Tiercel
The dial that leaves the wall. A round touchscreen inside a knob you turn, with a battery, a microphone and a headphone jack. Take it to the campfire and ask your rig how it is doing.
What's Inside / Display
The Knob That Travels
Most of the time it sits in its spot like any other control. When you head outside, it comes with you. Tap the screen, ask a question, and the answer plays through your headphones and shows up on the screen.
Tiercel runs on one off-the-shelf board, the Waveshare ESP32-S3 Knob: a 1.8-inch round touchscreen in a CNC aluminium case, a knob that turns on a bearing, and a haptic motor that clicks under your thumb. It joins your rig's own WiFi and talks to Headwaters, so there is no cable to run and nothing to solder.
The Waveshare link carries our affiliate tag. It costs you nothing extra and sends a small cut back to the project.
Tiercel or Capstan?
Both. They do different jobs, the same way Milepost and Fireside do.
Capstan stays put
A small dial you place by the door, the bed or the galley. Turn, press, hold. Touch is switched off, so it works by feel, with gloves on, and nothing happens when you brush past it. Three sizes, and the smaller two have a ring of light.
Meet Capstan →Tiercel goes with you
Runs on its own battery, so it leaves its spot when you do. It listens and talks back, so you can ask the rig a question and hear the answer. You turn the knob to move and tap the screen to choose. There is no press, so bare hands work best.
Hear it answer ↓Take It Outside
A control that only works where it is mounted is a control you walk back to. This one comes along.
By the fire
Check the battery, switch off the awning light, or ask how much water is left, without getting out of the chair.
At the tongue
Pulling into a site? Carry it to the front of the trailer and watch the level reading while you set the blocks. No walking back inside to check.
Back in its spot
When you are done, it goes back where it lives and charges over USB-C. It stays connected as long as it can reach the rig's WiFi.
Ask the Rig
Tap the screen and say what you need. "How am I doing on power?" "Turn off all the lights." Tiercel hears you, and Peregrine, the rig's own AI assistant, answers out loud and on the screen.
Peregrine runs on your hardware, in your rig. Your question never leaves your network, and it works at camp with no signal. One tap starts it. You do not hold anything down, it knows when you have finished speaking.
There is no "Hey Peregrine" on the dial yet. A wake word needs a model the chip can run, and that work is still ahead. For now it is one tap.
Headphones or speaker
Replies play through the 3.5 mm jack, or pair your Bluetooth headphones in Settings and they reconnect on their own after that.
Volume on the knob
Turn to make it louder or quieter. At the top or bottom the knob bumps back, so you feel the limit without looking.
Read it, too
What it heard and what it said stay on the screen, so a noisy campsite does not mean a missed answer.
The Whole Rig, in Your Hand
Everything Capstan shows, Tiercel shows too. Turn to find it, tap to choose.
Devices
The lights and switches you give this dial in Overlook. Turn to pick one, tap to switch it.
Energy
Battery, solar coming in, and what the rig is using, with time remaining.
Water and Leveling
Tank levels and whether the rig is sitting level, from anywhere around the site.
Air Quality
The readings from Borealis, at a glance.
Alerts
A door opens while you are driving, and the screen takes over with a buzz you feel until you tap it.
Clock
Leave it alone and it turns into one of four clock faces.
One Board, Straight From the Vendor
No custom PCB, and no soldering for the dial itself.
| Board | Waveshare ESP32-S3-Knob-Touch-LCD-1.8 |
| Screen | 1.8", 360×360 round, capacitive touch |
| Input | Knob with detents (turns, does not press), touch, haptic motor |
| Audio | Microphone, 3.5 mm headphone jack, Bluetooth headphones |
| Power | USB-C, plus an 800 mAh battery that charges on board |
Pick the standard version (blue, or black as the 1.8B), which ships with the battery fitted. The versions ending in -EN come without one.
Under the Hood
Two chips share the case. An ESP32-S3 runs the screen, knob, WiFi, microphone and audio. A second ESP32 handles Bluetooth headphones, which the S3 cannot do by itself. The firmware is ESP-IDF with LVGL 9, and both chips flash through the same USB-C port: plug it in one way for one chip, flip it for the other.
Designed in EEZ Studio
Every screen is laid out in EEZ Studio, so you can see a change on your computer before it ever reaches the dial. The project file is in the repository alongside the firmware.
Powered by EEZ Studio
Build One
One board and a USB-C cable.
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1
Get the board
The Waveshare ESP32-S3 Knob, in a version with the battery if you want to take it outside.
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2
Back up the factory firmware
Save what is on both chips before you flash anything. The repo shows how.
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3
Build and flash
Build with ESP-IDF and flash over USB-C. Flash the second chip too if you want Bluetooth headphones. The build guide walks through both.
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4
Connect it from your phone
On first boot the dial creates its own WiFi network. Join it from your phone, enter your rig's WiFi and the details for Headwaters, and it restarts connected. No app, no internet needed.
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5
Give it a job
Headwaters finds the dial and hands it its devices, its alarms and the way to reach Peregrine. Nothing else to type in on the dial.
The dial needs no soldering. The rest of a TrailCurrent system does need some wire-to-wire soldering, so plan for that when you add your next module.
Questions
The ones people ask first.
How is Tiercel different from Capstan?
Capstan is a turn-and-press dial that stays where you put it. Tiercel runs on a battery, so it comes with you, and it has a microphone and audio out, so you can talk to Peregrine, the rig's own AI assistant, and hear the answer. Tiercel has no push to select: you turn the knob and tap the screen. Most rigs will want both.
Does the board come with a battery?
The standard ESP32-S3-Knob-Touch-LCD-1.8 and 1.8B ship with an 800 mAh battery already fitted, and the board charges it over USB-C. The variants ending in -EN come without a battery. Pick one with the battery if you want to take it off the wall.
Does the voice assistant need the internet?
No. Tiercel talks to Peregrine, which runs on your own hardware in the rig. Your question and the answer stay on your network. If you would rather point Peregrine at a bigger model you already run, the replies come back faster.
Can I use it with gloves on?
Not well. The knob turns but does not press, so every selection is a tap on the screen. If gloves are part of the job, Capstan is the better dial for that spot.
Does it say "Hey Peregrine"?
Not yet. Tiercel is tap to talk: one tap, say what you need, and it listens until you stop. You do not hold anything down. A wake word needs a model the chip can run, and that work is still ahead.
Can Tiercel control my RV thermostat?
Not yet. The Climate screen shows the live inside temperature, and the setpoint is built into the interface, but TrailCurrent's thermostat control that it will drive does not exist yet. Everything else on the dial works with modules that exist now.
Is Tiercel free and open source?
Yes. The firmware, the EEZ Studio project and the documentation are MIT licensed on GitHub, like every TrailCurrent project. No subscription, no paid tier.
Take the Rig With You
Firmware, the EEZ Studio project, and the board notes are all in the repository. The announcement post tells the story behind it.