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AD7193 - No-OS Driver for Microchip Microcontroller Platforms

Supported devices

Evaluation Boards

Overview

The AD719X family is composed of a low noise, complete analog front end for high precision measurement applications. It contains a low noise, 24-bit sigma-delta (Σ-Δ) analog-to-digital converter (ADC). The on-chip low noise gain stage means that signals of small amplitude can interface directly to the ADC.

The on-chip channel sequencer allows several channels to be enabled simultaneously, and the AD719X sequentially converts on each enabled channel, simplifying communication with the part. The on-chip 4.92 MHz clock can be used as the clock source to the ADC or, alternatively, an external clock or crystal can be used. The output data rate from the part can be varied from 4.7 Hz to 4.8 kHz.

The device has a very flexible digital filter, including a fast settling option. Variables such as output data rate and settling time are dependent on the option selected. The AD7193 also includes a zero latency option.

AD7190 operates with 5 V analog power supply and a digital power supply from 2.7 V to 5.25 V. It consumes a current of 6 mA. It is housed in a 24-lead TSSOP package.

AD7192 operates with a power supply from 3 V to 5.25 V. It consumes a current of 4.35 mA. It is housed in a 24-lead TSSOP package.

AD7193 operates with a power supply from 3 V to 5.25 V. It consumes a current of 4.65 mA, and it is available in a 28-lead TSSOP package and a 32-lead LFCSP package.

AD7194 operates with a power supply from 3 V to 5.25 V. It consumes a current of 4.65 mA, and it is housed in a 32-lead LFCSP package.

AD7195 operates with a 5 V analog power supply and a digital power supply from 2.7 V to 5.25 V. It consumes a current of 6 mA. It is housed in a 32-lead LFCSP package.

Applications

Weigh scales
Strain gage transducers
Pressure measurement
Pressure measurement
Temperature measurement
Chromatography
PLC/DCS analog input modules
Data acquisition
Medical and scientific instrumentation

ADI No-OS

The goal of ADI Microcontroller No-OS is to be able to provide reference projects for lower end processors, which can't run Linux, or aren't running a specific operating system, to help those customers using microcontrollers with ADI parts. ADI No-OS offers generic drivers which can be used as a base for any microcontroller platform and also example projects which are using these drivers on various microcontroller platforms.

For more information about ADI No-OS and supported microcontroller platforms see: no-OS

Driver Description

The source code for AD719X driver can be found here:

The driver also uses the ADI util library, so make sure you also add the necessary files in your project. The source code for the util library can be found here:

The driver contains three parts:

The driver for the AD719X part, which may be used, without modifications, with any microcontroller.
The Communication Driver, where the specific communication functions for the desired type of processor and communication protocol have to be implemented. This driver implements the communication with the device and hides the actual details of the communication protocol to the ADI driver.
The GPIO Driver, where the specific GPIO functions for the desired type of processor have to be implemented. This driver lets the device know when the conversions are ready, hiding the actual details of the GPIO ADI driver.

The Communication and GPIO drivers have a standard interface, so the AD719X driver can be used exactly as it is provided.

For SPI Communication there are three functions which are called by the AD719X driver:

no_os_spi_init() – Initializes the communication peripheral.
no_os_spi_write_and_read() - Reads and writes data from/to device.
no_os_spi_remove() - Removes SPI device.

SPI driver architecture

For GPIO control there are seven functions which are called by the AD719X driver:

no_os_gpio_get() – Initializes GPIO peripheral.
no_os_gpio_get_optional() - Initializes optional GPIO peripheral.
no_os_gpio_direction_input() - Sets GPIO as input.
no_os_gpio_direction_output - Sets GPIO as output
no_os_gpio_get_value - Gets value of GPIO.
no_os_gpio_set_value - Sets value of GPIO.
no_os_gpio_remove - Removes GPIO peripheral.

For SPI and GPIO usage there are four data types that have to be defined:

no_os_spi_desc - structure holding the SPI descriptor
no_os_spi_init_param - structure holding the parameters for SPI initialization
no_os_gpio_desc - structure holding the GPIO descriptor
no_os_gpio_init_param - structure holding the parameters for GPIO initialization

AD719X Driver Code Documentation

Source code documentation for the driver is automatically generated using the Doxygen tool and it is available below:

AD719X Device Configuration

Driver Initialization

In order to be able to use the device, you will have to provide the initial parameters for the communication protocol as for the device - spi initial parameters, gpio MISO initial parameters, gpio SYNC initial parameters, polarity, gain, operating mode, data rate code, clock source, input mode, buffer option, bpdsw mode and chip id. The first API to be called is ad719x_init. Make sure that it returns 0, which means that the device was initialized correctly. ad719x_init also performs a soft reset, by calling ad719x_reset, in order to put the device in a known state.

