Revision R2 of MightyHat is now available. Since the changes are not very significant I debated whether this should be really a R1.1 but I don’t like minor revision numbers so I went with R2. Basically it just adds the following main features:
- Battery power switch – this is a slide switch that can cutoff the battery. During my many hours of testing, it occurred it would be useful to just have an onboard battery switch instead of pulling it in and out. Also if you have the battery tucked tight underneath the board it’s not always really easy to pull the JST connector. Or say if you want to ship a complete Pi+MightyHat+Battery inside an enclosure and don’t want to have it powered up. A side switch is convenient for this purpose:
If you don’t want the switch then there is a solder jumper behind it which you will need to solder-bridge if you are using a backup battery.
- Two momentary tactile buttons tied to the remaining available I2C pins which were previously unused (A4 and A5). These will be general purpose buttons to do whatever you like. If you want you can build some menu interaction for the LCD or whatever else. They connect GND to A4 and A5 and the pins should be declared as INPUT_PULLUP. The provided kit buttons have long actuators that rise just above the main power button (to allow pressing them when enclosed), but you could otherwise solder any standard 6mm tactile buttons here.
- A few power path optimizations and tweaks.
- I sourced RP-SMA connectors which seem to be a lot more popular than SMA (shown in photo below – note male pin in the center).
- Besides the new positions/cutouts of the buttons and switch all other physical features remain at the same positions as R1.
I have an enclosure close to finalizing so maybe I will post that when it’s ready for those who’d like to lasercut their own case. I played around with 1/8″ and 1/16″ acrylic and finally settled on 1/8″ because it’s more dimensionally stable and makes for a sturdier case. The thin 1/16″ was light but it was prone to breaking where holes were very close to the edge or between USB/Ethernet connectors. Here are a few snapshots of R2:
Wondering what it takes to put together a kit with all the necessary parts to make a completely functional piece of hardware like this? Consider these facts:
- The PCB board has some 62 SMD parts on it after picking and placing.
- Some 13 more through hole parts (and the SMD transceiver) are required to be sourced and soldered separately (some optional like the LCD, buzzer or SMA connector).
- To make a nice tight fit while avoiding any shorts or touching ontop of the Pi, an optimal height of 17mm is required between the Pi and MightyHat. Standoff combinations were sourced to achieve this height since 17mm is not standard or easy to find stanoff height.
- Add a 1-cell 3.7v Lithium Polymer battery (optional) to act as a UPS and you are golden. I recommend this 2Ah battery from Adafruit which has decent capacity and attaches nicely with velcro under the Hat.
- Total height of the Pi+MightyHat with all options installed is just 32mm (about 40mm when enclosed with 1/8″/3mm acrylic).
Finally I need to mention I have made numerous tweaks and improvements to the RFM69 gateway sample sketch for the MightyHat. I added a bunch of defines that make it easy to disable the LCD, wireless programming, or Automatic Transmission Control. Besides making the sketch a lot smaller (LCD has the largest footprint because of fonts and graphics), it allows running your gateway without an LCD: