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adc: Implement ADC driver interface for MCP3008 over SPI. Includes documentation page for the driver, and inclusion of driver registration code for RP2040-based boards.
This commit is contained in:
Matteo Golin
Xiang Xiao
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/****************************************************************************
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* drivers/analog/mcp3008.c
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*
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* Contributed by Matteo Golin
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <assert.h>
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#include <debug.h>
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#include <errno.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <sys/types.h>
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#include <nuttx/analog/adc.h>
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#include <nuttx/arch.h>
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#include <nuttx/kmalloc.h>
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#include <nuttx/spi/spi.h>
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#include <nuttx/analog/mcp3008.h>
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/****************************************************************************
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* Preprocessor definitions
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****************************************************************************/
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#if !defined(CONFIG_SPI)
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#error "SPI Support Required."
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#endif
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#define MCP3008_NUM_CHANNELS 8
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/* 3.6MHz is recommended for VDD >= 4V
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* 2.34MHz is recommended for VDD >= 3.3V
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* 1.35MHz is recommended for VDD = 2.7V
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*/
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#ifndef CONFIG_ADC_MCP3008_SPI_FREQUENCY
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#define CONFIG_ADC_MCP3008_SPI_FREQUENCY 2340000
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#endif /* CONFIG_ADC_MCP3008_SPI_FREQUENCY */
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/* Single-ended or differential modes */
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#ifndef CONFIG_ADC_MCP3008_DIFFERENTIAL
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#define CONFIG_ADC_MCP3008_DIFFERENTIAL 0
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#endif /* CONFIG_ADC_MCP3008_DIFFERENTIAL */
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#define MCP3008_SPI_MODE (SPIDEV_MODE0)
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#if defined(CONFIG_ADC_MCP3008)
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/****************************************************************************
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* Private Types
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****************************************************************************/
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struct mcp3008_dev_s
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{
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FAR struct spi_dev_s *spi; /* SPI interface */
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FAR const struct adc_callback_s *cb;
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bool diff; /* True if the ADC is in differential mode, false otherwise. */
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};
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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/* ADC methods */
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static int mcp3008_bind(FAR struct adc_dev_s *dev,
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FAR const struct adc_callback_s *callback);
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static void mcp3008_reset(FAR struct adc_dev_s *dev);
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static int mcp3008_setup(FAR struct adc_dev_s *dev);
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static void mcp3008_shutdown(FAR struct adc_dev_s *dev);
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static void mcp3008_rxint(FAR struct adc_dev_s *dev, bool enable);
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static int mcp3008_ioctl(FAR struct adc_dev_s *dev, int cmd,
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unsigned long arg);
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static const struct adc_ops_s g_mcp3008ops =
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{
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.ao_bind = mcp3008_bind,
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.ao_reset = mcp3008_reset,
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.ao_setup = mcp3008_setup,
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.ao_shutdown = mcp3008_shutdown,
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.ao_rxint = mcp3008_rxint,
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.ao_ioctl = mcp3008_ioctl,
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};
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: mcp3008_configspi
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*
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* Description:
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* Configure the SPI interface for the MCP3008.
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*
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****************************************************************************/
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static inline void mcp3008_configspi(FAR struct spi_dev_s *spi)
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{
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SPI_SETMODE(spi, MCP3008_SPI_MODE);
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SPI_SETBITS(spi, 8);
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SPI_HWFEATURES(spi, 0);
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SPI_SETFREQUENCY(spi, CONFIG_ADC_MCP3008_SPI_FREQUENCY);
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}
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/****************************************************************************
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* Name: mcp3008_readchannel
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*
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* Description:
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* Read the corresponding channel of the MCP3008 ADC.
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*
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* Input Parameters:
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* priv - An MCP3008 device structure.
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* msg - An ADC message struct where the am_channel member contains the
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* channel number to be read, and where the am_data member is where the
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* reading is stored.
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*
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* NOTE:
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* When single-ended mode is enabled, the channel number will correspond
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* directly to the channel number (0-7) on the ADC.
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* When differential mode is enabled, the channel numbers will correspond
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* to the following differential pairs:
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*
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* msg->am_channel Source
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* 0 CH0+, CH1-
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* 1 CH0-, CH1+
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* 2 CH2+, CH3-
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* 3 CH2-, CH3+
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* 4 CH4+, CH5-
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* 5 CH4-, CH5+
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* 6 CH6+, CH7-
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* 7 CH6-, CH7+
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*
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****************************************************************************/
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static int mcp3008_readchannel(FAR struct mcp3008_dev_s *priv,
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FAR struct adc_msg_s *msg)
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{
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/* First byte is 0s followed by start byte.
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* Second byte is control bits, set later.
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* Third byte contents do not matter, but are 0 here.
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*
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* When data is received into this buffer:
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* First byte is garbage.
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* Second and third byte contain b9-b0.
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*/
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uint8_t data[3] =
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{
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1, 0, 0
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};
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DEBUGASSERT(priv != NULL);
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DEBUGASSERT(msg != NULL);
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if (priv->diff)
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{
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data[1] = 0x0; /* Differential control bits start with 0 in MSB. */
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}
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else
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{
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data[1] = 0x8; /* Single-ended control bits start with 1 in MSB. */
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}
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/* Only get last three bits of the channel since there are only 8 channels.
