Weather calendar, part deux!

Whilst some of my systems have worked, some have not. First up, I have no problem in getting a display on the e-ink displays which I have (a Pervasive Displays, Waveshare) using their demo programs and using either a USB connection or an Arduino.

Arduino

Simplest is the Arduino code and communicating to this via a USB connection, using the Arduino GUI on a Linux machine. This works!

PC

Second easiest is talking to the display directly using a UART connection from a PC, such as the CP2102 chip and driving the display via the USB cable:

  • Using a Python library works well.
  • Using the C code supplied by Waveshare themselves as a library – not tried but I assume it would work like the Python code.

Adafruit Feather Huzzah

  • running MicroPython did not work and gave a memory error
  • running the NodeMCU?

Eventually the memory error helped realised that I may have been approaching it like it was a large system, is there a way I can keep the memory requirements much lower and get the display working? The Huzzah is a good system, although it is a little power-hungry for my liking.

WiPy

Using a WiPy running MicroPython also did not work. I was a little disappointed with this as I think the system is a good one.

Photon

I’ve one of the little Particle.io systems and have played with it, but as the programming was not in Python not taken it further. It could be a possibility but I want to push the MicroPython boards to see if one can handle what I want to accomplish.

Pyboard

I have one of the v1.0 Pyboards from the Kickstarter campaign, and got this working driving the Pervasive Displays display. Mostly because someone else wrote the code and gave a great walkthrough for the wiring and soldering needed.

ESP8266

I’ve ordered a ‘raw’ ESP8266 as one Youtube video shows that working okay as an endpoint, with the Python code running on a backend laptop. I can get one of my small SBCs to do the driving. More on this later…

TXB0108

Logic voltages have changed over the years since the Arduino first came out, and modern chips are largely based around the 3.3V compared with the 5V of the early Arduino systems. Of course this varies and some are 1.8V and so on. I wondered if I were driving the display with the wrong voltage. The Waveshare site claims that the display can handle 3.3-5V okay, although I note that they say you feed it 5V when using their demo program to talk to a PC.

I tried to use a level shifting chip – the TXB0108 – which will either up-shift or down-shift the logic levels on the control lines (and not the voltage! – that I had to realise, so you still must supply 5V somehow). Whilst the results were tantalising, they were inconsistent when only supplying 3.3V to the display as often the updates would not come through and the screen looked ‘broken’.  Feeding 5V worked perfectly. Learning about level-shifting was fun, and may come in handy for later projects, but I’ve assumed that I need a 5v feed to the Waveshare display with 3.3V logic levels on the TX/RX and

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