A while back, I was trying to set up a power monitoring system, and I mistakenly bought the wrong ESP dev board. The ones I ended up are sold by some fake-named Chinese manufacturer. They seem pretty fine, much like any other ESP32 dev board, but they have an unusual 30-pin layout.

I tried to add some electronics to my whiteboard hack earlier this month, but got frustrated pretty quickly, failing to program the microcontroller, and with no idea what the pinout was.

Today I decided to take it slower. I'd figure out how to program it, and understand the pins. If I had any time left over, I'd do a project.

First, I got flashing the chip to work. It turns out my main problem from the first time was a bad upload serial rate. I debugged the problem with the help of friendly folks on IRC. Espressif (the ESP32 manufacturer) has helpful troubleshooting instructions, which suggest using the python serial terminal, miniterm. By taking a step at a time, I got the microcontroller working.

Next, I installed and set up platformio, which I had never used before. My experience was that it was pretty good once set up, but a little hard to get started on the command line. Still, I'm happy, and will probably use it again. Platformio has two options--the popular Arduino framework libraries, or the Espressif-provided esp-idf libraries. Based on the small code samples I found, I'll most likely use the Arduino libraries, but some specialty features are just not available on Arduino.

Finally, I set up platformio one last time, with the VS-Code based PlatformIO IDE. Again my experience was pretty good. Sadly, the open-source VS-Code does not show the same set of extensions, and I had to use the binary version. (Aside: Come on, vs-code. Don't call your package and program code. That's a dick move.)

The writeup of how to get your dev environment set up is on github.

Finally, I made the below pinout diagram with the rest of my night.

Happy hacking!

A friend of mine, Kragen Javier Sitaker has been designing something he calls the zorzpad (see link below). I can never remember the name, so as a joke my version became the “zorch pad”. We live on opposite sides of the globe, but we’ve picked up the same or similar hardware, and have been having fun developing the hardware and software together.

The basic idea of the Zorchpad is to have one computer, indefinitely. It should keep working until you die. That means no battery that runs out, and no parts that go bad (and of course, no requirements to “phone home” for the latest update via wifi!). This is not your standard computer, and we’ve been trying a lot of experimental things. One of the main requirements is that everything be very low-power. He picked out the excellent apollo3 processor, which theoretically runs at around 1mW. In general, the zorchpad is made of closed-source hardware.

Since I’ve realized this will be a long project, I’m going to post it piece-by-piece as I make progress. Below is a demo of the display.

The graphics demo shows, in order:

• a title screen
• a flashing screen (to show graphics-mode framerate)
• a demo of font rendering. we’re using the fixed-width font tamsyn.
• a munching squares animation
• a demo of how fast “text-mode” updates would be

We’re using a memory-in-pixel LCD. The only manufacturer is Sharp LCD. You have have seen these before in things like the Pebble watch–they’ve very low-power except when you’re updating. This particular screen is quite tiny–240x400px display (which is fine with me), but only 1.39×2.31 inches (35x59mm). The only bigger screen available in this technology is 67x89mm, a bit lower resolution, and out of stock. As soon as it’s in stock I plan to switch to it.

According to the datasheet, the screen consumes 0.05-0.25mW without an update, and perhaps 0.175-0.35mW updating once per second. We haven’t yet measured the real power consumption for any of the components.

The most obvious alternative is e-ink. E-ink has a muuuch slower refresh rate (maybe 1Hz if you hack it), and uses no power when not updating. Unfortunately it uses orders of magnitude more power for an update. Also, you can get much larger e-ink screens. The final zorchpad might have one, both or something else entirely! We’re in an experimentation phase.

Datasheets, a bill of materials, and all source code can be found in my zorchpad repo. Also check out Kragen’s zorzpad repo.

I’m on Linux, and here’s what I did to get the Adafruit Pro Trinket (3.3V version) to work. I think most of this should work for other Adafruit boards as well. I’m on Arch Linux, but other distros will be similar, just find the right paths for everything. Your version of udev may vary on older distros especially.

1. Install the Arduino IDE. If you want to install the adafruit version, be my guest. It should work out of the box, minus the udev rule below. I have multiple microprocessors I want to support, so this wasn’t an option for me.

2. Copy the hardware profiles to your Arduino install. pacman -Ql arduino shows me that I should be installing to /usr/share/aduino.  You can find the files you need at their source (copy the entire folder) or the same thing is packaged inside of the IDE installs.

   cp adafruit-git /usr/share/arduino/adafruit
   

3. Re-configure “ATtiny85” to work with avrdude. On arch, pacman -Ql arduino | grep "avrdude.conf says I should edit /usr/share/arduino/hardware/tools/avr/etc/avrdude.conf. Paste this revised “t85” section into avrdude.conf (credit to the author)

4. Install a udev rule so you can program the Trinket Pro as yourself (and not as root).

   # /etc/udev/rules.d/adafruit-usbtiny.rules
   SUBSYSTEM=="usb", ATTR{product}=="USBtiny", ATTR{idProduct}=="0c9f", ATTRS{idVendor}=="1781", MODE="0660", GROUP="arduino"
   

5. Add yourself as an arduino group user so you can program the device with usermod -G arduino -a <username>. Reload the udev rules and log in again to refresh the groups you’re in. Close and re-open the Arduino IDE if you have it open to refresh the hardware rules.

6. You should be good to go! If you’re having trouble, start by making sure you can see the correct hardware, and that avrdude can recognize and program your device with simple test programs from the command link. The source links have some good specific suggestions.

Sources:
http://www.bacspc.com/2015/07/28/arch-linux-and-trinket/
http://andijcr.github.io/blog/2014/07/31/notes-on-trinket-on-ubuntu-14.04/