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diff --git a/firmware/e300/battery/i2c_twi.h b/firmware/e300/battery/i2c_twi.h
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+/* USRP E310 Firmware Atmel AVR TWI driver
+ * Copyright (C) 2014 Ettus Research
+ * This file is part of the USRP E310 Firmware
+ * The USRP E310 Firmware 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.
+ * The USRP E310 Firmware 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 the USRP E310 Firmware. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/**
+ * \file i2c_twi.h
+ * \brief Atmel AVR TWI driver
+ */
+
+#ifndef I2C_TWI_H
+#define I2C_TWI_H
+
+#include <stdlib.h>
+#include <stdio.h>
+
+/**
+ * \brief Used for initializing the TWI/I2C module
+ */
+typedef enum i2c_speed_t {
+	I2C_SPEED_100K,
+	I2C_SPEED_400K,
+} i2c_speed_t;
+
+/**
+ * \brief Initialize and calculate the TWBR value based on F_CPU and given rate
+ *
+ * \param[in] rate Target rate
+ */
+void i2c_twi_init_calc(uint32_t rate);
+
+/**
+ * \brief Initializes the AVR TWI/I2C module
+ *
+ * \param[in] speed Can be either 100KHz or 400Khz
+ */
+void i2c_twi_init(i2c_speed_t speed);
+
+/**
+ * \brief Read I2C register from I2C slave
+ * \param[in] addr I2C slave address
+ * \param[in] reg  Register address in slave register map
+ * \param[out] value Output value
+ * \return 0 on success, negative error code otherwise
+ */
+int8_t i2c_twi_read(uint8_t addr, uint8_t reg, uint8_t *value);
+
+/**
+ * \brief Read 2 byte I2C register from I2C slave
+ *
+ * This is behaving a bit funny but is required for getting
+ * the 2 byte values from the LTC294x chip.
+ *
+ * \param[in] addr I2C slave address
+ * \param[in] reg  Register address in slave register map
+ * \param[out] value Output value
+ * \return 0 on success, negative error code otherwise
+ */
+int8_t i2c_twi_read16(uint8_t addr, uint8_t reg, uint16_t *value);
+
+/**
+ * \brief Write I2C register in I2C slave
+ * \param[in] addr I2C slave address
+ * \param[in] reg  Register address in slave register map
+ * \param[in] value Value to be written
+ * \return 0 on success, negative error code otherwise
+ */
+int8_t i2c_twi_write(uint8_t addr, uint8_t reg, uint8_t value);
+
+/**
+ * \brief Write 2 byte I2C register in I2C slave
+ * \param[in] addr I2C slave address
+ * \param[in] reg  Register address in slave register map
+ * \param[in] value Value to be written
+ * \return 0 on success, negative error code otherwise
+ */
+int8_t i2c_twi_write16(uint8_t addr, uint8_t reg, uint16_t value);
+
+/**
+ * \brief Handle SMBus alert response
+ * \return 0 on success, negative error code otherwise
+ */
+uint8_t i2c_twi_smbus_ara(void);
+
+#endif /* I2C_TWI_H */