New & Reviewed

New to our Desk: Things On Edge ‘Cricket’ WiFi Module

Daniel Koch

Issue 43, February 2021

A WiFi-connected interface which is so versatile, it’s hard to put it in a category.

We’ve all seen fancy products from start-up companies which promise the world, and we’ve seen them come and go. ThingsOnEdge (TOE), however, isn’t making so much noise about itself. They’re letting their innovative product do its own talking.


The Cricket is a small-footprint, ultra-low-power communication device that has three I/O lines, one of which has an Analog to Digital Converter (ADC) built in, for communication to connected devices. It is intended as an Internet of Things (IoT) tool for developers, makers, and professional users alike. It needs no programming or coding per se, and can connect to a web interface out of the box. It can be powered from a single 1.5V battery, so even one AAA could power it. This makes the overall package very small indeed.


When we say small, we mean that the whole device measures 37.6 x 16.8 x 4mm. It is based around the ESP8266EX and has an onboard antenna giving a range of 100 metres, operating on 802.11 b/g/n WPA / WPA2 standards. There is also an internal Real Time Clock, which is used for scheduled wake-ups among other things. This means that in a loss-of-power event, should the power source not be batteries, the schedule is unaffected. The power source for the RTC is not stated (there is no replaceable on-board battery) but we imagine it is a capacitor. The whole thing is built on a plated and solder-masked PCB with a metal shield over the electronics.


Power supply is from 3.5V down to 1V, and inputs are from 1 to 3.7V for a high, with anything below 1V seen as a low. There is an onboard regulator which gives a constant 3.3V output for powering sensors, down to a battery voltage of 1V. The ADC is curiously scaled to 3.7V rather than 3.3, so sensors with 3.3V outputs will have to be corrected in software. Battery options are listed in the Developer Guide, which clearly states that anything over 3.5V will need a DC-DC converter. While this rules out 3.7V lithium batteries, all design decisions are an exercise in trade-offs. This trade-off means that small, long-life disposable batteries can be used. Even LR44 or CR series batteries will work. This raises the possibility of genuinely wearable sensors. In deep sleep, the device draws half a microampere. Yes, that’s 0.5μA.


While there are three I/O lines, one is dedicated to wake-up signals. One is a purely digital I/O, while the other is either digital or ADC. As noted, the full scale for the ADC is based on 3.7V, which translates as 0 - 255. The TOE Cricket also has an internal temperature sensor, and the developers have also constructed a web interface that you can use. That, in combination with its lack of need for programming, means you can unpack it from new, connect a battery, and connect it straight to your WiFi. As soon as you configure the settings, it starts working. You can get the temperature data straight away, so not only can you test and experiment with settings, but as-is, the Cricket makes a great remote temperature sensor.


Physical connections to the Cricket are by solder pads with plated-through holes at one end of the board. They’re labelled on the underside, which makes life easier. In terms of interfacing digital connections, the Cricket can be set up to provide its data through HTTP or MQTT. The latter is fast becoming the standard in IoT systems but the TOE team have done well by including both protocols, as it adds diversity to the product. It can potentially integrate into pre-IoT systems such as older IP data monitors operating on fixed wiring. If you’re not familiar with either, there is a MQTT free broker (the term for the software-driven system that processes data from IoT devices and displays it on a web page). It is the one used to make initial configurations and it turns out to be fairly easy to use.


On the subject of knowing what goes where, there are several documents provided online for the Cricket. One is a quick-start guide in the form of a Google Slides presentation. This covers the basics like power connection, but also shows you how to configure the settings and connect to web interfaces. There is an untitled single-page quick-reference guide as well, which uses both text and images to convey the basics, This feels more like a reference for someone who has already used the Cricket but not enough to memorise everything - it assumes some familiarity. Finally, there is a Developer Guide, which is one long web document but if printed, would be 41 pages. This guide contains all the relevant information, dozens of links, and three complete examples of working projects, using different aspects and interfaces.


To test the Cricket sample we were given, we used the Quick-Start guide. Following it directly, we soldered on a 2AA battery pack, installed the batteries, and held down the tiny button for the stated five seconds. There is a small blue LED which turns on continuously while the button is down (so you know if you’re not pushing correctly), then starts flashing once it is in connection mode. We had to refresh our phone’s connection page, then the TOE_Device showed up immediately. If you don’t connect within around two and a half minutes, the device goes back to sleep.

After this, we opened a browser, entered the provided IP address, and were taken straight to the configuration page to connect to the building WiFi. With our details entered, we were able to view the data in the ‘Info’ tab, which gave a range of data including WiFi signal strength. Next is the ‘Config’ panel, where we named our device DIYCricket. We also enabled the onboard temperature sensor, and the battery monitor function. You can set the resolution of the latter from 1 bit to 8 bits, giving a 0-255 scale for the battery voltage. Save yourself some time and write down the serial number from the ‘Info’ panel. After this, the ‘reset’ button on the interface (not the Cricket) is pressed, which sends the data and disconnects the phone. The Cricket is now connected to the WiFi.

Although not shown in the Quick Start Guide, the MQTT interface used is a Chrome Plug-in. The Cricket will work with any MQTT interface, but if you’re just learning about MQTT, then following the Quick Start Guide letter-for-letter makes sense. We downloaded and added the app for Google Chrome, and opened it. It opens in a separate window, being an app rather than an extension to the browser. After filling in the details, we discovered that the connection requires the serial number from the ‘Info’ panel from the direct connection. That’s why we mentioned above to write this down. We didn’t know, and had to repeat the connection procedure to get the data. The serial number is entered in both the ‘serial number’ and ‘password’ fields. By the way, the Developer Guide has much more detail but we didn’t have the time to read it cover to cover at 41 pages, and still fit into the production schedule. If you’re using the device seriously, then this document is worth reading all the way through.

Immediately, we hit problems. More specifically, we hit a firewall, and it was our own. The way the office WiFi is set up is very secure, and it doesn’t like anything it hasn’t been told about in several different places. The complications were situation-specific, and not Cricket-related. It’s worth noting this if you’ll be using yours in a similar environment. We also had problems with the Windows firewall, but these were also resolved. The one problem we did find in the documentation at this point, was that the subscription topics are labelled in the document as /SERIAL/temp, or whatever parameter. It isn’t clear if you’re not familiar with MQTT, but that is not serial as in serial data. You actually need the serial number of the device in that place, replacing the letters of the word SERIAL. Now we had battery and temperature data popping up at the interval we had set, and it kept doing so overnight and across the next few days with no hang-ups.

Of course, the Cricket from ThingsOnEdge is far more versatile and capable than this, and can be connected to an array of sensors or data inputs. The presence of an ADC means 3.3V sensors can be connected directly without the need for another micro to handle the data conversion. The Cricket suits genuine remote monitoring situations, and so we would like to see a version which can accept an external antenna, for kilometers rather than metres of range.

We would also like to see an upper voltage limit closer to 4V, to make use of 3.7V lithium batteries. Both of these factors would make the Cricket bigger, however, and so these features would be best served in a separate version. Things On Edge also advise that they have tested the Cricket with 4V and done no damage, but calculated limits are 3.5V. As it is right now, we’re confident that anyone who is involved in, or wants to learn about, sending wireless data to web-based hosts, will find the Cricket very appealing.

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The IOT Cricket - Wi-Fi module is available from ThingsOnEdge: