MAXREFDES9004 | reference design

Design & Integration File

Designed, Built, Tested

Board pictured here has been fully assembled and tested.

Overview

Design Resources

Design & Integration File

Schematic
PCB Layout
Bill of Materials

Download Design Files 1.13 M

Device Drivers

Software such as C code and/or FPGA code, used to communicate with component's digital interface.

MAX32660 GitHub no-OS Driver Source Code

Description

The DS2485 is a 1-Wire^® master that performs protocol conversion between the I²C master and any attached 1-Wire slaves. For 1-Wire line driving, internal user-adjustable timers relieve the system host processor from generating time-critical 1-Wire waveforms, supporting both standard and overdrive communication speeds. The 1-Wire master has a selectable active or passive 1-Wire pullup. Strong pullup features support 1-Wire power delivery for 1-Wire devices that require additional current such as EEPROM writes or cryptographic operations. The MAXREFDES9004 is a reference design showcasing the DS2485 and its versatility in 1-Wire systems. It includes example design files for connecting an Arm^® Cortex^®-M4 host microcontroller with the DS2485 to communicate with a remotely connected DS28E18 1-Wire slave. It also includes example C-code firmware for supporting Arm Cortex-M4 microcontrollers that demonstrate how to integrate the DS2485 in software.

Features & Benefits

Dedicated 1-Wire Master for Convenient 1-Wire Processing
Up to 100m Remote Communication with Connected 1-Wire Slave Devices
C-Code Demonstrates How to Use the DS2485 in Software Including an Example with the DS28E18

Designed–Built–Tested

A simple, cost-efficient, 1-Wire master is demonstrated using the DS2485 for a simple sensor application using the MAX32660 host microcontroller. This reference design includes the following major components: one each of MAX32660 Cortex-M4 microcontroller, DS2485 1-Wire master, DS28E18 1-Wire to I2C/SPI bridge and an I²C temperature sensor module. This document describes the hardware shown above as well as its supplementing software. It provides a detailed, systematic technical guide to set up and understand the MAXREFDES9004 reference design. The system has been built and tested, details of which follow later in this document.

Important Notice and Disclaimer

Please read the Reference Design Disclaimer for Analog Devices design information and resources.

Product Categories

Processors and Microcontrollers

Parts Used

Details Section

Quick Start Guide

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This section includes a list of recommended equipment and instructions on how to set up the Windows®-based PC for the C-Demo software.

Required Equipment

PC with a Windows 10, Windows 8, or Windows 7 operating system (64-bit or 32-bit) and a spare USB 2.0 or higher port
Low-power Arm Micro Toolchain (Windows)
C-Demo software

Procedure

The reference design is fully assembled and tested. Follow the steps below to set up the demo software:

Download the ARMCortexToolchain.exe file.
In a file viewer (Figure 1), double-click on ARMCortexToolchain.exe to begin the installation.

Figure 1: File Viewer

Follow the prompts on the setup wizard (Figure 2) to finish installation.

Figure 2: Toolchain setup wizard

Figure 2: Toolchain Setup Wizard

Navigate to the toolchain's install directory, open the Eclipse folder, and run Eclipse.bat to launch the Eclipse IDE, as shown in Figure 3.

Figure 3: Eclipse launch location

Figure 3: Eclipse Launch Location

Create a workspace in a desired location, as shown in Figure 4.

Figure 4: Eclipse Workspace Creation

Download MAXREFDES9004 Software and extract the DS2485_C_Demos.zip file, in any location, as shown in Figure 5.

Figure 5: C-Demo Extraction.

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Figure 5: C-Demo Extraction

In Eclipse, go to File\Import... and select Existing Projects into Workspace under the General folder. Click Next > and then Browse... to open the directory browser. Navigate to the C-demo installation directory. Select the extracted folder containing the example programs and click OK. In the panel, check the checkbox next to the desired projects to import. Check the box labelled Copy projects into workspace and click Finish, as shown in Figure 6.

Figure 6: Importing C-Demo Examples

Open up a serial console and connect it to the MAX32660's corresponding serial COM port, as shown in Figure 7.

Figure 7: Opening a Serial Console

Select the example program to run under the drop-down box located next to the green 'Run' button, as shown in Figure 8. The output will be displayed onto the serial console as shown in Figure 9.

Figure 8: Figure 8. Running the Read_Temperature Demo Program

Figure 8: Running the Read_Temperature Demo Program

Figure 9: Console Output for Read_Temperature Demo Program

Detailed Description of Hardware

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Detailed Description of Software

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The MAXREFDES9004 software consists of C-code demonstration programs mainly showcasing the DS2485. See Table 1 for a detailed list of available C-programs. The software is supported on the MAXREFDES9004 hardware and includes the firmware and source files for programming an Arm Cortex-M4 processor-based microcontroller like the MAX32660. This C-Demo software utilizes a DS2485 1-Wire and a DS28E18 API for convenient interfacing within the system. The software is compatible with the Maxim toolchain, that can be found in the design resources tab of the MAX32660 and can be directly imported into an Eclipse IDE workspace. See the Quick Start section for details on how to set up the C-Demo software.

Table 1: Demos Overview
Demo Program	Description
Read_Temperature	Demo program showcasing majority of the DS2485's 1-Wire master features and the reference design hardware from Figure 11. Uses the DS2485-based 1-Wire API and the DS28E18 API to interface with a remote temperature sensor connected to a DS28E18.
One_Wire_Scripting	Demo program showcasing the DS2485's 1-Wire scripting feature specifically. Uses the DS2485-based 1-Wire API to interface the DS2485 with a DS28E18 device.

