Weather calendar: Pyboard

I found it very easy to get the Pervasive Displays e-ink working with the Pyboard once I discovered Peter Hinch’s github library. This not only made the display access easy but also helped with forming the fonts and digits.

img_20160926_151226

The components I used were:

  • LiPo battery, supplies 3.3V and my one is 850maH.
  • small plastic container
  • battery charger from Adafruit
  • Pyboard
  • RTC battery backup in the form of a CR2032 battery.

I also used another of Peter Hinch’s libraries to determine the ‘drift’ of my Real-Time clock on the board I have, and came out with a calibration of -145. Yours may be different, run the tests!

The code was simplicity as once I had set the RTC using the ‘finger’ method of waiting until the seconds changed on my desktop system and sending the command (this is bound to be perhaps 0.5sec wrong, but who cares?) then the battery backup along with the calibration setting should keep it reasonably accurate.

The problems were a couple: the blue light on the battery charger “was very bright” and kept my son awake at night in his room where we tested this clock, and the battery ran out after just a few days. For those who say ‘get a bigger battery’, I actually don’t care what size as the system I want to build should be able to run on a coin battery if needed – I really don’t want to recharge things constantly nor have a large lead-acid car battery sitting under my display.

Code was simplicity itself with just a few lines:

# MicroPython to display digital clock on Embedded Artists e-ink display
# Using epaper library from Peter Hinch
#
# (c) Doug Hall 2016

import time

import epaper

import pyb

a = epaper.Display('L', use_flash=True)
t = time.localtime()
rtc = pyb.RTC()

a.clear_screen()
with a.font('/fc/nunito64x68'):
 a.locate(50, 50)
 a.puts('{:d}:{:02d} '.format(t[3], t[4]))
 a.show()

rtc.wakeup(55000)
pyb.standby()

All in all a good first attempt at writing Python, using an embedded system, and getting an e-ink display running. Downsides were the Pyboard battery consumption, the Pervasive Display itself was a little small (and I ‘cooked’ one with wrong voltage!), and the large ribbon cable connections seemed unwieldy.

On to the next attempt…

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