Range Configuration

By calling ad719x_range_setup, driver sets polarity and gain of the device. Accepted values for gain:

AD719X_ADC_GAIN_1
AD719X_ADC_GAIN_8
AD719X_ADC_GAIN_16
AD719X_ADC_GAIN_32
AD719X_ADC_GAIN_64
AD719X_ADC_GAIN_128

Filter Output Data Rate Configuration

By calling ad719x_output_rate_select, driver sets the filter output data rate. Accepted values are between 1 and 1023. The output data rate can be programmed from 4.7 Hz to 4800 Hz.

Buffer Configuration

By calling ad719x_buffer_select, driver sets the inputs as buffered or unbuffered.

Clock Configuration

By calling ad719x_clock_select, driver sets the clock source for the ADC. Accepted values:

AD719X_EXT_CRYSTAL_MCLK1_MCLK2 - External crystal. The external crystal is connected from MCLK1 to MCLK2.
AD719X_EXT_CRYSTAL_MCLK2 - External Clock applied to MCLK2.
AD719X_INT_CLK_4_92_MHZ_TRIST - Internal 4.92 MHz clock. Pin MCLK2 is tristated.
AD719X_INT_CLK_4_92_MHZ - Internal 4.92 MHz clock. The internal clock is available on MCLK2.

Bridge Switch Configuration

By calling ad719x_set_bridge_switch, driver opens or closes the bridge power-down switch of the ADC.

Operating Mode Configuration

By calling ad719x_set_operating_mode, driver sets ADC to the desired operation mode.

All the above configurations are done by ad719x_init, so no further configuration is needed.

Channel Calibration

Channel calibration can be done calling ad719x_calibrate and providing desired channel and calibration type.

AD719X Device Measurements

Operation Mode Setting

After the specific configuration was performed as mentioned above, you can set the device in the desired measurement mode, using ad719x_set_operating_mode API. The available operation modes are:

AD719X_MODE_CONT - Continuous Conversion Mode
AD719X_MODE_SINGLE - Single Conversion Mode
AD719X_MODE_IDLE - Idle Mode
AD719X_MODE_PWRDN - Power-Down Mode
AD719X_MODE_CAL_INT_ZERO - Internal Zero-Scale Calibration
AD719X_MODE_CAL_INT_FULL - Internal Full-Scale Calibration
AD719X_MODE_CAL_SYS_ZERO - System Zero-Scale Calibration
AD719X_MODE_CAL_SYS_FULL - System Full-Scale Calibration

Temperature Data

Temperature can be read using device's internal sensor. ad719x_temperature_read API will read and convert raw value into Celsius degrees.

Single Conversion Data

By using ad719x_single_conversion API, a single read of the enabled channels will occur.

Continuous Conversion Data

By using ad719x_continuous_read_avg API, the device will read the specified number of samples and will store their average value.

For Single Conversion and Continuous Conversion Data, user can use ad719x_convert_to_volts API to transform raw value into Volts.

AD719X Driver Initialization Example on Xilinx Platform

struct xil_spi_init_param spi_extra = {
	.type = SPI_PS,
	.flags = 0U
};
struct spi_init_param spi_ip = {
	.device_id = SPI_DEVICE_ID,
	.max_speed_hz = 1000,
	.mode = SPI_MODE_3,
	.chip_select = 0U,
	.bit_order = SPI_BIT_ORDER_MSB_FIRST,
	.platform_ops = &xil_spi_ops,
	.extra = &spi_extra
};

const struct xil_gpio_init_param gpio_extra = {
	.type = GPIO_PS,
	.device_id = GPIO_DEVICE_ID
};
const struct gpio_init_param miso_ip = {
	.number = RDY_PIN,
	.platform_ops = &xil_gpio_ops,
	.extra = &gpio_extra
};
const struct gpio_init_param sync_ip = {
	.number = SYNC_PIN,
	.platform_ops = &xil_gpio_ops,
	.extra = &gpio_extra
};

