Table of Contents
Adding a new sensor
A step-by-step walkthrough for adding a sensor that Axiom doesn't recognise. You find it on the bus, add a profile from the catalogue, install it and check that Axiom now claims the device.
This example adds an AHT20 temperature and humidity sensor at I²C address 0x38. The AHT20 is in the catalogue but isn't built into the current Device Library firmware. The same steps work for any sensor that has a catalogue profile. If yours doesn't, see Writing device profiles.
Before you start, work through Getting started so your Axiom has Device Library firmware.
Connect the sensor
- Switch Axiom off before connecting or disconnecting a sensor.
- Connect the sensor, then switch Axiom on and plug it into your computer over USB.
- Open the Device Library and click Connect Axiom via USB.
It helps to know your sensor's I²C address. You can find it in the sensor's datasheet or in the Addr column of the Catalogue.
Scan the bus
Open the Test & tune tab and click Scan bus. The table lists every address Axiom found:
- claimed: a profile recognised the device. The Resolved type column shows which one, and Origin says whether it is built-in or yours.
- unclaimed: something answered at this address, but no profile recognised it. Your new sensor should appear here, e.g. 0x38 … unclaimed … nothing claimed this address.
- direct rows are Axiom's own internal devices, such as its LEDs and power system. They aren't on the I²C bus.
If your sensor's address isn't in the list at all, Axiom can't see it. Check the wiring and the address before going further. See Troubleshooting.
Add a profile to your draft
Click Find catalogue candidates. For each unclaimed address, the Device Library lists catalogue profiles that use that address. For 0x38 it suggests AHT20:
- Try AHT20 asks the device the profile's identification question, if the profile has one. It talks to the real device but installs nothing.
- Add AHT20 to draft copies the profile into your draft.
Many different chips use the same I²C address. A candidate means “this profile uses this address”, not “this is your device”. Check the part number on your sensor.
You can also add profiles from the Catalogue tab. Search by name, maker, class or address, then click Add to draft:
Either way, the page confirms AHT20 added to your draft. Nothing has been sent to Axiom yet.
Review and write to Axiom
Open the Install tab.
- What will change compares your draft with the library file on Axiom. Here there is one change: add AHT20: new type at 0x38 — nothing built in claims it. The footer shows how much of Axiom's library space the draft uses.
- The write shows the file that will be written, its size, and what Axiom will have afterwards.
Tick I have reviewed what will be written and am ready to restart Axiom, then click Write to Axiom. The page confirms Written to Axiom. Restart it to start using this library.
Write to Axiom replaces the entire library file with your draft. Anything on Axiom that isn't in your draft is removed. If Axiom already has a library you want to keep, first click Use Axiom's library as draft on the Install tab, then add your new profile.
Restart Axiom
Writing doesn't change the profiles Axiom is using yet. Click Restart Axiom. The page waits for Axiom to restart and then reads its state again.
If USB stops responding after the restart, unplug Axiom and plug it back in, click Connect Axiom via USB and then Refresh device.
Check the result
The status strip should now show In use · 1 added · 0 disabled. On the Install tab, What Axiom did with the file it has shows what Axiom made of the library when it started:
- added counts the profiles Axiom accepted.
- disabled counts the device types you switched off.
- rejected counts the entries Axiom refused. If it isn't 0, the page shows the first error. Fix that entry in your draft and write again.
Finally, go back to Test & tune and click Scan bus. The sensor's address should now be claimed by your profile, with origin yours. After a restart, Axiom can take up to a minute to finish finding its devices, so if the address still shows as unclaimed, wait a little and scan again:
Click Start readings to see the latest values from each device. Click Stop readings when you've finished. See Testing and tuning devices for more.
A claimed address means a profile matched the device, not that every reading is right. Compare a few readings with what you expect (e.g. room temperature) before relying on a new profile.
Next: Customising and disabling built-in devices.