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incubator-nuttx/drivers/i2c/i2c_bitbang.c

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/****************************************************************************
* drivers/i2c/i2c_bitbang.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/irq.h>
#include <nuttx/semaphore.h>
#include <nuttx/kmalloc.h>
#include <nuttx/i2c/i2c_master.h>
#include <nuttx/i2c/i2c_bitbang.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Types
****************************************************************************/
struct i2c_bitbang_dev_s
{
struct i2c_master_s i2c;
struct i2c_bitbang_lower_dev_s *lower;
#ifndef CONFIG_I2C_BITBANG_NO_DELAY
int32_t delay;
#endif
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static int i2c_bitbang_transfer(FAR struct i2c_master_s *dev,
FAR struct i2c_msg_s *msgs, int count);
static int i2c_bitbang_set_scl(FAR struct i2c_bitbang_dev_s *dev,
bool high, bool nodelay);
static void i2c_bitbang_set_sda(FAR struct i2c_bitbang_dev_s *dev,
bool high);
static int i2c_bitbang_wait_ack(FAR struct i2c_bitbang_dev_s *dev);
static void i2c_bitbang_send(FAR struct i2c_bitbang_dev_s *dev,
uint8_t data);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct i2c_ops_s g_i2c_ops =
{
.transfer = i2c_bitbang_transfer
};
/****************************************************************************
* Inline Functions
****************************************************************************/
inline static bool i2c_bitbang_get_sda(FAR struct i2c_bitbang_dev_s *dev)
{
return dev->lower->ops->get_sda(dev->lower);
}
#ifdef CONFIG_I2C_BITBANG_CLOCK_STRETCHING
inline static bool i2c_bitbang_get_scl(FAR struct i2c_bitbang_dev_s *dev)
{
return dev->lower->ops->get_scl(dev->lower);
}
#endif
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: i2c_bitbang_transfer
****************************************************************************/
static int i2c_bitbang_transfer(FAR struct i2c_master_s *dev,
FAR struct i2c_msg_s *msgs, int count)
{
FAR struct i2c_bitbang_dev_s *priv = (FAR struct i2c_bitbang_dev_s *)dev;
int ret = OK;
int i;
irqstate_t flags;
/* Lock to enforce timings */
flags = spin_lock_irqsave();
for (i = 0; i < count; i++)
{
uint8_t addr;
FAR struct i2c_msg_s *msg = &msgs[i];
#ifndef CONFIG_I2C_BITBANG_NO_DELAY
/* Compute delay from frequency */
priv->delay = (USEC_PER_SEC / (2 * msg->frequency)) -
CONFIG_I2C_BITBANG_GPIO_OVERHEAD;
if (priv->delay < 0)
{
priv->delay = 0;
}
#endif
/* If this is the start of transfer or we're changing sending direction
* from last transfer, send START
*/
if (i == 0 ||
(msgs[i - 1].flags & I2C_M_READ) != (msgs[i].flags & I2C_M_READ))
{
/* Send start bit */
i2c_bitbang_set_scl(priv, true, false);
i2c_bitbang_set_sda(priv, false);
i2c_bitbang_set_scl(priv, false, false);
/* Send the address */
addr = (msg->flags & I2C_M_READ ? I2C_READADDR8(msg->addr) :
I2C_WRITEADDR8(msg->addr));
i2c_bitbang_send(priv, addr);
/* Wait for ACK */
ret = i2c_bitbang_wait_ack(priv);
if (ret < 0)
{
goto out;
}
}
i2c_bitbang_set_scl(priv, false, false);
if (msg->flags & I2C_M_READ)
{
int j;
int k;
for (j = 0; j < msg->length; j++)
{
uint8_t data = 0;
i2c_bitbang_set_sda(priv, true);
msg->buffer[j] = 0;
for (k = 0; k < 8; k++)
{
i2c_bitbang_set_scl(priv, true, false);
data |= (i2c_bitbang_get_sda(priv) & 1) << (7 - k);
i2c_bitbang_set_scl(priv, false, false);
}
msg->buffer[j] = data;
if (j < msg->length - 1)
{
/* Send ACK */
i2c_bitbang_set_sda(priv, false);
i2c_bitbang_set_scl(priv, true, false);
