Support Acaia Lunar Umbra

[mlsorensen]

I just wanted to drop a note from my own experimentation with a bespoke brew by weight setup. I found I could support the Umbra with existing Lunar code, with some minor tweaks:

• Look for “UMBRA” instead of “LUNAR” if you parse device names.
• Treat characteristic 0000FE41-8E22-4541-9D4C-21EDAE82ED19 on Umbra same as characteristic 49535343-8841-43F4-A8D4-ECBE34729BB3 on Lunar - “command characteristic”
• Treat characteristic 0000FE42-8E22-4541-9D4C-21EDAE82ED19 on Umbra same as characteristic 49535343-1E4D-4BD9-BA61-23C647249616 on Lunar - “weight characteristic”
• When decoding weight, it is now 4 byte big-endian whereas I had been decoding lunar as little-endian. Timestamp portion of the payload is still parsed the same (last 4 bytes, little-endian).

There may be other changes required for specific features, but the functions I use over BT just work (mainly tare command). In the future I’d like to dig into some of the newer features like the possibility of sleep/wake of the scale by turning the machine.

There seems to perhaps be a bug in the current Umbra firmware, it doesn’t report negative weight. For example if you tare with a cup and then remove the cup, the value is positive and there is no sign on the weight payload - even in their own Brewmaster app.

[mlsorensen]

Looks like the sign bug is fixed as of Umbra firmware 1.0.3

[mlsorensen]

Just a few more notes to help out.

Battery percentage comes through fine with no modification. Reporting of units doesn’t, but probably isn’t too important if you set it in the scale once and forget it.

This device doesn’t seem to need the heartbeat at all, which simplifies things if someone is writing a dedicated client from scratch, but it doesn’t seem to hurt using the regular Lunar code.

It also seems more reliable in sending weight notifications immediately first try. With the Lunar this was always a bit flaky and I had some workaround code.

Overall this device seems much better suited for integrations. You can set the device to auto sleep when idle, and it is discoverable while sleeping. This means you can just turn on the controlling device, let it connect and it will wake the scale. Then when you turn off the controller or disconnect the scale will sleep after the set time. Its main downside is lack of display, if you don’t have a separate one, but if you do then a lack of display and buttons is a plus.

[DarkWoke]

@mlsorensen @tatemazer

I’m developing a minimal iOS app to display live weight and tare of the Acaia Umbra Lunar scale and if possible "Turn on/off the scale". I’ve analyzed the Brewmaster and Artisan code, matched the UUIDs and command structure, and tried all known event/enable commands, but I only receive static weight values and tare doesn't work. I’d appreciate any guidance on the correct BLE sequence or protocol details.

1. BLE Protocol/Live Weight Streaming

• What is the exact sequence of BLE commands (including payloads and timing) required to enable live weight streaming from the Acaia Umbra Lunar scale?
• Is there a specific “event” or “enable notifications” command that must be sent to the scale after subscribing to the weight characteristic to receive live updates?
• Are there any required delays or handshakes between enabling notifications and sending commands to the scale?

2. Command Structure/Parsing

• Can you provide the correct structure and byte order for parsing the weight data from the 0x07 event? (e.g., which bytes represent the weight, factor, and sign, and are they big-endian or little-endian?)
• Are there any differences in the protocol or data format between the Umbra Lunar and other Acaia scales (e.g., Lunar, Pearl)?

3. BLE Characteristics/Descriptors

• Is it necessary to write directly to the CCCD (0x2902) descriptor on the Umbra Lunar, or is using setNotifyValue(true, for:) sufficient on iOS?
• Are there any additional characteristics or descriptors that must be written to (besides FE41 and FE42) to enable full functionality?

4. Tare/Command Issues

• What is the correct command and payload to send to the scale to trigger a tare operation?
• If writing to FE41 returns “Writing is not permitted,” what could be the cause, and how can it be resolved?

5. Troubleshooting/Best Practices

• Are there any known issues or quirks with the Umbra Lunar BLE implementation that differ from the documentation or other Acaia models?
• Do you have any sample BLE traffic logs (e.g., from nRF Connect or a sniffer) showing a successful session with live weight updates?