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*/
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data[1] |= (msg->am_channel & 0x7);
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data[1] <<= 4;
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/* Send control message */
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SPI_LOCK(priv->spi, true);
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mcp3008_configspi(priv->spi);
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SPI_SELECT(priv->spi, SPIDEV_ADC(0), true);
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SPI_EXCHANGE(priv->spi, data, data, sizeof(data));
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SPI_SELECT(priv->spi, SPIDEV_ADC(0), false);
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SPI_LOCK(priv->spi, false);
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/* Mask out anything not part of the 10 measurement bits */
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msg->am_data = ((data[1] & 3) << 8) + (data[2]);
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return 0;
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}
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/****************************************************************************
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* Name: mcp3008_bind
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*
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* Description:
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* Bind the upper-half driver callbacks to the lower-half implementation.
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* This must be called early in order to receive ADC event notifications.
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*
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****************************************************************************/
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static int mcp3008_bind(FAR struct adc_dev_s *dev,
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FAR const struct adc_callback_s *callback)
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{
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FAR struct mcp3008_dev_s *priv = (FAR struct mcp3008_dev_s *)dev->ad_priv;
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DEBUGASSERT(priv != NULL);
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priv->cb = callback;
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return 0;
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}
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/****************************************************************************
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* Name: mcp3008_reset
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*
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* Description:
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* Reset the ADC device. Called early to initialize the hardware. This
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* is called, before ao_setup() and on error conditions.
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* The MCP3008 can't be reset, nothing needs to be done here.
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*
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****************************************************************************/
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static void mcp3008_reset(FAR struct adc_dev_s *dev)
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{
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}
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/****************************************************************************
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* Name: mcp3008_setup
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*
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* Description:
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* Configure the ADC. This method is called the first time that the ADC
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* device is opened.
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* MCP3008 runs as soon as it is powered. There is no setup required.
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*
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****************************************************************************/
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static int mcp3008_setup(FAR struct adc_dev_s *dev)
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{
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return OK;
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}
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/****************************************************************************
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* Name: mcp3008_shutdown
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*
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* Description:
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* Disable the ADC. This method is called when the ADC device is closed.
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* This method should reverse the operation of the setup method.
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* The MCP3008 cannot be shutdown unless powered off, so nothing is
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* required.
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*
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****************************************************************************/
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static void mcp3008_shutdown(FAR struct adc_dev_s *dev)
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{
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}
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/****************************************************************************
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* Name: mcp3008_rxint
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*
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* Description:
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* Needed for ADC upper-half compatibility but conversion interrupts
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* are not supported by the MCP3008.
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*
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****************************************************************************/
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static void mcp3008_rxint(FAR struct adc_dev_s *dev, bool enable)
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{
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}
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/****************************************************************************
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* Name: mcp3008_ioctl
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*
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* Description:
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* All ioctl calls will be routed through this method.
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*
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****************************************************************************/
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static int mcp3008_ioctl(FAR struct adc_dev_s *dev, int cmd,
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unsigned long arg)
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{
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FAR struct mcp3008_dev_s *priv = (FAR struct mcp3008_dev_s *)dev->ad_priv;
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int ret = 0;
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switch (cmd)
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{
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/* Trigger a measurement */
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case ANIOC_TRIGGER:
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{
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struct adc_msg_s msg;
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for (uint8_t i = 0; i < MCP3008_NUM_CHANNELS && (ret == 0); i++)
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{
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msg.am_channel = i;
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ret = mcp3008_readchannel(priv, &msg);
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if (ret == 0)
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{
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priv->cb->au_receive(dev, i, msg.am_data);
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}
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}
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} break;
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/* Change differential mode */
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case ANIOC_MCP3008_DIFF:
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DEBUGASSERT(arg == 0 || arg == 1);
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priv->diff = arg;
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break;
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/* Get the number of channels */
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case ANIOC_GET_NCHANNELS:
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ret = 8;
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break;
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/* Command was not recognized */
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default:
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ret = -EINVAL;
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aerr("MCP3008 ioctl: Unrecognized cmd: %d\n", cmd);
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break;
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}
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return ret;
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: mcp3008_initialize
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*
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* Description:
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* Initialize ADC
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*
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* Input Parameters:
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* spi - SPI driver instance
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* spidev - SPI chip select number
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*
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* Returned Value:
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* Valid MCP3008 ADC device structure reference on success; a NULL on
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* failure
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*
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****************************************************************************/
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FAR struct adc_dev_s *mcp3008_initialize(FAR struct spi_dev_s *spi)
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{
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FAR struct mcp3008_dev_s *priv;
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FAR struct adc_dev_s *adcdev;
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DEBUGASSERT(spi != NULL);
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/* Initialize the ADC device structure */
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priv = kmm_malloc(sizeof(struct mcp3008_dev_s));
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if (priv == NULL)
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{
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aerr("ERROR: Failed to allocate mcp3008_dev_s instance\n");
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free(priv);
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return NULL;
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}
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/* Initialize the MCP3008 device structure */
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priv->cb = NULL;
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priv->spi = spi;
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priv->diff = CONFIG_ADC_MCP3008_DIFFERENTIAL;
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adcdev = kmm_malloc(sizeof(struct adc_dev_s));
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if (adcdev == NULL)
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{
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aerr("ERROR: Failed to allocate adc_dev_s instance\n");
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return NULL;
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}
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memset(adcdev, 0, sizeof(struct adc_dev_s));
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adcdev->ad_ops = &g_mcp3008ops;
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adcdev->ad_priv = priv;
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return adcdev;
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}
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#endif /* CONFIG_ADC_MCP3008 */
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