Big ESP32 / SX127x topic part 1

Looking at your picture, it looks like they use a MCP73831 (or compatible) charging IC (the 5-pin SOT23 below the helical coil). The default behaviour of the STAT pin is to blink while charging (or no battery connected) and to turn off when battery is full.

This is from one of my designs, which also uses a green led to indicate battery full.


Some more interesting ‘nuts and bolts’ hacking at the Espressif chips by Andreas Spiess, this time getting both processor cores of the ESP32 working using the Arduino IDE only. Seems like this can only help with more complex tasks?

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I ordered micro JST off Ebay and they work fine. Downside is that they come in pairs, so I now have a number of micro JST male in-line connectors…

Which exact model is ‘Micro JST’?
I am unable to locate it on the JST site: JST Product Selection Guide
None of their 1.25mm connectors looks like the one on the Heltec board.

I think that the Heltect board uses a Molex PicoBlade Header:
1.25mm Pitch PicoBlade Header, Surface Mount, Right Angle, 2 Circuits

Cables Assemblies:
PicoBlade-to-PicoBlade Off-the-Shelf (OTS) Cable Assembly, Single Row, 2 Circuits

25mm PicoBlade 2 Circuit Cable Assembly

I ordered ebay item 232485892646 - it is just described as micro JST 1.25mm. They fit fine - pic below shows one alongside my test rig that is now being powered by a LiPo.



Good to hear that these ‘JST 1.25mm’ connectors do fit.

25mm PicoBlade 2 Circuit Cable Assembly
Molex PicoBlade 1.25mm

25mm female cable assembly
‘JST 1.25mm’

I have added a link for ‘JST 1.25mm’ cable assemblies in the Bargain Basement: The BARGAIN basement part 3

I was very interested to see the video about using both of the main cores of the ESP32 (, but even more excited to see in the comments an example sketch using the ULP - ESP32: ULP LED Hart beat and read DHT22 sensor · GitHub - to try this you will need to have installed the current ESP32 hardware support for your Arduino IDE - GitHub - espressif/arduino-esp32: Arduino core for the ESP32

Has anyone managed to get the power usage of these modules below 10ma? Even in deep sleep and with wifi/BT off I can’t manage it with a battery. Are they maybe using a low efficiency regulator that keeps on switching?

Received mine finally.
The antenna is quite different looking from what was in the aliexpress pictures.
They also provided a miniature heatsink - probably for the ESP32 chip ?

Wifi Lora Kit 32 868 - package

Now I must find some time to play with this…

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I was wondering about that too, until I read about “fever” in the document you provided earlier :wink:

ESP32 is a highly integrated chip QFN package, due to high frequency, small size and not easy to heat, so when used in the higher fever is normal, Our company has done a complete stability assessment of the circuit t,Pls no worry about it ,and if you very care about the head you can add heat sink by yourself.

Found a new place discussing those boards at

It mention someone designed a nice 3d printable case :

I finally found the official board page on Heltec site. Maybe they improved the site navigability or I was just not awake enough last time I tried.

No new information as far I see, but it’s probably worth bookmarking in case they update the docs, etc.

Original :

English by google :


@F_Dam posted this link elsewhere:

Black PCB, blue charging LED, battery cable included, better English description and above all (if one gets delivered what is advertised):

  • different kind of WiFI antenna
  • different (positioned) battery connector
  • some component engraved “SL” is now underneath the battery connector, but seems to be above it (and marked S4) on my HelTec boards (moved to make room for the different antenna?)
  • two mounting holes

Branded TTGO/WEMS instead of HelTec, so now wondering who really made the PCB design. Some shops even name it Wemos. But lists “TTGO LoRa” as:

“WeMos” / Lily GO (not group)
Clone of Heltec Automation’s WIFI LoRa 32 board

The same shop is selling a case, which certainly needs a different WiFi antenna to fit the module. It’s also available in black:


Searching for ttgo oled "lora" gets a lot of new search results, like:

The module can also be found without an OLED display, for just US$ 9.00 (but a different WiFi antenna, if one gets what’s shown):


Also, I ran into with easy instructions to get the Arduino IDE running for the (HelTec) board. (I’ve not tested that; for me the instructions on HelTec’s GitHub work fine too, but need some Git commands.)


I’ve order one, since neither I have a ESP32 yet, and the price for this around 10€ with lora is quite good. Even cheaper than the diymall atmega32u4 lora based boards. But probably only in January I’ll receive it :slight_smile:

And in fact what also caught my attention was the antenna ( I know that those existed since I’ve receive samples of them, but never used) so let’s see how they behave, and the same shop sells the case. But the case might not be very useful since it has no space for anything else, like sensors or whatever.

Edit: The sl marked component looks like a diode? Probably to protect reverse polarity, since the battery cable is provided.

Hi @arjanvanb … i’m having the same problem … does anyone successfully used Lora.onReceive to call a function for when a packet is received? Thanks

The antenna might be better but it is positioned very poorly. It is surrounded by metal pins and positioned on the module’s bottom side so the PCB will shield the RF signals on the top side and a breadboard or base PCB where the module will be mounted on will shield RF signals on the bottom side (almost like a Faraday cage).

Antenna is like the one used on this board:

Will you keep us updated if you manage to find it, please?

Sure but I’m not searching very actively (just ordered a RAK831).

I already have one :wink:
And I am hesitating: to buy another or to wait for RAK832.
But still I would like to have a decent 1-channel gateway to compare signal strengths etc - to keep tabs on multichannel gateway, basicaly

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Not sure if this was the question - but, the antenna looks like the ones from Swedish company ProAnt -

I have been told by the UK distributor that these bent metal antennae don’t require a ground plane and can mounted over components

Note that ProAnt are behind the tuned cavity antenna on the Raspberry Pi Zero W