I have never needed an external pull-up on the reset pin, the internal pull-up sufficed. However, in noisy circuits, an external pull-up (typically 10k, maybe even only 4.7k, but not less than that) is often recommended, because the internal one is quite weak (~50k). My guess is that the FET switches much quicker than the AMC7135, which indeed implies more noise. It might help to check the reset pin with an oscilloscope.
A resistor between MCU and gate is also often recommended.
Would comparing the code that works to the code that doesn't help to nail down what the issue is? I don't understand it well enough to know what the differences translate into in actual use...
Also, for a temporary test, I can use a plain jumper wire from Vcc to RST instead of a resistor, right? Just don't try to program it with that in place (it would block the clip anyway)...
Here's a mouseover of the 17DD showing what's underneath
The diode could be rotated about 30* CCW to free up a bunch of space for fatter traces in & out. Also looks possible to pop in a via near the RST pin and add a resistor on the spring side of the board, if it turns out that's needed.
That's actually a very good point. Every FET based circuit I've ever worked on prior to this (so um...one lol) has had a 100ohm resistor between the MCU and FET gate. I think the reason I skipped it here was because the original SRK board never used one either, and I was lead to believe it work fine? That being said I know what it's there for so I should have included one regardless.
10k pull up on the reset pin to VCC will now be included on all my boards by default.
When I get the time to update some of these boards (and some sort of testing prior would be good) I will update the OSHPark projects.
Anyone who has ordered any of my boards and is experiencing problems, can you please PM me?
The JB driver with the single 2SK4212 FET didn't use a resistor to the gate, and worked fine with any of the right firmware versions and before any mods using the stock unknown MCU and also after the piggyback 105C was added... it still works without the resistor on the new 46mm version, the only issue with that one is the noise from certain versions of firmware. Lack of a resistor shouldn't affect the smaller board if it doesn't also affect the larger one, I would guess.
Is there a pull-down resistor on the FET gate? Without one the FET could come on between the time the processor is powered up and it initializes the state of the output pins. Try something around 1K to 10K from the FET gate to ground.
None of the other boards have needed a pulldown on the gate using the same components.
I've tried jumpering various stuff at random: from B+ to the diode, and from the diode to MCU's Vdd, neither made any difference. But I then moved the jumper to go straight from Vdd pin to B+, bypassing the diode, and it now changes mode like it should, doesn't do that weird random strobe/morse code crap, doesn't change 2 modes when it should only do 1, etc. The diode isn't on backwards, could it just be a bad diode? I doubt it, since the battmon mode in luxdrv gives the correct number of blinks that matches the input voltage.
OK, progress, of a sort: the old standby version of luxdrv works properly with the diode removed & replaced with a jumper.
edit: Of course, the voltage monitoring is off without the drop from the diode, it gives 13 blinks for a cell with only 4.1v. But at least this is getting somewhere.
See my edit above about the voltage detection. Also, it can't be programmed while the jumper is in place. The LEDs turn on when the clip is attached & plugged in. So obviously this isn't a solution, just a good clue as to what's wrong.
Does anyone know what the exact diode is on the Nanjg 105C? I have though I had finally figured it out about 6 times by now, still no closer than when I started, looks like.
I tried a couple of different SMD resistors between the MCU and GATE, 100 ohm and 200 ohm, they both work and function fine. Did some searching and reading (still over my head) but from what I could gather this should ease the load significantly on the MCU. Definitely worth a shot for those of you who are having trouble.
For testing purposes I just bent up the leg and soldered the 0805 SMD resistor between the pad and FET leg. In future boards pads could easily be placed for a gate resistor.
I think it's the same one, which is the one from Digikey marked "41". It worked fine for me without any tweaks at all (without the gate resistor) using STAR 1.1 set to 0x21 (phase correct).
I wanted to test this out because DBCstm has had a few of these FET drivers die, including one that I built for him. Smoked the traces and on another one where he bypassed the traces the MCU may have died. Was thinking that our extra capacitors were just a bandaid for the true problem, which was excessive inrush current load when the gate is being charged. This is just a SWAG, I haven't taken any measurements with my fancy HF DMM or anything like that.
Don't mind the solder blobs, I've had stuff on and off a few times on this board. I went "tombstone" style.
