LED drivers and Accessories you want, but don’t exist

Schoki, since you mentioned that 3x3 MCU is the max you can fit I did some research…
Would Silicon Labs C8051F52x/3x series work?
They:

  • are available in 3x3 mm 10-pin DFN package
  • have 2-8 KB flash
  • have 256 B RAM
  • have a 8051 core, max 25 MHz
  • work in 1.7V-5.25V range
  • work in 40 125 °C
  • have a temp sensor and PWM
  • cost more than ATTiny ($2-$2.5 in small quantities)
  • can be programmed with open source tools on Linux and closed source freeware on Windows (dunno about Mac / BSD / …)
  • the programmer hardware costs $35

Though that said, the new attinies which we can’t program may be close enough to make the porting effort not worthwhile…

Thank you for looking for an alternative, i’ll look into it. But for now, I managed to squeeze an ATTiny25v on there, so bistro-hd would be possible.
The springpad is now smaller, but it should work (6.4mm diameter or so). It was possible because the ATTiny has one side of pins without any connection, so I removed these solder connections. On the other side, I just left the gnd pin.

One problem with other MCUs is that you have to change a lot in the code to make it run, so I hope it works like it is now.
I hope the 25v in a qfn package is a rev E at mouser. This is required to be able to run bistro-hd.

But since it’s a driver where a lot of current could flow, I maybe won’t even solder a spring on there. A piece of brass/copper could also work, and needs no bypass.

Hello.

Forgive me newbie question, but would it be possible to use something like TPS63024 for driving low Vf LEDs?…

If Vf is between 2.5V and 3.6V, yes.

Just ordered this, MP3431 board with (hopefully) bistro-HD:

It’s an 18mm board, but I’ll sand it down to 17mm to have copper right to the edge.

Ok, I finally found my way to thread instead of just the backroom PM discussions (that there have been a bunch of). Subscribed.

FWIW I've worked up a "Fet only" (ie single channel) configuration of bistro-HD (will be in next release, soon). Been meaning to anyway (actually a few such configurations, switch, indicator, OTMS, etc). It took a little compromising to match ramps to TA modegroups, mostly because without a 7135 you can't go below 11mA (1/255 * 2.8A) so modes get cutoff, but I've been thinking of ways to get around it.

16bit PWM, if the converter can actually handle such output or true, 2nd channel, enable pin PWM reduction, but Schoki says it's hard to fit the trace. 11mA ain't too bad though. It's not really moon, but it's low.

I thought I heard that this was going toward an attiny25 qfn, which I think is also on the scale of 3mm. Anyway, if you can make it still flashable (soic as shown), that's great.

For software though, if you need more space, the qfn becomes a drop-in replacement from the software side. Of course the qfn might make room for that extra trace.

It is attiny25 qfn, the tiny is on the underside. I removed the pads that aren’t connected internally of the attiny, the springpad is now a little bit bigger.

Is there a standard board or clamp or something you can buy to flash that or are you making up a flashing board too?

I use a USBasp and small wire that I solder on to flash it, for now.

You need 5 wires to flash. (power, ground, miso, mosi, sck) You're soldering them all by hand? Wow.

At some point it would probably be worth drawing a flashing board, that just connects via headers to the chip. It's got to be faster to just reflow it. Of course that requires work too.

Well, shoot only $85:

https://www.amazon.com/QFN-16BT-0-65-01-Programming-Adapter-Socket-Enplas/dp/B00KG7T8PU

So this is a buck driver?

If this works it would be nice to try to get one with Narsil

Also thought about a driver with a slave board to get more useful space

To solder and unsolder 5 wires for programming takes a minute, nothing wrong for a small to medium number of drivers

I don’t need the reset pin to flash?

It’s a 1S boost board.

oh, yeah, forgot reset. Yes you need that too. 6 pins.

So for testing it's actually possible to flash with debug wire, using only 3 pins. Two of those are power and ground. One is reset. So you could solder a wire to just reset on the board if you leave a small pad.

BUT, that uses debugwire, you'll have to flash fuses for that first anyway, and those fuses disable power-down sleep, which means OTSM won't work, so, so much for testing really. Could be useful for rapid e-switch testing, but not a very viable all around replacement.

Hey you still never told me what Vcc is powered by or I didn't understand. I need that to figure out LVP.

Just look at the PM, I sent you a picture. If it’s too small, open in new tab. LVP should be 3V or 2.9V.

Just simpler to ask. Ok. So that's a bit of trouble.

No time to explain right now, probably it will require LVP set at 3.1V, or high enough for tolerance to stay above the LDO. I'll explain later. OTSM has constraints on LVP and this doesn't fit the usual solutions very ideally.

So a little more detail. The issue is that to use the divider for LVP, the divider voltage must be kept above about 1.8V, (brushing over the details) to prevent off-click detection. To do that you need a high voltage reference to compare the voltage pin to. A 5.0V LDO on Vcc works well for that. 3.0V doesn't work as , more on that in a bit.

So for 1S builds, instead HD reads voltage from Vcc. But in that mode it's actually reading the battery voltage from Vcc, not some regulated LDO voltage. There are only two pins where the battery voltage can be read as a higher value than the internal reference used, those are Vcc and PB0 (only Vcc presently implemented in software). So that works for 1S with no LDO.

Now back to your thing. You can use the first method, but the problem is the voltage reading stops working once the battery hits the LDO level, or possibly slightly higher (some dropout in the LDO, not sure how much). Once the battery starts dropping below the LDO the sense voltage on pin7 and the reference voltage on Vcc start to drop at the same speed and the ratio doesn't change, so you peg the bottom of the scale there.

a) So this could work, but you'll lose sensitivity somewhere above the LDO voltage and must set LVP above that. You will also probably need different resistor values for the divider.

b) One suggestion would be to instead provide battery voltage to Vcc. You only need the LDO for the voltage filter not for Vcc. However, I'm guessing the reason you aren't doing that is that you don't want to use a separate protection diode. Speaking of which, you better use an LDO with low reverse leakage. I think the ones used on the small TA boards have worked.

c) Another possibility is to find an LDO that will work at 2.5V, but there's another problem you're running up against. OTSM doesn't have as much extra headroom at low Vcc. 2.5V may not work well at all, and/or may require more attention to good hardware selection as far as the cap and the leakage of the LDO. It could work though. My specs are a bit overstated, and exactly so that things like that might just work.

d) Yet another possibility is to make a hybrid voltage readout. So that it uses both Vcc read and Vcc referenced divider read. Vcc read will remain constant until hitting the LDO voltage, then it will drop and you can get extra range from that. From a software perspective though that could be tricky, because the way bistro polls the ADC, changing references requires delays, and there's already a switch back and forth from voltage to temperature and some difficulty orchestrating the timing for that. That's not my favorite solution.

e) Yet another option is to use a separate pin with a separate voltage divider, but I'm pretty sure you have no space for that.