KbxBinaryClock.v2.1

kbx's RGB Binary Clock

RGB Binary Clock project files - PCB and source

It's probably more than what you're thinking...

Another binary clock? Why?

I have to start by giving credit where credit is due. The Boldport Club, over the last couple of years, has motivated me to dwell back into the world of electronics, at least as a hobbyist. Both the kits themselves and the other members in the club are amazing and helped inspire me to make something...so I began working on this project. Some inspiration is taken from Touchy, BPC Project #7; this kit enabled me to learn more about and actually experiment with capacitive touch. It was clear early on that this would be a nice touch (pun intended) to add to this project; visually, it is cleaner, it reduces the number of parts and, as a result, it reduces the cost.

That said, the world probably doesn't need another (binary) clock. There are plenty of them--all different shapes and sizes--so why build another one?

This project was started with two main goals in mind: I wanted a "simple" project I could use to help me get back into the world of electronics. The second goal I had in mind was to build up my comfort level with C and C++ -- I knew the language(s) but was never terribly comfortable with them. Building this helped me to achieve both of those goals and then some -- and I am quite happy with the result!

But why a clock?

It's fun to make LEDs blink. It's fun to play with microcontrollers. It's fun to build stuff. But a blinking LED or two or three isn't very meaningful. Nor is a nice microcontroller that just toggles a GPIO pin. If you're going to build something, why not make it at least modestly useful? And why not build it in a unique way that's neat to look at and/or watch?

The idea for this came from an old electronics kit I put together probably around twenty or so years ago (and it still works today!). I liked the kit but it was somehow lacking. Probably the most obvious problem was that, in a dark bedroom, the display was too bright. It was a simple, 12-hour-only binary clock, built on 4000-series CMOS logic. Now, there's nothing wrong with that, but...it's 2018 now. Let's take it up a notch or ten.

How do you take a binary clock up a notch (or ten)?

First, you can add some color. A lot of color. In fact, you can pick the colors you want it to use...up to eight times over. This binary clock has the ability to gradually shift colors over the course of each day. Bits can even fade in and out as they change. It's all about the eye candy in this regard.

Second, it can do more than just tell the time -- it'll tell you the date and temperature, too! There is even a timer/counter mode. What's more, you can choose the format for it all: the clock can display in a 12 or 24 hour format, the temperature can display in degrees Celsius or degrees Fahrenheit, and (most importantly) it can display all of these values in either binary-coded decimal (BCD) or good old-fashioned binary. You get to choose the formats you prefer and they can be changed easily at any time.

Next, the display brightness issue had to be addressed -- it has a phototransistor which is used to determine the amount of ambient light around it and the display will dim as the light level around it diminishes. This is great if you want to keep it near you at night while you sleep.

Another cool bit is that it uses capacitive sense touch keys for buttons; the kit it is based on had mechanical, fixed-function buttons. If you haven't seen or used capsense technology before, you'll find it's pretty cool and adds a little extra uniqueness to the clock, too.

A CR2032 coin-cell battery back-up can be installed to keep the time valid in the event that the board loses power. Version 4 of the hardware also includes a super capacitor, eliminating the need for the battery; even so, both can be installed, adding flexibility to the build.

Finally--and one could argue that no clock is complete without one--it has an alarm! The alarm can be set to beep at any of the eight times the user sets. There is also an hourly chime that one can enable which will beep out each hour in binary using high and/or low pitch tones...so you can hear the time when you're in another room! The display can be configured to blink when an alarm occurs. Version 4 of the clock also includes extra pin headers, some pins of which can be used as inputs to trigger the alarm from an external device.

Great, but what makes it tick?

The "brain" is an STM32F072 microcontroller. This MCU alone has everything that's necessary to have a functional time clock -- even a temperature sensor as a bonus. Still, it might not be quite as accurate as some of us would like. For those folks, there are footprints for some additional ICs to improve the accuracy of the time and/or temperature sensing.

Version 2 boards have footprints for I2C devices:

• A Maxim DS3231
• An LM75 (or compatible)
• A Microchip MCP9808

Version 3+ boards have footprints for SPI devices:

• A Maxim DS3234
• An LM74
• A Maxim DS1722

Why footprints for both temperature sensors and the RTCs? The DS323x is somewhat expensive and it's possible that one might want more accurate temperature sensing abilities but isn't as concerned with the accuracy of the clock. It should be noted that the DS323x devices have temperature sensors built in and the application will use this sensor if a DS323x is installed but one of the other external temperature sensors is not.

Beyond the MCU itself, the board has 25 RGB LEDs on it; 24 of them form the main display and they are connected to TLC5947 (pre-v4) or TLC5951 (v4+) constant-current PWM drivers. The MCU uses its SPI1 to communicate with these drivers. The remaining RGB LED is used as a "status" LED and it is connected (through FET drivers) to GPIO pins on the MCU. These pins double as timer output channels, meaning they can also generate a PWM signal, enabling the dimming of the status LED elements, as well.

The beeper is connected (also through a FET driver) to yet another GPIO pin that doubles as a timer output channel; this enables the beeper to generate a wide range of tones or even play a tune!

The phototransistor is connected to the MCU's ADC channel zero.

Two USARTs are exposed via pin headers on the right side of the board: USART1 is brought out on a standard six pin header as is commonly found on many devices while USART2 is connected to an RS-485 line driver enabling communication on an RS-485 bus. Through this interface, the application is able to receive a DMX-512 signal so the LEDs can each be individually controlled from an entertainment lighting console (or other application that speaks this protocol), enabling another whole realm of possibilities...

How do I get or build one?

In this repository you'll find everything needed to put one together. It is divided into two major parts: hardware and software (source). The hardware directory contains the KiCad project files used to create the printed circuit board. The src directory contains the source code needed to compile and run the application on the microcontroller. It is built on top of libopencm3. Finally, then bin directory contains compiled binary files you may flash directly onto the microcontroller...great for folks who want to solder something together but don't want to be bothered with compiling code!

Additional details regarding the hardware and software can be found in the README.md files located in each respective directory.

That's all for now...thanks for visiting!