i do not understand why these GPIO input protections have to be so elaborate.
Then I think really Aixun should be more helpful in this regard and offer to send you a pre-flashed MCU. For a few bucks spare parts charge. If they want to preserve their firmwares.
@dreamcat4: careful with just this component on the GPIO pin, its datasheet lists 35V clamping - check it against the GD32F303 datasheet, where page 51 lists:
VIN:
Input voltage on 5V tolerant pin(3) VSS - 0.3 ... VDD + 3.6 V
Input voltage on other I/O VSS - 0.3 ... 3.6 V
and footnote 3 lists:
(3) VIN maximum value cannot exceed 5.5V.
This may not mix well enough in terms of protection. It will be better than nothing (35V is waaay better than several kilovolts!), but alone this particular component may not be sufficient... Just IMHO :-).
Also, if selecting a TVS with lower stand-off voltage - check its datasheet for leakage current, if I recall correctly, at least some TVS lineups show notable leakage for lower nominal stand-off voltages. If leakage current is tangible - it could pull the GPIO level down far enough to make MCU think it's a logic zero (or keep flapping in and out of zero randomly).
ah ok... looking at the datasheet for the 0603ESDA-MLP1,
Then I think really Aixun should be more helpful in this regard and offer to send you a pre-flashed MCU. For a few bucks spare parts charge. If they want to preserve their firmwares.I wrote to Aixun technical support. They didn't answer.
I described my problem here earlier.
Then I think really Aixun should be more helpful in this regard and offer to send you a pre-flashed MCU. For a few bucks spare parts charge. If they want to preserve their firmwares.I wrote to Aixun technical support. They didn't answer.
I described my problem here earlier.
... working on that "problem"
Excellent! Thank you.
Now you need to purchase a programmer for GD. I have one for STM, but it won't fit.
I'll try programming again. If it does not work out, then I will buy a new processor and flash it.
But it's not soon - I'm in no hurry. I also have other soldering irons. And also the main work that takes time.
P.S. I looked at Aliexpress programmer GD-Link. Very expensive (compared to STM programmer)
Hi all,
I got my T3A yesterday
Well, schematics in 3... 2... 1... https://github.com/c0d3z3r0/aixun_t3a_schematics
Hi all,
I got my T3A yesterday
Well, schematics in 3... 2... 1... https://github.com/c0d3z3r0/aixun_t3a_schematics
which board revision is this for? there are 2 different revisions. sadly all of mine are the original ones while i wish they were the newer one but im curious. ahh now i see it was rev 1.2. all of mine are on 1.1.
i wish i could get new boards for the front they seem to be okay for the most part but we did loose 2 of them now. i have not had time to go through them yet but its not the power supply on them. one will not recognize the tip inserted, tried brand new handle from another unit that has never been used before and works fine in another t3a. and the other no longer controls the temp properly. it shows proper temp on screen but turns the tip bright red.
i do wonder if either of these would have been better protected with the 1.2 revision.
i have been out of the office and no one is sure what happened to either. we did have some random power outages but nothing else has been damaged. i have been away from the office due to cancer treatments. so far out of the 20 we lost those 2. they did have a lot of time soldering on them though. kind of sucks if i waited like a month we would have 1.2 units not that it may have saved these 2 but i do wonder. so far no response from them when i asked if i could buy new board or even a whole new front panel for them. they only responded offering to sell me 2 units for normal price.
i have personally been mostly using the 420d at home over the t3a or t3b lately since bringing it home. i do have 3 brand new t3a i never used i may end up selling just because i have the 420d now. they do have the older stand though undecided yet.
ah ok... looking at the datasheet for the 0603ESDA-MLP1,
@dreamcat4: I'd try something like this: ti esd351
also wanted to know if we need anymore tvs elsewhere. for example on the thermocouple adc input. but it should already be buffered behind the op-amp right?
also wanted to know if we need anymore tvs elsewhere. for example on the thermocouple adc input. but it should already be buffered behind the op-amp right?When I check the schematics (thanks c0d3z3r0 !) - I see that there are total of three MCU-leading lines, one is the input I've put protection on (stand detect aka "Port1"), also there is "ID" and there is "Shake" . The remaining two are traveling "to outside" through the wiring towards the handle, so technically - also need to be protected. But... in order to add TVSs - one would need to access the front board, which is behind the glued front acrylic panel... Also, those inputs are in a more controlled environment, not as exposed as the back-panel stand sensing input. So, all in all I will probably pass on trying to add protection to these (and another one - temp sensing via opamp)... Too much hassle.
For myself I'm settling on just being careful ESD-wise when disconnecting (rarely if ever!) the handle connector from the base. I'm not in a high-speed manufacturing environment, so when I change the tips - I don't mind to turn off the base and do it in a controlled fashion, letting the tip to cool down before swapping it. Time for a cup of tea :-). This reduces the risk of mishaps during tip removal and insertion. And again, I rest my hands on a dissipating, grounded mat when I swap tips.