6. Open Source/Reference

• Is there any open-source code or documentation you recommend for correctly implementing the Umbra Lunar BLE protocol on iOS?
• Would you be willing to share a minimal working example (even in pseudocode) for connecting, enabling live weight, and taring the scale?

[tatemazer]

Hey thanks so much for the info! lovin the work you are doing on your project. Finally implementing this on my end, thanks again!

Just a few more notes to help out.

Battery percentage comes through fine with no modification. Reporting of units doesn’t, but probably isn’t too important if you set it in the scale once and forget it.

This device doesn’t seem to need the heartbeat at all, which simplifies things if someone is writing a dedicated client from scratch, but it doesn’t seem to hurt using the regular Lunar code.

It also seems more reliable in sending weight notifications immediately first try. With the Lunar this was always a bit flaky and I had some workaround code.

Overall this device seems much better suited for integrations. You can set the device to auto sleep when idle, and it is discoverable while sleeping. This means you can just turn on the controlling device, let it connect and it will wake the scale. Then when you turn off the controller or disconnect the scale will sleep after the set time. Its main downside is lack of display, if you don’t have a separate one, but if you do then a lack of display and buttons is a plus.

[mlsorensen]

@DarkWoke

I’m developing a minimal iOS app to display live weight and tare of the Acaia Umbra Lunar scale and if possible "Turn on/off the scale". I’ve analyzed the Brewmaster and Artisan code, matched the UUIDs and command structure, and tried all known event/enable commands, but I only receive static weight values and tare doesn't work. I’d appreciate any guidance on the correct BLE sequence or protocol details.

1. BLE Protocol/Live Weight Streaming

• What is the exact sequence of BLE commands (including payloads and timing) required to enable live weight streaming from the Acaia Umbra Lunar scale?
• Is there a specific “event” or “enable notifications” command that must be sent to the scale after subscribing to the weight characteristic to receive live updates?
• Are there any required delays or handshakes between enabling notifications and sending commands to the scale?

2. Command Structure/Parsing

• Can you provide the correct structure and byte order for parsing the weight data from the 0x07 event? (e.g., which bytes represent the weight, factor, and sign, and are they big-endian or little-endian?)
• Are there any differences in the protocol or data format between the Umbra Lunar and other Acaia scales (e.g., Lunar, Pearl)?

3. BLE Characteristics/Descriptors

• Is it necessary to write directly to the CCCD (0x2902) descriptor on the Umbra Lunar, or is using setNotifyValue(true, for:) sufficient on iOS?
• Are there any additional characteristics or descriptors that must be written to (besides FE41 and FE42) to enable full functionality?

4. Tare/Command Issues

• What is the correct command and payload to send to the scale to trigger a tare operation?
• If writing to FE41 returns “Writing is not permitted,” what could be the cause, and how can it be resolved?

5. Troubleshooting/Best Practices

• Are there any known issues or quirks with the Umbra Lunar BLE implementation that differ from the documentation or other Acaia models?
• Do you have any sample BLE traffic logs (e.g., from nRF Connect or a sniffer) showing a successful session with live weight updates?

6. Open Source/Reference

• Is there any open-source code or documentation you recommend for correctly implementing the Umbra Lunar BLE protocol on iOS?
• Would you be willing to share a minimal working example (even in pseudocode) for connecting, enabling live weight, and taring the scale?

This seems like a tangent from this issue, but anecdotally the major protocol difference I've observed between the Lunar and Umbra Lunar is that the latter doesn't seem to require a heartbeat. You can connect with a BT debugging app and it won't kick you off immediately, send commands manually etc. Things like tare seem to operate the same.

Of the half dozen or so scales I have the Acaia ones are the hardest to integrate, least straightforward. There are other examples but if you've already looked at this project, BeanConqueror, etc I don't know how much they would help. There is a python library for acaia in my Apollo project and a golang version in my goscale project, but I haven't gotten around to validating Umbra on that.

[DarkWoke]

@mlsorensen I got everything working already. The only thing that is not working is the correct battery level. To my understanding, the scale's firmware is bugged or something.

• Umbra Lunar’s FE42/EFDD status frequently reports a fixed 95% while external power is present, then flips to 100% only when charge terminates; near empty it can still report ~14–16% just before shutdown.