DS2485 API

Table 2 presents a brief overview of the DS2485 API. This API allows the MAX32660 to interface with the DS2485 through I2C and provides access to each of the DS2485's device function commands.

Table 2. DS2485 API Overview
Function	Description
DS2485_WriteMemory	DS2485 performs a 'Write Memory' command.
DS2485_ReadMemory	DS2485 performs a 'Read Memory' command.
DS2485_ReadStatus	DS2485 performs a 'Read Status' command.
DS2485_SetI²CAddress	DS2485 performs a 'Set I²C Address' command.
DS2485_SetPageProtection	DS2485 performs a 'Set Page Protection' command.
DS2485_ReadOneWirePortConfig	DS2485 performs a 'Read 1-Wire Port Config' command.
DS2485_WriteOneWirePortConfig	DS2485 performs a 'Master Reset' command.
DS2485_MasterReset	DS2485 performs a 'Read Memory' command.
DS2485_OneWireScript	DS2485 performs a '1-Wire Script' command.
DS2485_OneWireBlock	DS2485 performs a '1-Wire Write Block' command.
DS2485_OneWireWriteBlock	DS2485 performs a 'Read Memory' command.
DS2485_OneWireReadBlock	DS2485 performs a '1-Wire Read Block' command.
DS2485_OneWireSearch	DS2485 performs a '1-Wire Search' command.
DS2485_FullCommandSequence	DS2485 performs a 'Full Command Sequence' command.
DS2485_ComputeCrc16	DS2485 performs a 'Compute CRC16' command.

1-Wire API

The 1-Wire API provides full control of the 1-Wire interface. It includes a range of 1-Wire master functionality that is derived from the DS2485 API and is designed to interface with 1-Wire slave devices more easily. An overview of the 1-Wire API is shown in Table 3. See the demo program, "One_Wire_Scripting" for an example of how to use the 1-Wire API to read the DS28E18's device status.

Table 3. 1-Wire API Overview
Function	Description
OneWire_Init	Configures the DS2485 to default settings.
OneWire_ResetPulse	Sends a 1-Wire reset pulse down the 1-Wire bus using the DS2485.
OneWire_WriteByte	Sends a byte down the 1-Wire bus command using the DS2485.
OneWire_WriteBlock	Sends a block of data down the 1-Wire bus using the DS2485.
OneWire_ReadByte	Reads a byte from the 1-Wire bus using the DS2485.
OneWire_ReadBlock	Reads a block of data from the 1-Wire bus using the DS2485.
OneWire_WriteBytePower	Sends a byte down the 1-Wire bus and enables a strong pullup (SPU) immediately thereafter using the DS2485.
OneWire_ReadBytePower	Read a byte from the 1-Wire bus and enables a strong pullup (SPU) immediately thereafter using the DS2485.
OneWire_Search	Searches for slave devices on the 1-Wire bus using the DS2485.
OneWire_Set_OneWireMasterSpeed	Configures the DS2485's 1-Wire Master speed between Standard and Overdrive.
OneWire_Set_tX	Configures a DS2485's 1-Wire Master timing, 'X' (i.e., tRSTL, tMSP, etc.).
OneWire_Enable_APU	Configures the DS2485's 'APU' setting.
OneWire_Enable_SPU	Configures the DS2485's 'SPU' setting.
OneWire_Enable_OneWirePowerDown	Configures the DS2485's 'Power Down' setting.
OneWire_Script_Add_X	Adds a 1-Wire primitive command, 'X' (i.e., OW_RESET, DELAY, etc.) to a global buffer in software.
OneWire_Script_Execute	Performs a '1-Wire Script' command using primitive commands from global buffer in software using the DS2485.

DS28E18 API

The C-Demo software also provides a DS28E18 API. A brief overview of the DS28E18 API is shown in Table 4. This API makes it easy to exercise all the features of the DS28E18 and can be used to integrate multiple I²C and SPI devices into a system. See the demo program, "Read_Temperature," for an example of how to use the DS28E18 API to read a temperature and humidity value from a remote Sensirion SHTC3 I²C sensor.

Table 4. DS28E18 API Overview
Function	Description
DS28E18_Init	Initializes all DS28E18 devices found on the 1-Wire bus.
DS28E18_SetSpeed	Sets the DS28E18 speed between Standard and Overdrive.
DS28E18_WriteSequencer	Writes specified data into the DS28E18 sequencer.
DS28E18_ReadSequencer	Reads specified data from the DS28E18 sequencer.
DS28E18_RunSequencer	Commands DS28E18 to execute specific I2C/SPI sequences from its sequencer.
DS28E18_WriteConfiguration	Configures the DS28E18's general configuration settings.
DS28E18_ReadConfiguration	Reads the DS28E18's general configuration settings.
DS28E18_WriteGpioConfiguration	Configures the DS28E18's GPIO configuration settings.
DS28E18_ReadGpioConfiguration	Reads the DS28E18's GPIO configuration settings.
DS28E18_DeviceStatus	Reads the DS28E18's device status.
DS28E18_BuildPacket_X	Builds 1-Wire packet for Sequencer Command, 'X' (i.e., I²C Start, SENS_VDD On, etc.) and stores it in a global buffer in software. Buffer can be used as a 'DS28E18_Write_sequencer' input.

Documentation & Resources

Design & Integration File

MAXREFDES9004 Design Files
9/13/2021

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1 M

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