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incubator-nuttx/drivers/analog/mcp3008.c

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/****************************************************************************
* drivers/analog/mcp3008.c
*
* Contributed by Matteo Golin
*
* 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 <assert.h>
#include <debug.h>
#include <errno.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <sys/types.h>
#include <nuttx/analog/adc.h>
#include <nuttx/arch.h>
#include <nuttx/kmalloc.h>
#include <nuttx/spi/spi.h>
#include <nuttx/analog/mcp3008.h>
/****************************************************************************
* Preprocessor definitions
****************************************************************************/
#if !defined(CONFIG_SPI)
#error "SPI Support Required."
#endif
#define MCP3008_NUM_CHANNELS 8
/* 3.6MHz is recommended for VDD >= 4V
* 2.34MHz is recommended for VDD >= 3.3V
* 1.35MHz is recommended for VDD = 2.7V
*/
#ifndef CONFIG_ADC_MCP3008_SPI_FREQUENCY
#define CONFIG_ADC_MCP3008_SPI_FREQUENCY 2340000
#endif /* CONFIG_ADC_MCP3008_SPI_FREQUENCY */
/* Single-ended or differential modes */
#ifndef CONFIG_ADC_MCP3008_DIFFERENTIAL
#define CONFIG_ADC_MCP3008_DIFFERENTIAL 0
#endif /* CONFIG_ADC_MCP3008_DIFFERENTIAL */
#define MCP3008_SPI_MODE (SPIDEV_MODE0)
#if defined(CONFIG_ADC_MCP3008)
/****************************************************************************
* Private Types
****************************************************************************/
struct mcp3008_dev_s
{
FAR struct spi_dev_s *spi; /* SPI interface */
FAR const struct adc_callback_s *cb;
bool diff; /* True if the ADC is in differential mode, false otherwise. */
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/* ADC methods */
static int mcp3008_bind(FAR struct adc_dev_s *dev,
FAR const struct adc_callback_s *callback);
static void mcp3008_reset(FAR struct adc_dev_s *dev);
static int mcp3008_setup(FAR struct adc_dev_s *dev);
static void mcp3008_shutdown(FAR struct adc_dev_s *dev);
static void mcp3008_rxint(FAR struct adc_dev_s *dev, bool enable);
static int mcp3008_ioctl(FAR struct adc_dev_s *dev, int cmd,
unsigned long arg);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct adc_ops_s g_mcp3008ops =
{
.ao_bind = mcp3008_bind,
.ao_reset = mcp3008_reset,
.ao_setup = mcp3008_setup,
.ao_shutdown = mcp3008_shutdown,
.ao_rxint = mcp3008_rxint,
.ao_ioctl = mcp3008_ioctl,
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: mcp3008_configspi
*
* Description:
* Configure the SPI interface for the MCP3008.
*
****************************************************************************/
static inline void mcp3008_configspi(FAR struct spi_dev_s *spi)
{
SPI_SETMODE(spi, MCP3008_SPI_MODE);
SPI_SETBITS(spi, 8);
SPI_HWFEATURES(spi, 0);
SPI_SETFREQUENCY(spi, CONFIG_ADC_MCP3008_SPI_FREQUENCY);
}
/****************************************************************************
* Name: mcp3008_readchannel
*
* Description:
* Read the corresponding channel of the MCP3008 ADC.
*
* Input Parameters:
* priv - An MCP3008 device structure.
* msg - An ADC message struct where the am_channel member contains the
* channel number to be read, and where the am_data member is where the
* reading is stored.
*
* NOTE:
* When single-ended mode is enabled, the channel number will correspond
* directly to the channel number (0-7) on the ADC.
* When differential mode is enabled, the channel numbers will correspond
* to the following differential pairs:
*
* msg->am_channel Source
* 0 CH0+, CH1-
* 1 CH0-, CH1+
* 2 CH2+, CH3-
* 3 CH2-, CH3+
* 4 CH4+, CH5-
* 5 CH4-, CH5+
* 6 CH6+, CH7-
* 7 CH6-, CH7+
*
****************************************************************************/
static int mcp3008_readchannel(FAR struct mcp3008_dev_s *priv,
FAR struct adc_msg_s *msg)
{
/* First byte is 0s followed by start byte.
* Second byte is control bits, set later.
* Third byte contents do not matter, but are 0 here.
*
* When data is received into this buffer:
* First byte is garbage.
* Second and third byte contain b9-b0.
*/
uint8_t data[3] =
{
1, 0, 0
};
DEBUGASSERT(priv != NULL);
DEBUGASSERT(msg != NULL);
if (priv->diff)
{
data[1] = 0x0; /* Differential control bits start with 0 in MSB. */
}
else
{
data[1] = 0x8; /* Single-ended control bits start with 1 in MSB. */
}
/* Only get last three bits of the channel since there are only 8 channels.
