Are you affected? If you have a tan colored H2T, your device is likely operating normally. If you have a green, red or black H2T get in touch with us.
We recently discovered an issue with some H2T and phone combinations where the Bluetooth (BLE) connection is unreliable or simply can't maintain a connection successfully. Curiously, in all our testing the initial Bluetooth connection is always successful and the issue starts specifically after the device reboots from first saving the LoRa region setting – but more on this later.
Here is a video showing what this issue looks like:
Testing and Development Before Release
With the H2T, as with every design we make, we tweak our color offerings a little bit to keep things fun and interesting. The most distinctive colorway we introduced for the H2T was the tan/brown combo and most of the initial testing was performed on this model. Actually, we only had one T114 board for development and throughout the design process we didn't see a single Bluetooth issue.
Once we finished the design, the next step was production validation and tweaking our print profiles for high volume. Once we decided on all the color options, we would be offering we tested one of each shortly before releasing the product. Here again we didn't have any problems connecting with Bluetooth.
Customer Feedback
Once our customers started receiving their H2T devices, we started hearing some cases of Bluetooth connection issues. By working with our customers, we collected data to correlate the issue with specific hardware, firmware and app versions.
More Testing
With this information we dove into collecting more data to investigate the issue. In the end we performed over 300 Bluetooth connection tests in total.
All testing was using firmware 2.4.2 Beta (the latest Stable version on the web flasher as of testing) as that is the version we ship units with. Note: some of the earliest units were shipped with 2.4.2 from the Github repository before the web flasher was updated.
1. Discovering the Material Effect
As we tested more and more devices, we found a correlation between the case color/material and isolated issues to the case colors: green, red, black that were using PLA-CF on the fronts instead of the PLA of the tan front. All tan (PLA) devices passed our testing so we took a sample of PLA-CF front devices, full results below.
| Test # | Device ID | BLE Connection | Range Test |
|---|---|---|---|
| 1 | 9bf2 | Unstable Connection | N/A |
| 2 | 0ee8 | Successful Connection | Did not test |
| 3 | 895c | Connection Loop | *Plugged in the connection was successful, over 20m of range |
| 4 | b5a9 | Successful Connection | Did not test |
| 5 | d0b6 | Connection Loop | N/A |
| 6 | f1ca | Successful Connection | Did not test |
| 7 | 025b | Successful Connection | Less than 1m |
| 8 | 91e9 | Successful Connection | Less than 1m |
| 9 | 9b77 | Successful Connection | Over 20m |
| 10 | c9ee | Connection Loop | N/A |
Tested with an iPhone 15 running app version 2.5.2.
Through our initial test we found a few peculiar results, for example the difference of plugging in the device in test #3. We separated more variables and continued testing.
2. Comprehensive Testing
We picked 5 devices for more extensive testing. The 3 with PLA-CF were picked specifically for presenting connection issues that we could reliably replicate.
Note: most of this round of testing was on a different phone, an iPhone 13 Pro Max running app version 2.5.1.
