CubeCell Module Plus HTCC-AM02 can not upload Sketchwith Arduino


i have buy a CubeCell Module Plus HTCC-AM02 and build up a circuit how recommendet (HTCC-AM02 Recommend hardware designWith Arduino-Compatible)

When I connect it, i can read under COM5 and it accept AT commands:

Copyright @ 2019 Heltec Automation.All rights reserved.
AT Rev 0.8

But when i want to flash new code with Arduino (upload sketch), it doesn’t work:

Arduino: 1.8.13 (Windows Store (Windows 10), Board: "CubeCell-Module Plus(HTCC-AM02), REGION_EU868, CLASS_A, OTAA, ON, CONFIRMED, OFF, ON, DEACTIVE, None"
Der Sketch verwendet 80316 Bytes (61%) des Programmspeicherplatzes. Das Maximum sind 131072 Bytes.
[11804] Failed to execute script CubeCellflash
Initialising bootloader.
Traceback (most recent call last):
** File “”, line 3, in ***
*** File “”, line 769, in bootload.main***
*** File “”, line 646, in bootload.BootloaderHost.bootload***
*** File “”, line 688, in bootload.BootloaderHost.enter_bootloader***
*** File “”, line 471, in bootload.BootloaderSession.enter_bootloader***
*** File “”, line 466, in bootload.BootloaderSession.send***
*** File “”, line 218, in bootload.BootloaderResponse.decode***
bootload.InvalidPacketError: Expected Start Of Packet signature 0x01, found 0x80
bootload.InvalidPacketError: Expected Start Of Packet signature 0x01, found 0x80

Here a screenshot of the Signals during the upload period:

I have build up this circuit:

Try it

  • without pressing any key,
  • with pressing user, during power on
  • with pressing user --> Reset —> release Reset --> release user

Every time the same result…

What I’m doing wrong ?


Try it with a new board without any connections

I have success to upload sketch with continuesly hold press down the user button from power on until end of upload sketch. But this is not specified like this.

Hmm, very strange having the userkey pressed while releasing the reset you direct the board into the bootloader. as far as I know it is not checked anymore once it is in the bootloader.

Unless of course it is behaving differently for CubeCell Module Plus …


have you think this situation: the User key is a normally open switch. But you set the user key to a normally closed switch(in hardware).

maybe that’s why you met these abnormal situations.


the switch is definetly normally open. Otherwise the Signals will be not match. Here the Signals without pressing any key:


This Signals are taken during upload skech.

Yes, I have found this out through experimentation as well.
GPIO16 has to be tied to GND throughout the entire programming process. Reset is momentarily pulled LOW to bring the device into bootload mode.

And yes, this deviates from the specifications that Heltec put out.
I am using platformio to program HTCC-AM02


I have discussed with my colleague. as the picture shows, due to too many suppliers of components, may affect the bootloader. Please add a 100nf capacitor. Y6KGX1I5XZL60N%7B49EH334D