@Jean-Philippe_Rey the VCC and GND pads are right next to each other on the edge, so you could solder a JST connector on if required. I did see if I could find space, but the board is just too small (unless I go for one of those micro JST connectors, but then it's hard to find batteries!).
The MOSFET-based solution is what the other 2 Espruino boards use. It's just painful to find space for it, and I imagine a lot of people would use a USB power brick anyway :)
@Ollie, @tve has done an awesome job with the ESP8266 port, but I think something like HTTPS would be almost impossible on it because of the lack of RAM - and that's what people will want for 'proper' IoT (and for even communicating with a lot of online services now). I could see the ESP8266 making a great board for local networks though - but many people make ESP8266 boards far more cheaply than I can manage, so anything I sell would look like a rip-off :)
Also, you're going to need some chip to do the USB connection - so if that chip were an STM32 then it could run Espruino :)
It would have been cool to have a bit on the end of the Pico for the ESP8266, but actually I think that there are a lot of people who would rather not solder at all - and if I'm going to do something that's tied to ESP8266, it's probably better to go all the way :)
@the1laz I'm keeping the pinout similar to the Pico, but there are more pins on the end, and the 'Bat' pin is removed and the pins on that side are shifted up by 1. It helps me keep more of the analog pins together.
I think smaller boards appeal to people a bit more, and actually it doesn't add too much to the cost. You're right about the crystal though - I think I found a good 8Mhz one (it's got the caps in, which saves money) but I still have room to put pads for a larger 32kHz crystal in, and I might do that.
@tve the regulator is the same microchip one as on the Pico (mcp1703) - 400mA max, ~200mA continuous, and I added a massive capacitor to keep the ESP8266 happy. It's not perfect - I'd thought about the switching supply you suggested, but it seems like an extra potential source of issues (noise when CE testing?) that I didn't want to worry about. I want to save as much time as possible so I really want to get as close to jamming an ESP8266 on a Pico as possible :)
Also, it seems like the switching supply might not have been able to 'step up' if the voltage got below 3.3v (that would have been awesome and would have swung it for me), and the input voltage range is pretty low. The regulator will run from at least 15v - although obviously at that it'll struggle with heat dissipation if 200mA is drawn for any big length of time.
@DrAzzy I've just removed the FET and resistor, so it's just USB->Fuse->Diode->5V->regulator now. The diode is just so you can't force power back into USB if you run from >5v and connect USB, it also gives the regulator a slightly easier time :)
I'm pretty sure I'll be using the STM32F411 - so very similar to the F401, but faster (100Mhz vs 84) with more Flash (512kB vs 384) and more RAM (128kB vs 96).
@asez73 I think with the ESP8266 on there, going after nA really isn't worth it. However I've been toying with the idea of doing some 'bare bones' Espruino boards. Something like 5 snap-out ones that are literally just an STM32 (no USB) and capacitors. The voltage range is 2-3.6v usually so maybe a schottky diode and you'd be able to run them safely off a LiPo with no quiescent current from a regulator. Selling 5 at a time would make it worth me selling them, while still keeping the per-unit cost really low.
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