NSE Labs Projects
The coffee roaster has been rewired with all the previous electronics moved out. The electronics will be mounted in a separate enclosure in this revised design. The new controls are based on a board set called the Atomic Pi, which includes an x86 based processor running Linux, and mounting provisions for an Arduino Nano. The Nano will handle the low-level hardware interface and the Atomic Pi will run Node Red to provide the user interface and remote networking capability.
After messing around with the configuration of the hotspot, and some experimentation with the code plug in the radio, the hotspot is now active.
It works well. I’m able to walk throughout the house and even took the radio out to the mailbox and it worked fine.
The hotspot is on the Brandmeister network and here’s some traffic on the Worldwide talk group (91).
I recently purchased a handheld DMR radio (TYT MD-2017) at a local hamfest and soon found that I can only reach one local DMR repeater from home. But everyone can have their own repeater at home with a DMR hotspot.
I purchased a DMR hotspot kit from eBay (link) and here’s what came with the kit. Note that it does not include the necessary Raspberry Pi Zero W, memory card, and power supply. Luckily I already had those parts on hand.
It also came with these instructions.
The instructions have useful information for setting up the software, but no instructions for putting together the hardware. Luckily it is all pretty straightforward except where to mount the display. There are many places where the four pins of the display could be inserted. I watched a few YouTube videos of similar kits and boards and from that surmised that it should go in the upper header pin row in the farthest left position possible, as viewed from the component side of the board.
The display needs to be parallel to circuit board so I folded a spare antistatic bag to create the right spacing.
Then I placed a weight (my “extra hands” tool) on top of the board to hold it while soldering.
Here’s how it turned out.
Then I soldered the antenna connector on and here is the completed board.
My Raspberry Pi Zero W had the full set of header pins already installed. Note that if you leave the display pins long they will collide with the header pins on the Pi.
If you use the header pins that come with the kit you won’t have this problem. But it is easy enough to trim the display pins which solves the problem.
Now its time to mount the Pi Zero W in the case using the two short screws as shown.
Then add the top board, spacers, and fasten with the two longer screws.
Then put the cover on and add the antenna, that’s it for hardware assembly.
Now its time to download the software for the Pi. I went to this link to download the Pi-Star image. The file I downloaded was Pi-Star_RPi_V4.1.5_30-Oct-2021.zip
I then unzipped the file and used the Raspberry Pi Imager to burn it to a micro SD card. (Click on Choose OS and scroll down to “Use custom”, then select the Pi-Star image).
I next set up this image file with my WiFi credentials by going to the Pi-Star WiFi Builder and filling in the information. It creates a “wpa_supplicant.conf” file that you can copy to the “Boot” volume of the micro SD card that was just created. That way when the Pi boots up it will set the WiFi credentials and connect to the WiFi network.
Then I inserted the micro SD card into the Pi and powered it up. I allowed a few minutes for the Pi to boot and then looked for the IP address of the Pi-Star on my network router. It took several minutes for it to show up – the Pi Zero is definitely not a supercomputer.
Note that the display on the hotspot is blank at this point. We’ll get that working soon.
Once I found the IP address I pointed my browser to that IP address and got this screen.
Eventually it asked me to log in. The username is pi-star and the password is raspberry.
That leads to the full configuration screen.
This is where those instructions that came with the kit finally come into play.
The first thing is to just click on “Apply Changes” – even though we haven’t made any changes yet! This resets the Pi so it takes a while, but then it will come back with new options visible.
Then set the Radio/Modem Type to “STM32-DVM/MMDVM_HS – Raspberry Pi Hat (GPIO)”
The instructions say to set the Display Type to OLED but there are two OLED choices – Type 3 and Type 6. Both seem to display a text message when booting up or shutting down so its not clear which setting is the correct one.
Much more work to do to figure out all these configuration settings, and to get my radio set up to talk to the hotspot.
Eleven years ago we developed electronic digital controls for this coffee roaster. You can view that project summary here. Now it’s time to rethink our coffee roaster controls design based on what’s available today. Stay tuned!