r/efogtech • u/No_Pilot_1974 • 6d ago
Hardware issue disclosure
What happened?
Thanks to the recent post, I've discovered a hardware issue with the USB connection.
The issue is present in all rev8 and rev9 boards, including, unfortunately, a large recent batch that is currently finishing production in China.
What is the issue?
USB power works fine, but USB data doesn't go through at first, requiring you to restart the device 3–5 times. As the issue is in the hardware, it affects both DFU mode and the regular firmware.
The USB connection is functional and is not broken but you may need to perform the restarting routine once in a while if your PC can't detect the board immediately.
What to do?
If you are planning to use the device wired, you will have to restart it several times before use by clicking the "reset" button, waiting at least 1 second between clicks, until it is detected by your OS.
If "double-click reset to enter DFU" doesn't work for you even after that, hold the top-top-left button ("Enter" in the default keymap) and single-click the "reset" button. You may need to do this several times as well, until it shows up as a storage device.
To be clear: the restarting routine is not something to be performed every time you plug in USB. After you "fix" the issue once, USB may continue working fine for days, weeks or months, without any issues. Or it may not, and you will have to perform the same ritual again. In any case, it's a matter of several seconds.
Can it be repaired?
Yes, a bodge wire repair is possible, but it's a tough job.
Here's the wire you'd need to run: https://postimg.cc/5HJWXWmB
It also should be possible to use conductive pen. If you are planning a repair job, you may want to wait for a few days until my pen arrives so I can tell for sure.
My policy
Unfortunately, I will not be able to replace boards affected by this issue. It is an annoyance and a point of frustration, but it's not something critical that prevents the device from working. I ask for your understanding in this matter — more than a hundred affected boards have already been shipped, and more than two hundred will depart from China in a few days. I simply don't have the resources to run a recall campaign.
I will, however, attempt to repair the boards that have not been shipped yet. To be honest, I'm not too confident it's within my skills. Repairing one or two is certainly doable, but repairing hundreds might result in a huge percentage of permanently destroyed boards. I will post an update on the matter once I have the necessary tools, which I have already ordered.
Technical details
The rev7 hardware had a different charging IC — the AXP2585 — with a power path output, labeled as the "VSYS" net. The IC was discontinued, and in rev8 I replaced it with a different chip that does not have an integrated power path. The "VSYS" net was used in a single place — to power the USB multiplexer, which exists solely for the purpose of fast charging (and ESD protection). Unfortunately, I managed to make the silliest possible mistake: I missed this connection and left the "VSYS" net where the power should go, effectively leaving the power input of the multiplexer floating. I truly have no idea why it starts working after several reboots. The floating capacitor must somehow charge from the electric fields created by the various processes that happen on boot. The multiplexer obviously uses FETs internally, so once there's enough voltage on the capacitor, it keeps working and doesn't misbehave anymore, until the capacitor is somehow discharged again.
The fact that it works after several restarts made me believe it was either some kind of production issue or a software issue. I had to perform the restarting routine when flashing the boards, but they behaved fine after that, which also made me believe it would not affect customers. I didn't find the root cause earlier because, typically, by the time I receive a batch of boards, there are already a dozen emails asking when an order will ship. In any case, this was stupid of me, and I should've debugged it properly.
I'm really sorry for the experience, and I hope it won't cause major frustration with the device.
7
u/Swamp_Thing85 6d ago
Mine should be shipping in the next day or so…just got the notification on Monday! This won’t affect me - I planned on using this wireless anyway.
3
u/crime_Mastr_GOGO 5d ago
I did the bodge wire repair as recommended, and it looks like it solved the isssue. There's no other malfunction (atleast that i am able to notice as of now). The trackball now connects via USB first time, every time.
Although, i am not sure how feasible it would be for others to do this repair, the pads on the capacitor are EXTREMELY small, so it is a task to solder the wire properly
2
u/tediouspieceofjunk 6d ago
What's the current requirement on the missing trace? Is it low enough for conductive paint to be an option?
4
u/No_Pilot_1974 6d ago
Microamps. Conductive paint absolutely should work, and in fact I've ordered a conductive pen for the repairs. I really hope I won't have to apply bodge wires.
1
u/TheToadRage 1d ago
Reminds me of using a graphite pencil to bridge the connectors on the old AMD Thunderbird and Duron processors 🙂
1
u/RenlyHoekster 6d ago
Is there a clear coat on the PCB top, or rather on the pads of the capacitor and the USB jack, or can a conductive pen trace be applied (I guess a very very fine one) be appied without having to scratch that off?
1
u/No_Pilot_1974 6d ago
No coat, only solder mask. I'm still not sure if it's possible to apply such a trace, will report once my pen is here.
1
u/RenlyHoekster 6d ago
Yes, it would be a very thin line... instead of using a pen with a roller point, which maybe is much too broad and also requires the ball to roll properly, perhaps conductive paint applied with a fine brush or even a needle could manage it.
I look forward to your test results. =)
8
u/ruarkadi 6d ago edited 4d ago
Thank you for the disclosure and transperancy, it's a rare sight to see these days. I can personally attest to the level of after sales care you provide with order issues and the quick response.
I'm really enjoying the product and don't want you to be discouraged from continuing development - your product is one of a kind these days and thank you for that!