*/
data[1] |= (msg->am_channel & 0x7);
data[1] <<= 4;
/* Send control message */
SPI_LOCK(priv->spi, true);
mcp3008_configspi(priv->spi);
SPI_SELECT(priv->spi, SPIDEV_ADC(0), true);
SPI_EXCHANGE(priv->spi, data, data, sizeof(data));
SPI_SELECT(priv->spi, SPIDEV_ADC(0), false);
SPI_LOCK(priv->spi, false);
/* Mask out anything not part of the 10 measurement bits */
msg->am_data = ((data[1] & 3) << 8) + (data[2]);
return 0;
}
/****************************************************************************
* Name: mcp3008_bind
*
* Description:
* Bind the upper-half driver callbacks to the lower-half implementation.
* This must be called early in order to receive ADC event notifications.
*
****************************************************************************/
static int mcp3008_bind(FAR struct adc_dev_s *dev,
FAR const struct adc_callback_s *callback)
{
FAR struct mcp3008_dev_s *priv = (FAR struct mcp3008_dev_s *)dev->ad_priv;
DEBUGASSERT(priv != NULL);
priv->cb = callback;
return 0;
}
/****************************************************************************
* Name: mcp3008_reset
*
* Description:
* Reset the ADC device. Called early to initialize the hardware. This
* is called, before ao_setup() and on error conditions.
* The MCP3008 can't be reset, nothing needs to be done here.
*
****************************************************************************/
static void mcp3008_reset(FAR struct adc_dev_s *dev)
{
}
/****************************************************************************
* Name: mcp3008_setup
*
* Description:
* Configure the ADC. This method is called the first time that the ADC
* device is opened.
* MCP3008 runs as soon as it is powered. There is no setup required.
*
****************************************************************************/
static int mcp3008_setup(FAR struct adc_dev_s *dev)
{
return OK;
}
/****************************************************************************
* Name: mcp3008_shutdown
*
* Description:
* Disable the ADC. This method is called when the ADC device is closed.
* This method should reverse the operation of the setup method.
* The MCP3008 cannot be shutdown unless powered off, so nothing is
* required.
*
****************************************************************************/
static void mcp3008_shutdown(FAR struct adc_dev_s *dev)
{
}
/****************************************************************************
* Name: mcp3008_rxint
*
* Description:
* Needed for ADC upper-half compatibility but conversion interrupts
* are not supported by the MCP3008.
*
****************************************************************************/
static void mcp3008_rxint(FAR struct adc_dev_s *dev, bool enable)
{
}
/****************************************************************************
* Name: mcp3008_ioctl
*
* Description:
* All ioctl calls will be routed through this method.
*
****************************************************************************/
static int mcp3008_ioctl(FAR struct adc_dev_s *dev, int cmd,
unsigned long arg)
{
FAR struct mcp3008_dev_s *priv = (FAR struct mcp3008_dev_s *)dev->ad_priv;
int ret = 0;
switch (cmd)
{
/* Trigger a measurement */
case ANIOC_TRIGGER:
{
struct adc_msg_s msg;
for (uint8_t i = 0; i < MCP3008_NUM_CHANNELS && (ret == 0); i++)
{
msg.am_channel = i;
ret = mcp3008_readchannel(priv, &msg);
if (ret == 0)
{
priv->cb->au_receive(dev, i, msg.am_data);
}
}
} break;
/* Change differential mode */
case ANIOC_MCP3008_DIFF:
DEBUGASSERT(arg == 0 || arg == 1);
priv->diff = arg;
break;
/* Get the number of channels */
case ANIOC_GET_NCHANNELS:
ret = 8;
break;
/* Command was not recognized */
default:
ret = -EINVAL;
aerr("MCP3008 ioctl: Unrecognized cmd: %d\n", cmd);
break;
}
return ret;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: mcp3008_initialize
*
* Description:
* Initialize ADC
*
* Input Parameters:
* spi - SPI driver instance
* spidev - SPI chip select number
*
* Returned Value:
* Valid MCP3008 ADC device structure reference on success; a NULL on
* failure
*
****************************************************************************/
FAR struct adc_dev_s *mcp3008_initialize(FAR struct spi_dev_s *spi)
{
FAR struct mcp3008_dev_s *priv;
FAR struct adc_dev_s *adcdev;
DEBUGASSERT(spi != NULL);
/* Initialize the ADC device structure */
priv = kmm_malloc(sizeof(struct mcp3008_dev_s));
if (priv == NULL)
{
aerr("ERROR: Failed to allocate mcp3008_dev_s instance\n");
free(priv);
return NULL;
}
/* Initialize the MCP3008 device structure */
priv->cb = NULL;
priv->spi = spi;
priv->diff = CONFIG_ADC_MCP3008_DIFFERENTIAL;
adcdev = kmm_malloc(sizeof(struct adc_dev_s));
if (adcdev == NULL)
{
aerr("ERROR: Failed to allocate adc_dev_s instance\n");
return NULL;
}
memset(adcdev, 0, sizeof(struct adc_dev_s));
adcdev->ad_ops = &g_mcp3008ops;
adcdev->ad_priv = priv;
return adcdev;
}
#endif /* CONFIG_ADC_MCP3008 */
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