• Across sessions, explicit charging/not‑charging flags inside 0x0C/0x08 (e.g., 0x02 before 0x0D for charging, 0x01 for not) are inconsistent or missing; the standard GATT Battery Service (0x2A19) is typically absent.

• Result: the device exposes a coarse, display‑oriented percentage and intermittent power state, not a stable fuel‑gauge SoC, so apps cannot derive accurate 0–100% or reliably correlate percent with charging state without heuristics.

[mlsorensen]

@mlsorensen I got everything working already. The only thing that is not working is the correct battery level. To my understand, the scale's firmware is bugged or something.

• Umbra Lunar’s FE42/EFDD status frequently reports a fixed 95% while external power is present, then flips to 100% only when charge terminates; near empty it can still report ~14–16% just before shutdown.

• Across sessions, explicit charging/not‑charging flags inside 0x0C/0x08 (e.g., 0x02 before 0x0D for charging, 0x01 for not) are inconsistent or missing; the standard GATT Battery Service (0x2A19) is typically absent.

• Result: the device exposes a coarse, display‑oriented percentage and intermittent power state, not a stable fuel‑gauge SoC, so apps cannot derive accurate 0–100% or reliably correlate percent with charging state without heuristics.

I opened a support ticket with Acaia because even the brewmaster app reports 95% battery majority of the time right until it dies. They confirmed it is a firmware bug and are working it out with no ETA.

[DarkWoke]

@mlsorensen I got everything working already. The only thing that is not working is the correct battery level. To my understand, the scale's firmware is bugged or something.

• Umbra Lunar’s FE42/EFDD status frequently reports a fixed 95% while external power is present, then flips to 100% only when charge terminates; near empty it can still report ~14–16% just before shutdown.
• Across sessions, explicit charging/not‑charging flags inside 0x0C/0x08 (e.g., 0x02 before 0x0D for charging, 0x01 for not) are inconsistent or missing; the standard GATT Battery Service (0x2A19) is typically absent.
• Result: the device exposes a coarse, display‑oriented percentage and intermittent power state, not a stable fuel‑gauge SoC, so apps cannot derive accurate 0–100% or reliably correlate percent with charging state without heuristics.

I opened a support ticket with Acaia because even the brewmaster app reports 95% battery majority of the time right until it dies. They confirmed it is a firmware bug and are working it out with no ETA.

Just did the same. I don't think I'll hear from their CTO but who knows.

[DarkWoke]

Acaia released a new firmware for the Acaia Umbra Lunar. I did new BLE-sniffing but wasn't able to fix the battery level or the charging state even though they claim that it was "optimized".

https://help.acaia.co/hc/en-us/articles/37123852872852-Umbra-Firmware-Versions

[mlsorensen]

Acaia released a new firmware for the Acaia Umbra Lunar. I did new BLE-sniffing but wasn't able to fix the battery level or the charging state even though they claim that it was "optimized".

https://help.acaia.co/hc/en-us/articles/37123852872852-Umbra-Firmware-Versions

Firmware 1.0.7 fixes the "battery stuck at 95%" issue for my integration. I have since hacked in a 2000mAh lipo battery that's about the same size as the factory one so it lasts a lot longer anyway. Now I can tell when I need to charge though!

[DarkWoke]

Acaia released a new firmware for the Acaia Umbra Lunar. I did new BLE-sniffing but wasn't able to fix the battery level or the charging state even though they claim that it was "optimized".
https://help.acaia.co/hc/en-us/articles/37123852872852-Umbra-Firmware-Versions

Firmware 1.0.7 fixes the "battery stuck at 95%" issue for my integration. I have since hacked in a 2000mAh lipo battery that's about the same size as the factory one so it lasts a lot longer anyway. Now I can tell when I need to charge though!

@mlsorensen Please give me some informations how you show correct battery level and charging status. I am not able to get this working.

[tatemazer]

I've gotten my hands on an umbra. Unfortunately it crashes the ArduinoBLE library during the discovery process, looks like there are more features than the library can handle. This'll take some more in-depth work to support.

[theAddict]

Hey @tatemazer, I love the projects you've posted on YouTube. I just picked up an Umbra recently and was hoping to build a base for it with a display, as well as use it to hack brew-by-weight onto my Profitec. Your library looks like a good head start. Is there any part of the in-depth work that you'd be interested in help with? If not, not worries. Cheers.