Smaller Espruino board?

@Gordon are there any plans for the future to create a smaller Espruino board like the size of the Teensy++ 2.0?

Yes, there are plans :) I started the design 3-4 months ago, but it's been delayed quite a bit! The board is 0.1" thinner than the Teensy so the pinout's got to be chosen to make the tracking easy.

I actually ordered some prototype PCBs last night, so hopefully I'll have some working hardware in 2 weeks or so.

Rough specs are:

• 35x15mm
  
• Printed Type A USB connector
  
• 0.1" pad layout, 28 GPIOs
  
• Roughly the same spec ARM
  
• Onboard 32kHz crystal
  
• Same power supply arrangement as the Espruino board - automatic switchover to battery, 3-20v input voltage range
  
  

I'm quite excited about it. It should be a lot easier to include in things and much easier to breadboard with...

Hi Gordon,

Fantastic news. A little bit more memory too ? Do you accept preorders ? ;-)

Sacha

@Sacha, yes - it's looking like it'll have 64kB instead of 48. I was considering an even higher spec, but really the plan is to get the cost down as much as possible so it becomes more of an impulse purchase :)

I will almost certainly KickStart this one again as the last one brought in so much publicity - I'll definitely let everyone know on the forum/twitter/etc when it goes up!

Perfect.

on-board wifi would be nice :-)

@possmann - that's not going to happen I'm afraid. It's so small there's barely enough room to get the required components in!

It'll be pretty easy to stick the Adafruit Wifi dongle on though. You should be able to solder it straight on.

it was just a small dream imagination :-) at the moment, i'm a little bit spoiled by the spark core. so just ignore my illusions ... ;-)

@Gordon, could you please give some more information to this
It'll be pretty easy to stick the Adafruit Wifi dongle on though. You should be able to solder it straight on.
Is it for the new board only, and which dongle do you have in mind ?

BTW, does anybody have some experience with HLK-RM04 Serial Port-Ethernet-Wi-Fi Adapter

This is exciting - I'm amazed at how tiny the new board will be - ~1.4 x 0.6 inch. So 28 GPIO pins? Is it settled yet what kind of capabilities those pins will have (ie, how many I2C, hardware SPI, PWM, etc)? I assume that would be determined when the chip is selected.

Will it have a builtin MicroSD reader?

Also, what does a "Printed" usb connector mean?

@Gordon, awesome news! I can't wait until its available for purchase. Do you have an estimate time frame when you will be alerting us when the kickstarter goes live?

@JumJum - I'll be trying to add support for different pins for WiFi (and every GPIO on the new board is 5v tolerant), so you should be able to solder the CC3000 on anywhere as long as you wire up gnd + vcc. I just mean the standard Adafruit module.

On the existing board, the pinout was arranged such that you can solder the CC3000 straight on with only 2 extra wires needed - gnd + vcc.

@DrAzzy the chip is the F401, so it's 3 SPI, 3 I2C, 2 Serial, ~8 analog in, and PWM on almost every pin. By printed USB, I just mean something like the DigiSpark. It's not fantastic, but it makes the board really thin, doesn't need a cable, and it won't ever snap off :) It also means you'll be able to just push it into a mains adaptor/battery pack for power.

No built-in Micro SD I'm afraid - you'd have to solder something on for that.

@d0773d - I don't know about timings yet... I guess when I get the first prototype back and assemble it I'll have more of an idea. I'd hoped for the beginning of September, but everything has gone a lot more slowly than I'd expected so I doubt I'll manage that now. Maybe mid-september.

Great news!!

@Gordon How's it going with the smaller board? How many pins will it have? Is it too early to say something about its price?

I really like the prospect of a tiny "plug-and-play" Espruino board. I think a printed USB connector is a great idea, and the smaller form factor is perfect for a couple of projects I have planned.

If one still wants a board on a wire (like a drunk in a midnight choir?), one could always use an extension USB cable.. I see no downsides to this, and plenty of advantages!

So what's below is what I have so far. You'll have to excuse the soldering - 0403 parts are a bit tricky :)

It's got:

• 1 button (not fitted in this pic)
  
• 2 LEDs
  
• 32kHz + 8Mhz crystals
  
• Same automatic battery/USB switchover as the Espruino board
  
• pads for JST battery connector on the rear
  
  

It's got pretty much every pin brought out but having played with it I'm reconsidering that now... If you imagine that there were just the two strips of pins down the edges it could be made almost 1cm shorter - and if you're using protoboard then the pins going across are effectively useless anyway.

As far as price, I haven't costed it up fully but it's designed to be easier to manufacture than the Espruino board. I'm aiming for something around £15 each on the KickStarter, maybe a bit more afterwards (as distributors need their cut too).

I totally miscalculated the US suggested retail price of the original Espruino board (sales tax is added afterwards in the US) so distributors are making a much higher margin there. Hopefully I'll get it right with this new board and it'll compete more sensibly with the Arduino Micro.

1 Attachment

sales tax is added afterwards in the US

In the US, unless PUR3 has a "brick and motar" location in the state(51 states) then you can charge the going sales tax. The sales tax varies between state to state. There is no sales tax charged to the individual buying an Espruino from the UK!
Adafruit, which is your US distributor, in New York state, can only charge sales tax only for New York residences NOT individuals in another state! Ordering an Espruino from Adafruit from another state no sales tax is applied.

@user7114 thanks! That's good to know... strange arrangement though - so it's cheaper to buy from Adafruit anywhere other than New York?

