About 18 months ago, we brought you a sneak peek at a handheld that started life in the Dutch conference badge scene. At the time it showed promise, but its software wasn’t ready for a fair review. Now it has both a stable operating system and a growing software library. It’s time to put it through its paces and see what it can do.A Handheld Computer For HackersThe bare PCB, with the expansion connector bottom centre.The Tanmatsu (Japanese for “Terminal”), is a general putpose palmtop computer based around an ESP32-P4 application processor from Espressif. It takes the form of a PCB and PETG 3D printed sandwich, with the front face PCB sporting a silicone QWERTY keyboard and an 800×480 MIPI DSI display. The keyboard should be familiar to many readers, being the same moulding as the Solder Party KeebDeck which has appeared on other devices.Under the hood that P4 has two 400MHz RISC-V cores and 32MB of PSRAM with 16MB of Flash, and there’s an ESP32-C6 for WiFi, BLE and IEEE 802.15.4 mesh networking. There’s an Ebyte LoRa module with an SMA antenna too, which can be had in 868, or 915MHz versions depending on where in the world you live.For interfacing there are USB A and C ports, and SD card socket, a 3.5 mm jack for audio, and three expansion ports. On the right side a Qwiic compatible socket, on the left a socket with PMOD and SAO capabilities, and on the rear under the cover, a CSI camera connector the same as the Raspberry Pi, and a much larger expansion socket with all the various signals, planned for add-ons. It’s all powered by a chunky 2500 mAh LiPo which can be charged through the USB-C port.Because I know the folks behind it I’ve watched it grow from its origins in a souped-up version of the MCH2022 badge into its current form, indeed I bought my Tanmatsu just over a year ago. Due to those origins in the Dutch badge team, this device is open-source. The Tanmatsu is a commercial version produced and sold by Renze Nicolai, its designer, while the Konsool is its community cousin. You can find its mechanical hardware here, its electronics here, and its firmware here.An App Repository For Your CreationsTurning the Tanmatsu on, after a synthwave-inspired splash screen you find yourself in a graphical menu. The user interface is pretty intuitive to anyone used to a desktop GUI or a modern smartphone, along the top are status icons for SD card, Wi-Fi, and battery, the main body of the screen has a grid of icons, and along the bottom is a list of the various keyboard shortcuts. Navigation is via a set of arrow keys with the return key selecting an option, and a set of coloured function keys handle special functions.Meshcore is only a download from the repository away.On first start-up the Tanmatsu has no apps installed, so the first order of business is to connect to a Wi-Fi network and update the firmware through the Settings. It takes a while to do this as it can update the firmware on the P4, the C6, and the microcontroller it uses for housekeeping. A feature I like is that this is the first device from the world of badges I’ve seen that can hold more than one set of Wi-Fi network details rather than requiring me to change the settings at each location.With a freshly updated Tanmatsu you can open the repository, this device’s app store, and download some apps to get started. This is a long-standing badge.team feature, in that badges going back to their SHA 2017 offering have had downloadable apps. The apps are sorted into categories for easy navigation, and in my case there are immediately two apps I have installed, the Tamatype camera app for my Pi camera add-on, and from the choice of two different Meshcore apps, Wadamesh.The apps themselves come in two forms, either ones written in an interpreted scripting language such as MicroPython, or those compiled directly for the P4. It doesn’t ship with a script engine installed, however MicroPython is downloadable as an app from the repository. This is not a multitasking device so the front-end is a launcher, and after running an app the screen will flash blue for a moment as it loads. Each app has a metadata file which instructs the Tanmatsu what to do with it, an icon file, and a folder containing its executable components. There’s a comprehensive online guide, should you wish to try developing your own apps.In use the Tanmatsu is convenient to hold and type with using two hands. The display is clear and bright, and the keyboard while a little on the small side has a positive click action. Using the apps depends on the individual choices of the app developer, but the interface conventions are straightforward. I’ve been using it for Meshcore for a while now, and it makes a very handy terminal indeed.In A Niche Of Its OwnThe price of a fully assembled Tanmatsu is 99 Euros, plus Dutch sales tax if you live in the EU, and shipping. The good news for Americans in an age of uncertain tariffs is that I’m told they will be shipping from a US warehouse in the next few months. It’s worth considering for a moment where this places the device in the ecosystem of similar computers.It’s relatively simple to make a handheld Linux cyberdeck using a Raspberry Pi board, however once the price of new peripherals and parts is taken into account it’s not necessarily a cheap project. There are quite a few similar-sized Linux devices on the market whose prices reflect this at about twice as much. Thus I think that the Tanmatsu fits in a middle zone between development boards that come without the screen, battery, and keyboard, and those Linux handhelds that are all-singing all-dancing.In its favour it’s as far as I know the only P4 device on the market with a mature operating system and particuarly an app repository, but if only Linux will do, it’s unable to deliver. Where I think its niche lies is in being simple and low power enough to be a reliable and powerful hacker’s communicator and general purpose toolkit, but cheap enough to remain a reasonable purchase. For now it stands alone in that niche, and only time will tell whether it can successfully define it.