H32 Ultralow idle power ESP32 development platform (3.5uA)

[soubitos]

What is it?
H32 is an Ultra Low Power ESP32 platform. It is designed to make connections to additional electronics (sensors etc) a lot easier using spring terminals and, once your project is past the development stage you may need a custom expansion board with the additional electronics but NOT a whole ESP32 board with power management etc.. these are taken care for by H32. This makes it cheaper and faster to deliver the finished project for deployment.

Why did you make it & what makes it special?
Almost everybody involved with ESP32 has at some point used a "typical" devkit most of which have terrible power management circuitry for a battery powered project you want to develop. Almost everybody who has worked with a "typical devkit during project development hates the myriad of not so easy to work with wires with pin headers which if not of really good quality can cause problems either electrical (cheap wires with huge resistance) or mechanical (getting loose easily after few uses). not to mention one wrong move can remove a bunch of wires and have you start from scratch. Typically you will breadboard a devkit connect sensors etc to it and once you're done you most likely need to design a custom board to host the devkit and additional electronics. Although in theory its possible to bring an ESP32 in a very low power mode, using a normal devkit usually increases the "idle" state power consumption from hundreds of uA to a few mA even. You also cannot power a devkit from a wide voltage range and most of the time they are designed to use with LiPo or protected Li-Ion as they dont have battery protection onboard.

H32 was designed to solve all these problems and more. Instead of trying to achieve low idle power consumption with the ESP and everything else onboard powered H32 shuts down system power completely achieving an ultra low idle power consumption of aprox 3.5uA. The onboard fuel gauge will turn on power if battery goes critically low and so will any sensor you add or any kind of switch like reed switches or floater switches. H32 fits inside 100x100mm waterproof electrical junction boxes (some are bigger inside than others, you need to find a suitable enclosure but many in the market do fit, H32 was designed to fit a specific model we can source from the Greek manufacturer) H32 has a 500mA single cell Li-Ion charger with battery protection as well as an I2C fuel gauge which are responsible for the well being of the onboard 18650 cell. Power source can be anything DC from wall adapters to solar panels with voltages between 5 and 30V. When in off state a solar panel can recharge the battery and if turned on and solar panel delivers enough power there is a power path making sure battery stays charged and system receives power from external source.

TIMER
H32 operates based on a power management circuit controlled by active low signals. Besides the Power Button & Fuel Gauge which can both turn on power, H32 is using an RTC by EPSON in order to turn on and off on its own based on a time interval which can by dynamically changed based ie on battery status or a sensor reading etc. This means H32 is particularly suited for applications where a physical event is monitored for changes over time or, has a very sporadic and irregular occurrence. A good example is that of a remote water tank where a floater switch triggers H32 when water level is low and H32 can use for example an NB-IoT or LoRa modules to send an alert to the end user that tank needs to be refilled. While waiting for this event, H32 can stay OFF waking up once every few days even in order to verify battery status and send a signals confirming its still active.

GPIO
All GPIO from Ai-Thinker's ESP32-S (ESP32-WROOM-32) except GPIO13 are available to the user.. GPIO13 is used to shut down power when system is ready.. it is still accessible in order you want to implement a different shut down approach.

EXPANSION BOARDS
We have prepared a prototyping board but are working on application specific expansion boards ie LoRa or NB-IoT or Beekeeping with a load cell interface etc. Main system power and battery power are also available for use.

SENSOR
An AHT21 I2C humidity & temperature sensor is onboard H32 for basic readings..

FIRMWARE
Firmware for H32 has been developed by Joachim Baumann and you can find it here https://github.com/jbaumann/H32_Basic Current version supports H32 rev2 but firmware for rev3 is in development as we speak and should be ready in the following weeks.

PROGRAMMING
There is a 6pin programming header with access to POWER, RESET, GPIO0 & RX/TX A matching USB adapter is specially designed for H32 and can be purchased here https://www.tindie.com/products/28221/

H32 will increase your creativity, expand your battery runtime and help you go from idea to finished project faster and easier than any other devkit in the market today.. did we mention it only consumes 3.5uA when idle???

H32 is available on tindie https://www.tindie.com/products/soubitos/h32-rev3-ultra-low-power-35ua-esp32-platform/

[moep]

Looks like quiet a nice low power ESP32 development platform. 

In your Github repository you've explained how you measured ~250nA power consuption while here and on Tindie you're mentioning 3.5uA. Were the 250nA measurements from a previous revision?
Also I couldn't find any schematics or hardware design files: any plans on releasing them? Especially for development platforms they would be handy - I don't like to reverse engineer my development platforms when something doesn't work as expected (Yes I do mess up things often ). That overview graphic on your Github at least gives a rough idea, but it's missing some information (23 & 24) and seems outdated (Revision 2), too.

Some of the information that I'd consider essential seems missing (or maybe I'm blind):
1.) How much power can be drawn from that 3.3V rail?
2.) Working voltage range for the LiPo battery?
3.) Which over-/undervolltage protection voltages are configured for the LiPo? That's important information for selecting the correct battery and not causing a fire hazard...
4.) Vin acceptable voltage range and current rating needed for the external power supply.
5.) Is there any reverse polarity protection on Vin and/or the battery? Or should the user just be careful?
6.) Which I2C fuel gauge IC was used? This is required to know on how to interface with that chip

[soubitos]

Thank you soo much for all the right questions
I am not releasing schematics (not in full really) before I can secure my production and have at least recovered some of the investment involved (took some 2 years and 2 earlier revisions to get to this point).
There are 2-3 critical components I am trying to either secure in stock or replace which means more prototyping for me wooohooooo!

Github is maintained by Joachim in Germany who is expecting rev3 boards to update firmware etc soon.
I estimate by the time the first rev3 boards reach their customers we should have new example firmware and updated info.
To be honest rev1 and 2 were so small batches that at this point we dont want to invest more time on them but will certainly do it once rev3 firmware is ready and production and sales ramp up.

Power measurements are made with Nordic's power profiler.
Rev1 was MUCH different and indeed had a super low power consumption..
There was a back boost converter for 3V3 rail which in rev2 was replaced by a simple LDO as it was both too costly and most importantly not available
The main difference in power consumption was in the battery power measurement circuitry as on rev1 I used a mosfet and voltage divider but on rev2 replaced it by a low cost (but slightly more power hungry) load switch.

1. 3.3V rail on rev1 was set for max 900mA and on rev2 & 3 at 800mA
2-3. On rev1-2 Battery protection kicks in @2.8V for under voltage conditions but allows only 900mA discharge. Charger is set to 500mA. Battery protection is set to 4.25-4.3Vmax
4. External power source can range from as low as 5-6V but for better efficiency 8V are suggested and up to 30V. (It will work if you attach 5V but its best to exceed 8V)
5. User should just be careful I am afraid.. Working on power management for rev3.1 next with lots of changes and improvements.
6. Fuel Gauge is MAX17048 which is pretty much the only low cost FG I can source without supply issues but also does the job. (couple alternatives come as BGA which I cannot handle atm)

Practically I will release a schematic on github for all revisions but I will have power management as a block so, for the end user point of view it should allow working with the board know internal connections of the ESP (well, everything else is pretty much I2C anyway) but not the power management circuit in details which as I said I dont feel comfortable revealing yet (I know its not rocket science but its just me I guess)... in time I am considering making fully open source but not right now...

[soubitos]

H32 is now in rev4 and its available on Tindie https://www.tindie.com/products/28380/