You got it! - "spot-on"
New York "city" sales tax 8.875%

BTW ...
What you need to do is sell in a low tax state like Colorado (average 2.90%) which
doesn't discourage buying your Espruino due to high sales tax like New York.
Guess who is in Colorado? - SparkFun.

Better yet, directly sell through Tindie.com

@Gordon That looks really nice! (Not your soldering, understandably, but the board overall.)

Thanks for the detailed answer. Really looking forward to holding one some day.

I'm not sure which is most important, 1 cm smaller or 12 more pins.. It would be small enough for my needs if it was like in the photo.

I am curious about the number of insertions/retractions on the "gold fingers" before
they are not usable?

Sexy sexy sexy!

I am in favor of 12 extra pins over a 1cm board size reduction - without those pins, you'd have what? 16 GPIO pins? That's just not enough, imo (*). Are those 4 holes near the USB connector breakouts for the USB pins? I don't see those being very useful for most people (assuming there's an accessible GND/vbat somewhere).

For someone stuffing the board into a solderless breadboard or perf board, maybe it would make sense to ensure that those middle pins would be the ones for use with WiFi/Ethernet modules - I'm envisioning the pins being put facing the opposite way in those holes, so the WiFi module could ride on top of the EspruinoMini as it sat in the perf board... That'd be neat, for sure.

The internet sales tax gravy train is gonna end sooner or later. It's thanks only to political gridlock that they haven't closed that loophole already.

• - On the Espruino 1v3, one could argue that it has more pins than it needs, particularly given the memory limit - I doubt one could fit code that would use all 40-odd pins without running out of memory even with 3250 jsvars. 16 GPIO pins only is too far in the other direction, though - that's into pin-starvation land. Stick a keypad on it, and bam, there's half your IO, gone!
  

@user7114 - lots of insertions. The nice thing about the USB connectors is that all the sprung contacts are in the socket, so you really can get away with something very simple for the plug. If you look at those tiny WiFi/bluetooth USB donges, they do something very similar as well.

@DrAzzy / @Joakim Thanks for the feedback about the pins...

• Yes, those 4 at the end are USB. The reasoning was that you could then solder a pin header socket on and push the board directly onto a PC motherboard, but you can just surface mount it on the normal USB connector anyway. I've already pulled them out of the next prototype.
  
• If I dropped the extra pins but put pads for an SMD pin header on the other side, would that work for you? Then it's tiny, but still has the pins if you need them. I feel like if I'm going to make it small, I should make it impressively small :)
  
• As for WiFi/Ethernet I'll try and get the SPI ordering right - I'm very limited though because there's so little space for tracking. I'm toying with the idea of tweaking Espruino to allow use of different pins for Wifi/Ethernet/filesystem (which I should do anyway) and then maybe also allowing software SPI - in which case you could just attach the modules wherever you wanted.
  
  
  

I'd be interested to hear your thoughts on the power supply. I've kept the same as the original Espruino (minus the fuse), but I think it's overkill. Effectively it means you have pins for:

• USB voltage in (maybe just on the USB connector)
  
• Battery voltage in (and JST battery connector pads on the rear)
  
• Bat/USB voltage out (this is Bat on the Espruino board)
  
• 3.3v out
  
  

Personally I think that's too much, and a little confusing... I think a lot of people expect a little board like this to just have Vin, and maybe 3.3v out.

I guess one cool side effect is that I've connected the FET to a GPIO, so if you're running Espruino from USB you actually get one powered output for free, which you could use for speakers/relays/etc.

hi, I designed small board with newest stm32f072cb crystall less usb, integrated all usb resistor
https://oshpark.com/shared_projects/7YeHJutX
rgb led
reset button
usb rom bootloader
on edge connector is spi,iic/uart,dac
but 072 is only 128kb flash

I have tested one board, working dfu usb bootloader :-)

• Re: USB - makes sense.
  
• Re: SMD pin header - what do you mean by "SMD Pin Header"? Are we talking the ones that are like normal pinheader with the ends bent 90 degrees so you can surface mount it? Or some sort of higher density connector? In the latter case, connector selection (to get something that is readily available and easy to find) would be important to making it useful. I had a wonderful awful idea - what if the pads were right along the end, at 0.1" spacing... then you could take a 2-row pinheader, put it on the edge, and solder it to the pads (so one row was on the top, the other on the bottom) - this'd be kinda ghetto though.
  
• FS/Network anywhere without having to recompile the firmware would be nice.
  
• Re: Power... I'm not sure how you could change the power supply without degrading the usefulness of board - you need to be able to power it off of USB, and safely connect it to USB when it's also got external power on it (for in-place development/debugging/monitoring/etc of an espruino in something with an external power supply) - so those voltages are going to have to exist somewhere, even if not broken out anywhere other than the USB and JST headers. You certainly can't leave the 3.3v pins - if someone's using a voltage higher than 5.x volts, they'd have to wire up a regulator or stepdown to get power for connected devices, which'd be no fun.
  
  

On the topic of power, I don't suppose there's space for pads for a MAX155x (SOT-23-5)? You expressed interest in this last time it was brought up, and for the kind of portable applications that an espruino the size of a flash drive seems good for, being able to add automatic battery charging when plugged into USB by dropping on two parts (the header and the MAX155x) would be sweet...

@bobricius looks great! Can the 32k crytal be fitted while still using onboard usb?

SMD: yes, I meant with the ends bent over. I had considered a side-soldered connector (like bobricius, but at 0.05") but it turned out to be too hard to track. Going back to 0.1" could work though. I might give that a try.

MAX155x: no chance, but pads for this are on the rev 1v4 normal board which will be heading to distributors soon.