /* Set counter value to 0 */
+
+#define T2_TWI    5 		/* >4.7μs */
+#define T4_TWI    4 		/* >4.0μs */
+
+static inline void ao_i2c_transfer(uint8_t sr)
+{
+	USISR = sr;
+	for (;;) {
+		ao_delay_us(T2_TWI);
+
+		/* Clock high */
+		USICR = I2C_USICR_TICK;
+
+		/* Wait for clock high (clock stretching) */
+		ao_delay_us(T4_TWI);
+		while(!(I2C_PIN & (1<<I2C_PIN_SCL)))
+			;
+
+		/* Clock low */
+		USICR = I2C_USICR_TICK;
+
+		/* Check for transfer complete */
+		if (USISR & (1 << USIOIF))
+			break;
+	}
+	ao_delay_us(T2_TWI);
+}
+
+static inline uint8_t ao_i2c_get_byte(uint8_t sr)
+{
+	uint8_t	ret;
+
+	/* Set SDA to input */
+	I2C_DIR &= ~(1<<I2C_PIN_SDA);
+
+	ao_i2c_transfer(sr);
+
+	ret = USIDR;
+	USIDR = 0xff;
+
+	/* Set SDA to output */
+	I2C_DIR |= (1<<I2C_PIN_SDA);
+
+	return ret;
+}
+
+static uint8_t
+ao_i2c_write_byte(uint8_t byte)
+{
+	/* Pull SCL low */
+	I2C_PORT &= ~(1<<I2C_PIN_SCL);
+
+	/* Write the byte */
+	USIDR = byte;
+      
+	/* Clock and verify (N)ACK from slave */
+
+	ao_i2c_transfer(I2C_USISR_8BIT);
+
+	if (ao_i2c_get_byte(I2C_USISR_1BIT) & 0x80)
+		return 0;
+
+	return 1;
+}
+
+static uint8_t
+ao_i2c_read_byte(uint8_t ack)
+{
+	uint8_t	ret;
+
+	/* Read the data */
+	ret = ao_i2c_get_byte(I2C_USISR_8BIT);
+
+	/* Ack it */
+	USIDR = ack;
+	ao_i2c_transfer(I2C_USISR_8BIT);
+
+	return ret;
+}
+
+uint8_t
+ao_i2c_start_bus(uint8_t address)
+{
+	/* Release SCL to ensure that (repeated) Start can be performed */
+
+	I2C_PORT |= (1<<I2C_PIN_SCL);
+
+	while( !(I2C_PORT & (1<<I2C_PIN_SCL)) )
+		;
+	ao_delay_us(T2_TWI);
+
+	/* Generate Start Condition */
+
+	/* Pull SDA low */
+	I2C_PORT &= ~(1<<I2C_PIN_SDA);
+	ao_delay_us(T4_TWI);                         
+
+	/* Pull SCL low */
+	I2C_PORT &= ~(1<<I2C_PIN_SCL);
+
+	/* Raise SDA */
+	I2C_PORT |= (1<<I2C_PIN_SDA);
+
+	return ao_i2c_write_byte(address);
+}
+
+static void
+ao_i2c_stop_bus(void)
+{
+	/* Pull SDA low. */
+	I2C_PORT &= ~(1<<I2C_PIN_SDA);
+
+	/* Release SCL. */
+	I2C_PORT |= (1<<I2C_PIN_SCL);
+
+	/* Wait for SCL to go high */
+	while( !(I2C_PIN & (1<<I2C_PIN_SCL)) );
+	ao_delay_us(T4_TWI);
+
+	/* Raise SDA */
+	I2C_PORT |= (1<<I2C_PIN_SDA);
+	ao_delay_us(T2_TWI);
+}
+
+/* Send bytes over SPI.
+ *
+ * This just polls; the SPI is set to go as fast as possible,
+ * so using interrupts would take way too long
+ */
+uint8_t
+ao_i2c_send_bus(void __xdata *block, uint16_t len, uint8_t stop)
+{
+	uint8_t	*d = block;
+
+	while (len--)
+		if (!ao_i2c_write_byte (*d++))
+			return 0;
+	if (stop)
+		ao_i2c_stop_bus();
+	return 1;
+}
+
+/* Send bytes over SPI.
+ *
+ * This just polls; the SPI is set to go as fast as possible,
+ * so using interrupts would take way too long
+ */
+uint8_t
+ao_i2c_send_fixed_bus(uint8_t d, uint16_t len, uint8_t stop)
+{
+	while (len--)
+		if (!ao_i2c_write_byte (d))
+			return 0;
+	if (stop)
+		ao_i2c_stop_bus();
+	return 1;
+}
+
+/* Receive bytes over SPI.
+ *
+ * Poll, sending zeros and reading data back
+ */
+uint8_t
+ao_i2c_recv_bus(void __xdata *block, uint16_t len, uint8_t stop)
+{
+	uint8_t	*d = block;
+
+	while (len--)
+		*d++ = ao_i2c_read_byte (len ? 0x00 : 0xff);
+	if (stop)
+		ao_i2c_stop_bus();
+	return 1;
+}
+
+/*
+ * Initialize USI
+ *
+ * Chip select is the responsibility of the caller
+ */
+
+void
+ao_i2c_init(void)
+{
+	/* Pull-ups on SDA and SCL */
+	I2C_PORT |= (1<<I2C_PIN_SDA);
+	I2C_PORT |= (1<<I2C_PIN_SCL);
+  
+	/* SCL and SDA are outputs */
+	I2C_DIR  |= (1<<I2C_PIN_SCL);
+	I2C_DIR  |= (1<<I2C_PIN_SDA);
+  
+	USIDR =  0xFF;
+	USICR =  I2C_USICR;
+}