This project is about an OLED Wrist watch built around 16-bit controller known by the name MSP430 and is manufactured by Texas Instruments. These controllers are designed specifically for low-power or battery powered operations and seems to be a perfect choice for a wrist watch. It runs on a cr2016 based coin cell and an OLED display. This project is actually an update to the older edition since the author wanted to enhance its battery life. Earlier it used to consume around 3ma of current but now it’s capable of consuming current in micro amperes with a good OLED display.
The watch also has an on-board accelerometer in the design, which is used to detect tap and double tap so that it can wake up the controller using interrupts. The accelerometer has a shared SPI bus with the display. Also an under-voltage circuit has also been placed so that it can be used with an unprotected LiPo. The controller used is MSP430FR5738 which is a part of the MSP430 family and consume a way less current. Another advantage is that it has a Ferroelectric RAM which is also capable of zero-power data retention.
The MSP430 is a famous series of 16-bit controllers from Texas Instruments. They are mainly used for battery-powered and low-cost based projects. The article aims at interfacing a popular series for DAC named as DAC7564, which is also manufactured by Texas Instruments as well as other semiconductor corporations. The DAC7564 is a low-power, voltage-output, and four-channel, 12-bit digital-to-analog converter (DAC). The device includes a 2.5V, 2ppm/°C internal reference. The device is monotonic, provides very good linearity, and minimizes undesired code-to-code transient voltages (glitch).
An N-bit string DAC simply consists of 2N equal resistors in series and 2N switches (usually CMOS), one between each node of the chain and the output. The output is taken from the appropriate tap by closing just one of the switches. An MSP430 is used to send the data and the SPI communication is done by bit-banging. A library provides functions to send, receive and transfer data using SPI protocol. Being a bit-bang communication there is no particular hardware module necessary and any MSP430 would work, in this particular case a MSP430F2274 is used.
The project also known as Spoke ink creates a beautiful patterns in a shape of an image which is user defined. Spoke Ink is a booster pack for the MSP430 series of microcontroller, which uses 32RGB Led’s along with a magnetic sensor. The image to be displayed on the spoke can be created form any bitmap image by using the software provided by the maker itself. The booster packs creates an image by using persistence of vision which is the same technique used in videos.
2NITo generate a persistent image, Spoke Ink and the MSP430 have to light up in the exact same radial position with each turn of the wheel which is achieved by triggering interrupts based on a small magnetic sensor that trips each time the booster pack passes a small magnet glued to stationary part of the bicycle. The project requires very basic components such as RGB LED’s Hall Effect sensors along with the launch pad for MSP430 and the booster pack mentioned above.
Digital DIY clocks are and will be one of most popular microcontroller projects. And it seems that people never run out of ideas to make it a bit different. Markus built pretty simple digital clock that is driven by MSP430 microcontroller. Two dot matrix LED displays are used to display time and various status information.
Two push buttons allows selecting necessary parameters like time, alarm settings, etc. Some special attention is paid to alarm section. It consists of two components – bright LED and buzzer. As seen from video, at the beginning alarm flashes LED with silent buzzer tick. For some people this is enough to wake up. If this doesn’t work, then alarm starts going crazy with more intense flashing and annoying music played on buzzer. Clock is powered from single LiFePo4 battery which is more than enough to power it for quite long time. Algorithm takes care of saving power with various means starting by turning off LED display after some time.