Send for the FireBeetle

If you hit a really nasty problem when you are building something, a good way to attack it is to try to change the problem to one that you think will be easier to solve. You can’t always do this; some customers really want particular deliverables. However, you should never make the mistake of assuming that things that are important to you are also important to the customer. In my earlier days I spent ages getting something to work which was dismissed as “..not really something that we want thanks”. If I’d asked the question “How much to you need this?” earlier I’d have saved myself a lot of effort.

In the case of my environmental sensor I’ve had a chat with the “customer” and discovered that the first set of sensors that are required for testing can be WiFi connected. That means that I can put the Heltec Cube back in its box for a while and switch my attention to something that works over WiFi. I’ve had a play with the DFRobot FireBeetle in the past and so I’ve built a sensor that uses that. The FireBeetle has some nice design tweaks that reduce sleep power consumption. It was fairly simple to port over the software I’ve already written, and I’ve designed a little carrier board that takes the Plantronics PMS5003 sensor along with a FireBeetle and a BME280. And it all works.

The only snag is that I’ve discovered that some device specifications have a lot in common with the current political situation. They are full of things that aren’t true when you test them. The FireBeetle consumes a thrifty 1.5 milliamps when asleep, which is just about viable for our application. Unfortunately the Plantronics PMS5003 sensor, specially selected for its low power features, consumes 4.5ma when I turn off the enable signal. This is much, much more than the amount claimed on the data sheet. Oh well. It turns out that to find out how hard it is to build something you have to build something….