If I recall correctly, one of the users has menioned earlier in this trail that the "no dormancy" problem started once they have swapped the tips. I'm just thinking common sense here - hot tip, mechanical contacts surrounded by plastic, plus likely non-original quality of plastic and accuracy of handle manufacturing. Softened plastic moves under mechanical forces, contacts touch where they shouldn't, maybe arcing, maybe sending +24V down the signal lines... Lots of things could go wrong...
Will see how my T3A will behave under my light use, hopefully it will last. I'll keep checking this message trail as well :-).
The stand detect input (PORT1) is heavily at risk of both air and contact discharge in both models.
...
Well, I don't want to disappoint you, but shit happens Also, see above (charged device model).
thinking about finding two connectors (male & female) matching the ones used on the base & handle. Between those connectors we can place proper TVSs between each exposed MCU line and ground, maybe in a tiny metal enclosure (similar to RF filters/measurement equipment input dividers, etc.). Then the new "adapter" can be left permanently attached to the base and the exposed side will have "TVS-ed" lines only... Hmm... :-)
The stand detect input (PORT1) is heavily at risk of both air and contact discharge in both models.
...
Well, I don't want to disappoint you, but shit happens Also, see above (charged device model).That's exactly why I did protect the stand input with optocoupler plus ESD protection of the +24V rail I had to use for the LED side of the optocoupler. From a risk management perspective - I'm satisfied with this balance.
BTW, the Charged Device Model implies transition of: "no contact with ground, no potential" --> "potential build-up (via tribocharging/induction)" --> "contact with a path to ground, discharge!".
With the handle attached nearly permanently to the base, chances are there is always a path for potential to continuously flow towards ground, without much chance for high-level potential to build up...
those "T4" reverse-protection diodes (likely equivalent of 1N4148) are not ideal, they do have reverse leakage current of at least few uA, so any slow electrostatic potential buildup (regardless of + or - ) will likely leak via that diode, 4K7 resistor, to power rail, through the power supply circuits, towards ground. At 5uA (that is at 75V reverse, at 20V reverse it leaks less, but still not zero) - it's equivalent of 15 megaohm.
The primary risk for those pins is when the handle gets connected / disconnected. Keep it connected and when you do disconnect - don't stick your charged pinky into the connector on the base (or touch its rim first) :-). With connect/disconnect transactions minimized - the risk is minimized as well. I also suspect that in T245 handle those detection wires either are not connected or looped to the ground right in the handle's connector (except the T sensor) - not much point in running long wires to the actual handle, our friends in China would rather save $1 on that extra copper :-). Even less chance of static induction.
NOW, you've provoked me to think outside of the box, literally. I got an idea now - we can introduce protection without ripping the front panel!
I'm now thinking about finding two connectors (male & female) matching the ones used on the base & handle. Between those connectors we can place proper TVSs between each exposed MCU line and ground, maybe in a tiny metal enclosure (similar to RF filters/measurement equipment input dividers, etc.). Then the new "adapter" can be left permanently attached to the base and the exposed side will have "TVS-ed" lines only... Hmm... :-)
I admire your determination to make AiXun's product better. Now that you've modified the firmware - you may want to think about how to prevent auto firmware update. If AiXun software (Windows) doesn't make any further checks (like refusing to update a firmware with unknown checksum/hash) - it may silently overwrite the modified firmware with a newer version, on connection - your modifications could be lost then... Or just remember to never install their software again :-). Good luck in your endeavours!
thinking about finding two connectors (male & female) matching the ones used on the base & handle. Between those connectors we can place proper TVSs between each exposed MCU line and ground, maybe in a tiny metal enclosure (similar to RF filters/measurement equipment input dividers, etc.). Then the new "adapter" can be left permanently attached to the base and the exposed side will have "TVS-ed" lines only... Hmm... :-)
see i like this thinking. however (for completely un-related reasons).... i did not want to put that extra little PCB in the back of the main base unit for myself. because (in my mind) I was hoping that perhaps there was enough room back there to somehow relocated the GH5 connector from the front of the unit. to the back of the unit. just to make the wiring more neater.
however also another idea I was hoping might be possible was making the cradle an extension for that same GH5. and pass thru the handle wire via the cradle.... except this t3a cradle is made of plastic and does not actually have a gh5 connector on it. But there is another version of the stand (perhaps for t3b?) that does?
[edit] and possibly changing the gh-5 aviation connector for a gh-6. then no longer need that extra seperate wire for the idle detection (labelled in port 1). because then you can remove that jack from the back of the base station and make some room to relocate the gh-5 (---> gh-6) connector itself. maybe also remove the other +24v dc output barrel jack. and or remove or relocate the esd jack on the read panel too
anyhow... so with either of those above 2 mods. then perhaps might also give the necessary opportunity to add those TVS diodes on the GH pins? to be a bit less clunky?
Inspired by cfg5 user I made modification to new aixun t3a stand. I like the fact that I can change tips quickly same as with jbc stand.
Another mod i want to look into is push rod to back panel power switch. However that requires getting out the hot air station. To remove glue of the front plastic.