/* Device AD719X instance. */
struct ad719x_dev *dev;
struct ad719x_init_param ad7190_dev_ip = {
	.spi_init = &spi_ip,
	.gpio_miso = &miso_ip,
	.sync_pin = NULL,
	.current_polarity = 1,
	.current_gain = AD719X_ADC_GAIN_64,
	.operating_mode = AD719X_MODE_SINGLE,
	.data_rate_code = 480U,
	.clock_source = AD719X_INT_CLK_4_92_MHZ,
	.input_mode = 0,
	.buffer = 0,
	.bpdsw_mode = 0,
	.chip_id = AD7190
};

ret = ad719x_init(&dev, ad7190_dev_ip);
if(ret)
	return FAILURE;

01 Oct 2012 15:09 · Dragos Bogdan

HW Platform(s):

Downloads

AD7193 DSPIC33 Driver
AD7193 chipKIT Driver
AD7193 Driver: https://github.com/analogdevicesinc/no-OS/tree/master/drivers/AD7193
PmodAD5 Demo for PIC32MX320F128H: https://github.com/analogdevicesinc/no-OS/tree/master/Microchip/PIC32MX320F128H/PmodAD5
PIC32MX320F128H Common Drivers: https://github.com/analogdevicesinc/no-OS/tree/master/Microchip/PIC32MX320F128H/Common

Digilent Cerebot MX3cK Quick Start Guide

This section contains a description of the steps required to run the AD7193 demonstration project on a Digilent Cerebot MX3cK platform.

Required Hardware

Required Software

MPLAB X Integrated Development Environment
MPLAB XC32 compiler
The AD7193 demonstration project for PIC32MX320F128H.

The AD7193 demonstration project for PIC32MX320F128H consists of three parts: the AD7193 Driver, the PmodAD5 Demo for PIC32MX320F128H and the PIC32MX320F128H Common Drivers.

All three parts have to be downloaded.

Hardware Setup

A PmodAD5 has to be connected to the JE connector of Cerebot MX3cK development board.

When using AVDD > DVDD (= 3.3V), JP1 on PmodAD5 must be removed. The range for AVDD is 3.0V ≤ AVDD ≤ 5.25V

Reference Project Overview

The following commands were implemented in this version of AD7193 reference project for Cerebot MX3cK board.

Command	Description
help?	Displays all available commands.
reset=	Resets the AD7193.
polarity?	Displays the polarity value.
polarity=	Sets the polarity value. Accepted values: 0 - Bipolar mode. 1 - Unipolar mode.
range?	Displays the range value.
range=	Sets the range value. Accepted values: 0 - Gain=1. (Input voltage range must be +/-2500mV) 3 - Gain=8. (Input voltage range must be +/-312.5mV) 4 - Gain=16. (Input voltage range must be +/-156.2mV) 5 - Gain=32. (Input voltage range must be +/-78.12mV) 6 - Gain=64. (Input voltage range must be +/-39.06mV) 7 - Gain=128.(Input voltage range must be +/-19.53mV)
pseudoBit?	Displays the Pseudo Bit value (AD7193_REG_CONF).
pseudoBit=	Sets the Pseudo Bit Value (AD7193_REG_CONF). Accepted values: 0 - Disables the pseudo differential measuring. 1 - Enables the pseudo differential measuring.
register?	Displays the value of the data register (AD7193_REG_DATA) for specified channel. Accepted values: 0..7 - selected channel.
voltage?	Displays the voltage applied to specified channel. Accepted values: 0..7 - selected channel.
temperature?	Displays the temperature.

Commands can be executed using a serial terminal connected to the UART1 peripheral of PIC32MX320F128H.

The following image shows a generic list of commands in a serial terminal connected to processor’s UART peripheral.

Software Project Setup

This section presents the steps for developing a software application that will run on the Digilent Cerebot MX3cK development board for controlling and monitoring the operation of the ADI part.

Run the MPLAB X integrated development environment.
Choose to create a new project.
In the Choose Project window select Microchip Embedded category, Standalone Project and press Next.

In the Select Device window choose PIC32MX320F128H device and press Next.

In the Select Tool window select the desired hardware tool and press Next.

In the Select Compiler window chose the XC32 compiler and press Next.

In the Select Project Name and Folder window choose a name and a location for the project.

After the project is created, all the downloaded source files have to be copied in the project folder and included in the project.

The project is ready to be built and downloaded on the development board.

05 Jul 2012 14:45