Hi everyone,

This is my very first post on this forum, and I’m reaching out for help and advice regarding an off-grid solar inverter I purchased from a Chinese manufacturer (appears to be a Voltronic-Axpert-VM-4-TWIN-4KW-6KW, firmware 56.09). I hope in the future to contribute back to the community.

Unfortunately, the inverter consistently goes into fault mode after just a few minutes of operation.I reached out to the manufacturer through their English website and support section, but my inquiries were ignored. After some research, I assumed that upgrading the firmware via an Ethernet-to-serial cable might resolve the issue. However, this attempt unfortunately completely "bricked" the inverter instead of fixing it (it is no longer reachable with the Ethernet-to-serial cable).

Since the manufacturer hasn't responded to my emails requesting a spare control board, I’m now considering more technical solutions like JTAG or off-chip programming as a last hope. Since this is new territory for me, I would greatly appreciate any guidance or tips from the community on how to proceed with these methods:

1. How to identify the JTAG port on the control board

2. The procedure for programming the chip (TMS980320F28062PZTG4A)

Thank you in advance for your help!

Edited May 7, 20251 yr by Axlotl
missing pictures were too big

3 hours ago, Axlotl said:

How to identify the JTAG port on the control board

It's the 14 pin header with pin 6 missing, near the DSP chip.

3 hours ago, Axlotl said:

The procedure for programming the chip (TMS980320F28062PZTG4A)

You purchase an XDS100 compatible JTAG interface from Ebay, Ali Express or the like. Generally these come with an easy to use flashing program. They are reasonably priced.

But the bad news is that genuine Voltronic firmware is password protected, and we don't know the password for these models. It's possible that a clone inverter won't bother with the password, but that's by no means guaranteed. You can erase the entire flash area, but this will erase the boot loader as well. If you have a JTAG interface, you could give up on the bootloader and replace it with a single jump instruction, and always update the firmware using JTAG. But then the Voltronic firmware will detect this and stop working after 60 days. You could patch the firmware to prevent this, but you have to really know what you are doing.

It's also not guaranteed that genuine firmware will run on clone hardware. They may have cut corners, or changed some DSP pin assignments to avoid copyright violation.

So I'm sorry to say that things are looking grim. That's the downside of buying a clone.

I discuss many of the JTAG issues here:

3 hours ago, Coulomb said:

You can erase the entire flash area, but this will erase the boot loader as well.

Are you sure there's some "easy" way to do it? I mean, the flash registers are protected by CSM password too. I was not able to erase the flash using Uniflash when the CSM password was programmed.

@Axlotl You can replace the chip with a new one, modify the firmware file to work without a bootloader and upload it using JTAG. The problem is that there may be no suitable firmware for this model available online. Which firmware version did you try to upload? Did the process finish correctly?

When flashing the correct version of the software with the standard update program, it is difficult to completely kill the inverter. Even if the inverter is not fully flashed and stops turning on. Even if the inverter does not turn on, the boot loader remains intact. You need to press the power button in time during the start of the update program.

It is not possible to read the firmware using JITAG on this model. The firmware is protected by the manufacturer with a 128-bit password.

What version of the software was installed in the inverter and what version of the software was flashed?

Edited May 9, 20251 yr by biletskiy