Suggestions please: ESP8266 "Base"-Board with pyboard Footprint

Discussion and questions about boards that can run MicroPython but don't have a dedicated forum.
Target audience: Everyone interested in running MicroPython on other hardware.
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kfricke
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Suggestions please: ESP8266 "Base"-Board with pyboard Footprint

Post by kfricke » Mon Sep 12, 2016 2:10 pm

What do you think of the idea of a ESP8266 "Base"-Board with a pyboard footprint? What i have in mind is something more pyboard-like but based on the ideas of this and other boards.

I am not capable of designing board layouts, maybe someone is keen on providing (and open-source) board designs for a ESP-WROOM-02 based board with a full or half pyboard foorprint?
The ESP-WROOM-02 is similar to the AI-Thinker ESP-Modules and seems to be Esspressif's own most recent incarnation of ESP8266 modules. It can be purchased for quite low price tag (~4 €), has it's own RF shield and 16MByte flash module.

I could think of some bare-metal features around this module like:
  • All GPIOs exposed to the "full pyboard" footprint, important ones to a half one
  • Jumper or button for the entering UART mode for flashing the ESP
  • Jumper to connect GPIO16 to RST to enable deepsleep wakeups
  • Jumper and voltage divider (high ohm resistors + cap) to connect VIN to the ADC (TOUT pin)
  • Power supply only micro-USB port with an efficient 3v3 step-down converter (NO USB-serial chip)
  • Serial port accessible by attching the USB-TTL, which nearly every ESP developer does own, to the exposed pins
The above should even be possible on a small board which can be hand-soldered using through-whole components instead of SMD parts (okay, all but the micro-USB port, make it an JST connector than). Every hardware hobbyist i know does own a USB-serial adapter and can program the toy by hand, given he has a stable 3v3 300mA power supply (like this puppet has onboard).

Basically it should look somehow like this dirty draft (actual proportions should somewhat match):
pyb-WROOM-02.png
pyb-WROOM-02.png (109.43 KiB) Viewed 3746 times
The further demands for the missing features of such a board could be answered by more half-pyboard-footprint addons (shield/hats/<you-name-it>) like:
  • A real USB-TTL adapter board
  • A fully fledged LiPo charger board
Such addon boards might on the one hand open a better utility board economy than available at present and will also tackle issues with more restricted ports to MCUs with no on-chip DFU and the like.
Why stuff all these features onto the main board when the final embedded device on the field does not sue it anymore? We have the fantastic pyboard as THE development board already!

Things like battery connector and LiPo charging circuitry is a waste on the ESP imho anyways, because of it's quite high power constraints. Only a few months on battery does not provide enough low-power capabilities imho. A step down converter with a wide input voltage range (4-12v) is more interesting.

TBH, i do not have any clue about parts to be used in this puppy!

edit: a small addition to the above: It would be nice to just provide the files for a double-sided PCB board, which everyone could order on pcb manufacturing sites like OSH-Park or others.

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deshipu
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Re: Suggestions please: ESP8266 "Base"-Board with pyboard Footprint

Post by deshipu » Mon Sep 12, 2016 4:24 pm

So I tried to make a quick and dirty mockup of such a PCB in Fritzing (http://fritzing.org). The first problem I had is that the WROOM-02 board is too wide to fit between pyboard's pins. So I used an ESP-12 module instead, which has the same pins, but is much smaller. It looks something like this:
pyboard-esp8266_pcb.png
pyboard-esp8266_pcb.png (97.55 KiB) Viewed 3720 times
I had to make no new footprints, just used the parts that are already available in the library. I had to edit a transistor part to rename it to a HT7333 voltage regulator, and rename the pins on it, but that's cosmetic.

You can get the file with the design here: https://bitbucket.org/thesheep/eps8266p ... sp8266.fzz
Attachments
pyboard-esp8266_pcb.png
pyboard-esp8266_pcb.png (42.98 KiB) Viewed 3725 times
Last edited by deshipu on Mon Sep 12, 2016 4:42 pm, edited 1 time in total.

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deshipu
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Re: Suggestions please: ESP8266 "Base"-Board with pyboard Footprint

Post by deshipu » Mon Sep 12, 2016 4:27 pm

Notes: as you can see, ESP8266 has a considerably smaller number of available GPIO pins, than the pyboard. One of the pins is analog-only. It would probably make sense to first analyse the existing shields and note which pins are used by them, so that we can make informed decisions about where to put each pin.

Turbinenreiter
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Re: Suggestions please: ESP8266 "Base"-Board with pyboard Footprint

Post by Turbinenreiter » Mon Sep 12, 2016 4:57 pm

Honestly, if you do a board like that, put an I/O Expander on it. Generally I think bare-bones boards are even less universal than full packed boards. I guess your idea is to have a cheap board to leave in projects? Then why not go as bare as the module itself? An LD33V is all you need for voltage regulation, deadbug it russian style and done.
Then again, for a permanent installation, you'd want a board for the peripherals anyway, why not just design one?