i2c_bitbang_set_scl(priv, false, false);
}
else
{
/* On the last byte send NAK */
i2c_bitbang_set_sda(priv, true);
i2c_bitbang_set_scl(priv, true, false);
i2c_bitbang_set_scl(priv, false, false);
}
}
}
else
{
int j;
for (j = 0; j < msg->length; j++)
{
/* Send the data */
i2c_bitbang_send(priv, msg->buffer[j]);
ret = i2c_bitbang_wait_ack(priv);
if (ret < 0)
{
goto out;
}
i2c_bitbang_set_scl(priv, false, false);
}
}
if (!(msg->flags & I2C_M_NOSTOP))
{
/* Send stop */
i2c_bitbang_set_sda(priv, false);
i2c_bitbang_set_scl(priv, true, true);
i2c_bitbang_set_sda(priv, true);
}
}
out:
/* Ensure lines are released */
i2c_bitbang_set_scl(priv, true, false);
i2c_bitbang_set_sda(priv, true);
spin_unlock_irqrestore(flags);
return ret;
}
/****************************************************************************
* Name: i2c_bitbang_wait_ack
****************************************************************************/
static int i2c_bitbang_wait_ack(FAR struct i2c_bitbang_dev_s *priv)
{
int ret = OK;
int i;
/* Wait for ACK */
i2c_bitbang_set_sda(priv, true);
i2c_bitbang_set_scl(priv, true, true);
for (i = 0; i2c_bitbang_get_sda(priv) &&
i < CONFIG_I2C_BITBANG_TIMEOUT; i++)
{
up_udelay(1);
}
if (i == CONFIG_I2C_BITBANG_TIMEOUT)
{
ret = -EIO;
}
else
{
int remaining = priv->delay - i;
if (remaining > 0)
{
up_udelay(remaining);
}
}
return ret;
}
/****************************************************************************
* Name: i2c_bitbang_send
****************************************************************************/
static void i2c_bitbang_send(FAR struct i2c_bitbang_dev_s *priv,
uint8_t data)
{
uint8_t bit = 0b10000000;
while (bit)
{
i2c_bitbang_set_sda(priv, !!(data & bit));
i2c_bitbang_set_scl(priv, true, false);
i2c_bitbang_set_scl(priv, false, false);
bit >>= 1;
}
}
/****************************************************************************
* Name: i2c_bitbang_set_sda
****************************************************************************/
static void i2c_bitbang_set_sda(FAR struct i2c_bitbang_dev_s *dev, bool high)
{
dev->lower->ops->set_sda(dev->lower, high);
}
/****************************************************************************
* Name: i2c_bitbang_set_scl
****************************************************************************/
static int i2c_bitbang_set_scl(FAR struct i2c_bitbang_dev_s *dev, bool high,
bool nodelay)
{
dev->lower->ops->set_scl(dev->lower, high);
#ifndef CONFIG_I2C_BITBANG_NO_DELAY
if (!nodelay && dev->delay)
{
up_udelay(dev->delay);
}
#endif
#ifdef CONFIG_I2C_BITBANG_CLOCK_STRETCHING
/* Allow for clock stretching */
if (high)
{
int i;
for (i = 0; !i2c_bitbang_get_scl(dev) &&
i < CONFIG_I2C_BITBANG_TIMEOUT; i++)
{
up_udelay(1);
if (i == CONFIG_I2C_BITBANG_TIMEOUT)
{
return -ETIMEDOUT;
}
}
}
#endif
return OK;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: i2c_bitbang_initialize
*
* Description:
* Initialize a bitbang I2C device instance
*
* Input Parameters:
* lower - Lower half of driver
*
* Returned Value:
* Pointer to a the I2C instance
*
****************************************************************************/
FAR struct i2c_master_s *i2c_bitbang_initialize(
FAR struct i2c_bitbang_lower_dev_s *lower)
{
FAR struct i2c_bitbang_dev_s *dev;
DEBUGASSERT(lower && lower->ops);
dev = (FAR struct i2c_bitbang_dev_s *)kmm_zalloc(sizeof(*dev));
if (!dev)
{
return NULL;
}
dev->i2c.ops = &g_i2c_ops;
dev->lower = lower;
dev->lower->ops->initialize(dev->lower);
return &dev->i2c;
}
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