2a. No Case – Results are Number of Successful Connections out of 5 Attempts
| Distance | Device ID: 807b | Device ID: 141c | Device ID: 917a | Device ID: a5ea | Device ID: 5440 |
|---|---|---|---|---|---|
| 1 Foot | 5 | 5 | 5 | 5 | 5 |
| 20 Feet | 5 | 5 | 5 | 5 | 5 |
| 40 Feet | 5 | 5 | 5 | 5 | 5 |
Tested with an iPhone 13 Pro Max running app version 2.5.1
2b. Adding in Cases – Results are Number of Successful Connections out of 5 Attempts
| Distance | Device ID: 807b | Device ID: 141c | Device ID: 917a | Device ID: a5ea | Device ID: 5440 |
|---|---|---|---|---|---|
| Case Front | White PLA | Tan PLA | Black PLA-CF | Green PLA-CF | Red PLA-CF |
| Case Back | Black PLA | Brown PLA-CF | Brown PLA-CF | Brown PLA-CF | Brown PLA-CF |
| 1 Foot | 5 | 5 | 0 | 2 | 1 |
| 20 Feet | 5 | 5 | 0 | 0 | 0 |
| 40 Feet | 5 | 5 | 0 | 0 | 0 |
Tested with an iPhone 13 Pro Max running app version 2.5.1
2c. Testing different Phones – Results are Number of Successful Connections out of 5 Attempts
| Phone - App Version | Device ID: 917a | Device ID: a5ea | Device ID: 5440 |
|---|---|---|---|
| Case Front | Black PLA-CF | Green PLA-CF | Red PLA-CF |
| Case Back | Brown PLA-CF | Brown PLA-CF | Brown PLA-CF |
| iPhone 13 Pro Max - 2.5.1 | 0 | 4 | 0 |
| iPhone 15 - 2.5.2 | 2 | 2 | 1 |
| CMF Phone 1 - 2.3.15 | 5 | 3 | 5 |
| iPhone 12 Mini - 2.5.1 | 0 | 1 | 0 |
2d. Plugging in the Device – Results are Number of Successful Connections out of 5 Attempts
| Distance | Device ID: 917a | Device ID: a5ea | Device ID: 5440 |
|---|---|---|---|
| Case Front | Black PLA-CF | Green PLA-CF | Red PLA-CF |
| Case Back | Brown PLA-CF | Brown PLA-CF | Brown PLA-CF |
| iPhone 13 Pro Max - 2.5.1 | |||
| 1 Foot | 5 | 5 | 5 |
| 20 Feet | 0 | 0 | 0 |
| iPhone 15 - 2.5.2 | |||
| 1 Foot | 5 | 5 | 5 |
2e. PLA Case Back – Results are Number of Successful Connections out of 5 Attempts
| Distance | Device ID: 917a |
|---|---|
| Case Front | Black PLA-CF |
| Case Back | Tan PLA |
| 1 Foot | 0 |
| 20 Feet | 0 |
Tested with an iPhone 13 Pro Max running app version 2.5.1
2f. PLA Case Front – Results are Number of Successful Connections out of 5 Attempts
| Distance | Device ID: 917a |
|
|
Device ID: d376 |
|---|---|---|---|---|
| Case Front | Tan PLA | Black PLA | Orange PLA | Dark Green PLA |
| Case Back | Brown PLA-CF | Brown PLA-CF | Brown PLA-CF | Brown PLA-CF |
| 1 Foot | 5 | 5 | 5 | 5 |
| 20 Feet | 5 | 5 | 5 | 5 |
| 40 Feet | 5 | 5 | 5 | 5 |
Tested with an iPhone 13 Pro Max running app version 2.5.1
2g. Effect of the GPS Module – Results are Number of Successful Connections out of 5 Attempts
| Distance | Device ID: 917a |
|---|---|
| Case Front | Black PLA-CF |
| Case Back | Tan PLA |
| No GPS module installed | |
| 1 Foot | 5 |
| 20 Feet | 5 |
| 40 Feet | 5 |
| GPS off in software | |
| 1 Foot | 3 |
| 20 Feet | 0 |
| 40 Feet | 0 |
Tested with an iPhone 13 Pro Max running app version 2.5.1
Conclusions
As a summary we found four factors that play a critical part in the reliability of the Bluetooth connection, namely:
- Case front material (PLA-CF vs PLA)
- Presence of the GPS module
- Device plugged into USB power
- Phone model
Since we are aiming for the device to work well across all phone models, running on battery power and with the GPS module installed, the key change for us will be switching to a PLA Case Front.
Lessons for the Future
We have learnt a lot through this process and we are committed to continually improving our products and your experience using them. We will make sure for future products we have access to more boards and perform more comprehensive testing before release.
Now we have seen the Bluetooth performance difference across different phone models (trending to less connection reliability on older phones), we will keep a range of different phones in our testing procedure.
With better understanding of our materials, we learnt that the PLA-CF Case Back did not affect Bluetooth performance in the H2T but the Case Front was very much a factor. We will continue to explore new materials and evolve our designs to best make use of these materials.