Have to unplug QC3 from wall to negotiate 12v

[pklapperich]

I have a Pinecil v2 and I've been using it with an 18w QC3 phone charger (5v@3a, 9v@2a, 12v@1.5a).

I have startup set to 0 = Off.

I've noticed that if I set the QC voltage to 9v and plug in the USB-C cable the Pinecil boots up and negotiates 9v. In this case it uses about 10w and does work OK. And if I set it to anything in the 9.4 - 12v and boot it up by plugging in the USB cable, then it powers up, blips like it's trying a higher voltage, but drops back to 5.1v. I thought it just wasn't going to work above 9v.

But if I plug in the USB cable before plugging the charger into the wall, it starts up just fine anywhere in the 9.4-12v range. It boots and shows 5.1v on the screen for a few seconds, then flips to 9v and ramps up to the final voltage. I also notice the voltage it settles on tends to be 0.4v lower than the QC limit in settings. So if I set it to 12.4v it actually settles on 12v during bootup and in that case it draws the full 18w while heating. If I set it to 12v it settles on 11.6v. If I set 11v it settles on 10.8v, etc.

So I guess if you're having trouble with a QC3 brick, try plugging in the USB cables to both the iron and the wall brick before connecting to AC.

Is there any reason from the Iron OS side that might be causing this? (Like does IronOS blip on the tip briefly as a test or something before the voltage has finished ramping?) Or just chalk it up to quirky behavior from this no-name phone charger ("Good-She Model GS-551")?

I'm using v2.21.5D96470. I had the same behavior on the firmware it shipped with (2.20 I think).