Also, in choosing boards to be Pin compatible with, why the pyboard? The form factor didn't exactly catch on and there is next to none expansion boards for it.

Adafruits Feather form factor however has a whole lot of expansion boards. Why not just use their Huzzah boards? If you wanna drop cost, the Eagle files for that board are Open Hardware and it could be easily modified (I'm willing to do that - edit: I just did, it takes like two minutes to remove all the parts you don't want. An hour to check and recheck everything and it's good to go. Checkout here).

You guys just need a crash course in Eagle ;)

(Not trying to 'shit' on your idea, just trying to provide constructive feedback.)
Last edited by Turbinenreiter on Mon Sep 12, 2016 5:27 pm, edited 3 times in total.

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Roberthh
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Re: Suggestions please: ESP8266 "Base"-Board with pyboard Footprint

Post by Roberthh » Mon Sep 12, 2016 5:00 pm

There may be the usual confusion in the specs. Espressif talks about 2 MBytes = 16 MBits of flash, with possible up to 16 MBytes. The first supplier I picked (Watterod, 4 €) offers 16MByte devices, Microtechnica talsk of 4 MBytes, so there is some ambuigity.
If I think about costs of parts and PCB (6-10 $ at small volumes, unless you make it yourself), the difference between this board and maybe Huzzah feather is minor. The latter has USB and LiPo support included. Not to talk about a Wemos D1, which just has USB at a 6$ price tag. Obviously you can gain experience doing that anmd tailor it to your own need.

SpotlightKid
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Re: Suggestions please: ESP8266 "Base"-Board with pyboard Footprint

Post by SpotlightKid » Mon Sep 12, 2016 6:01 pm

The Pyboard form factor also isn't very friendly to breadboarding. If you solder male pin headers to it and stick it in a breadboard, it covers all the middle lanes and leaves no place to plug you jumper wires or other components. The huzzzah/nodemcu form factor is much more practical in this regard.

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deshipu
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Re: Suggestions please: ESP8266 "Base"-Board with pyboard Footprint

Post by deshipu » Mon Sep 12, 2016 6:39 pm

SpotlightKid wrote:The Pyboard form factor also isn't very friendly to breadboarding. If you solder male pin headers to it and stick it in a breadboard, it covers all the middle lanes and leaves no place to plug you jumper wires or other components.
The trick is to put the pins in the middle on top, and only put the two rows on the sides on the bottom.

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deshipu
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Re: Suggestions please: ESP8266 "Base"-Board with pyboard Footprint

Post by deshipu » Mon Sep 12, 2016 6:40 pm

Personally I consider this is great opportunity to learn making PCBs in Fritzing (easier in my opinion) or Eagle (harder, but more popular).

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kfricke
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Re: Suggestions please: ESP8266 "Base"-Board with pyboard Footprint

Post by kfricke » Mon Sep 12, 2016 7:13 pm

deshipu wrote:Personally I consider this is great opportunity to learn making PCBs in Fritzing (easier in my opinion) or Eagle (harder, but more popular).
I did download eagle a few months back and got a positive detection of a trojan... After some digging around i noticed this was somehow true. Call it "they do offer it for free, so live with it" or "other free software does not need this kind of sh*t"... if i would learn a CAE design tool, i'd choose KiCAD.

Maybe i'll give Fritzing another try on this one before taking more time to dig into PCB design.

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kfricke
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Re: Suggestions please: ESP8266 "Base"-Board with pyboard Footprint

Post by kfricke » Mon Sep 12, 2016 7:20 pm

Roberthh wrote:There may be the usual confusion in the specs. Espressif talks about 2 MBytes = 16 MBits of flash, with possible up to 16 MBytes. The first supplier I picked (Watterod, 4 €) offers 16MByte devices, Microtechnica talsk of 4 MBytes, so there is some ambuigity.
If I think about costs of parts and PCB (6-10 $ at small volumes, unless you make it yourself), the difference between this board and maybe Huzzah feather is minor. The latter has USB and LiPo support included. Not to talk about a Wemos D1, which just has USB at a 6$ price tag. Obviously you can gain experience doing that anmd tailor it to your own need.
Good points to be honest, but missing my suggestion.

You are of course right about the Wemos, but the bare-metal design could be built by hand and the serial USB part is wasted for a field unit.

The Feather boards are even more different. They are full packed with features but still lack field-ready features when using their battery powered features. Why do they design a LiPo "subsystem" without the possibility to track voltage. Simply stupid imho! Of course implementing one with a p-channel MOSFET to switch everything off is wasting space on the board, which they lack obviously.

Both are different leagues to play in tha a bare-metal approach i think.

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