Not everyone wants to use a website or a smartphone to view their data. Some just want a simple wall display.
Eink is power efficient and extremely elegant solution to this problem. It also just so happens that displays are reasonably priced, low-power and they look pretty slick.
We opted for the Pervasive Display range, starting with the original kit using the 1.44″ display and a TI MSP430 G2553. We quickly switched this out for a MSP430 FR5739 and then a MSP430 FR6989. The beauty of the TI MSP430 range is that it is reasonably straightforward to move between MCU’s if you need more features.
We also used the TrxEB to evaluate the CC1120 function. For BLE the microchip RN4020. Each radio having a different use case in mind.
So what were we trying to achieve? Basically a low power elegant display with multiple communication options dependent on range and use case.
The image of our initial demonstrator below shows how we used a FR5739 to act as a CC1120 remote sending data to the FR6989 which runs the display. This used the RN4020 to stream debug into to the Microchip MDLP iOS app.
Although XBee is not demonstrated we have used it extensively in the past and know it will be suitable for the system.
For our final demonstrator we went with the 2.7″ PiPaRus, mainly for the neat form factor. This would give us good visible numbers as well as just looking good.
To connect the FR6989 the PiPaRus should be configured as shown below.
The pin mapping is as follows. Note the red VCC and black GND connections to the PiPaRus.
The PICTail connections are shown below
|Green||UART TX (out from RN4020)|
|Blue||SWAKE, set high to put device into active mode.|
The hardware is essentially the same as our initial system. Most changes were in the software to deal with the message manipulation and the BLE addition to the remote.
For the remote, we use the RN4020 and a FR5739. Readings are generated by a PERL script running on a PC and sent over the USB UART to the FR5739. The program on the MSP430 converts them to integers from the ASCII string, then into a HEX string command for the RN4020. A custom characteristic is used to transmit the data to the display side RN4020.
On the display side we can now see the PiPaRus and the 2.71″ Eink display. A basic layout is used to demonstrate the readings being passed from the remote to the display. These readings are sent with a time stamp which is also displayed. As you can see its pretty windy indoors!
A video of the working system can be seen here. Next step, put it all on one PCB and make a nice bezel!
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