LAST UPDATE: 8/2/2019
This is a good example of my "stone knives and bearskins" electronic designs. The objective of this project is to provide a very flexible and capable platform/architecture from commonly available and very low cost electronic modules. Everything is based on open source (free) software. This project will spawn a series of online articles and videos to aid interested persons to learn about embedded systems.
WIFI - I have chosen to use WIFI as a primary interface for most of my wireless projects that require a friendly user interface. The user interface can be presented on a smartphone and and thus eliminates the cost/complexity of fancy displays. This board supports the ESP-01 and Wemos D1 WIFI modules. Note: Other wireless interfaces are also supported by plugging a daughter board into one of the expansion board ports. For example, I have taken into account interfacing to common Radio Control (RC) PWM and PPM signal interfaces, Bluetooth modules, NRF24L01 modules, etc.
Keyboard - The Secondary MCU manages the keyboard interface. This provides flexibility in the keyboard interface design and some Secondary MCU control pins can also be used for other purposes, such as LED lighting.
Speaker - A speaker can be driven directly by the MP3 module. There is also an audio Right and Left channel connector that can be used for stereo output to an external stereo amplifier.
MP3 Player - The MP3 player plays MP3 and WAV files for uses such as, clock chimes, RC model sound kits and of course music. The audio files are stored on a standard micro SD card.
Real-time Clock - The real time clock (RTC) module keeps track of time. It includes a battery backup so the time is retained even if main power is lost. The Primary MCU reads time, calendar and temperature from the RTC with the I2C bus interface. WIFI can be used to obtain the time from the internet and set the clock automatically. The RTC module can also be installed flat instead of standing vertically as shown in the prototype picture.
Secondary MCU - The Secondary MCU ( ATTiny84) manages the keyboard, MP3 module, lighting and potentially other functions. The Secondary MCU presents an I2C bus slave interface to simplify the automatic control of peripherals for the Primary MCU. It can generate an interrupt on the Primary MCU to notify the Primary MCU of events. As an optimization on smaller low-power applications. the Secondary MCU can be configured as an I2C master and eliminate the need for the separate Primary CPU. This case is a good example of a spin-off project based on this board’s architecture.
Primary MCU – The Primary MCU (Arduino Nano) multi-tasks all the main functions for the controller board. For example, it coordinates RTC, motor control, WIFI, and MP3 activities. Coordination is managed by the FreeRTOS real time operating system. Future versions of the board will replace the 8-bit Primary MCU with a much more powerful 32-bit MCU (STM32). NOTE: The motor control drivers are separate and not shown in the prototype photo. The board doesn't need motor control components to implement a simple digital clock as shown.
Power Module - The power module supplies 5v and 3.3v DC power for the board's components.
AC Power is provided by a dirt cheap breadboard friendly module that makes things easy. But, basically there is just a set of power and ground rails on the main board that can accommodate other designs on a daughter board.
Battery power is accommodated by adding a 1s LIPO battery power shield that includes a recharging circuit and provision to monitor the state of charge.
3.3v Option Port - This option port supports the Wemos D1 mini (ESP8266) and shields that have been developed for it for Internet of Things (IOT) applications. The OLED shield is shown in operation on the board. In this case, the Primary MCU is controlling the OLED shield and the WIFI is provided by an ESP-01 instead of a D1. A D1 can be added to provide more capabilities, if necessary. Also, D1 shields (eg. battery shield and others) are supported as low cost options for added capabilities. This board can be thought of as a very big D1 shield for motor control and other applications. The code can be configured to use the D1 as the master on the I2C bus.
Example Clock - The example metal art clock shown is a custom built 3.5 foot diameter clock that was made for the Kaliseum in Kalkaska, MI. Custom clocks like this are driven by the board's stepper motor interface. In the event of a power outage, the board uses hall sensors to locate the clock hands and reposition the hands to display the correct battery backed up time. Clock settings can be done with with WIFI and a smartphone. The MP3 interface provides user configurable chimes. The clock can be powered by AC or a LIPO rechargeable battery.
Example CNC - The CNC example is a small CNC machine that uses stepper motors to drive X, Y and Z axis. The clock example uses 3 stepper motors to control hours, minutes and seconds. The basic hardware and even control code can be the same. Stepper motors and servos that this board controls can also be used in robotics applications.
Future - This board can be used in robotics control, radio control hobbies, home automation and many other purposes through simple reconfiguration of the modules and code. There will be a custom printed circuit board design for this and I will use them on many future projects.
Also, the individual sections of this main board, for example the MP3 player, can serve as a base for smaller educational projects that do not require so many features.
I will be documenting the various optional interfaces and configurations in an effort to provide useful information to all engineers and hobbyists that are interested in embedded systems.
My sincere wish is to help hobbyists learn about electronics and embedded software and to provide entertaining and artistic projects for people to enjoy. I hope I will obtain support for my activities through purchase of items from Checkmate Arts' online store. Purchases should be considered donations that come with a bonus item. The point of Checkmate Arts is to release creativity ... not to be a profitable business enterprise.
As my written articles and video presentations improve, I hope they will become more and more useful and people with like them enough to share them with others.
Doing everything by myself is a massive undertaking... that is, software/firmware development, website, online store, electronic design and testing, mechanical design, CAD/CAM, CNC, 3D printing, metal art, woodworking, manufacturing, sales, marketing, shipping and even the music I played in videos (not that well) is all done by me.
Thank you very much in advance for your support.
Sincerely.
- Jim
James G. Oliver
Owner: Checkmate Arts checkmatearts.com jimstoys.com
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