Not receiving any data from HMS-1600-4T

[JesseJanssen]

What happened?

Good morning,

Two days ago I received and set up the CASmo-DTU, I have two Hoymiles inverters installed for my solar panels (HMS-800-2T and HMS-1600-4T) and the 800-2T works pretty much flawlessly but I cannot get the 1600-4T to work with the DTU. I have been Googling, trying all "solutions" I have so far found (But to no avail unfortunately), I have also been on Discord in the support-opendtu channel and managed to flash the latest version of OpenDTU to the DTU (OTA updating wasn't working at first, since the newest version is now installed I don't know if it works now but that's not a big problem), I have tried several frequencies (865.0MHz, 868.0MHz, 868.75MHz) and several transmitting power options (Currently at -5dBm) and the RSSI is ~-61dBm when I have the DTU at my computer for testing. For some reason the 1600-4T has a "RX Success" less than 5% since I've been trying and never have actually seen it working in the OpenDTU Live View. Do you have any suggestions what could help me with my issue?

If you need it, the serialnumber for the 1600-4T is; 1164a028xxxx

To Reproduce Bug

Connect a HMS-1600-4T (Maybe same serialnumber range) and see if it works?

Expected Behavior

Receive data from the HMS-1600-4T just like the HMS-800-2T is doing, which works flawlessly.

Install Method

Pre-Compiled binary from GitHub releases

What git-hash/version of OpenDTU?

v26.3.30

What firmware variant (PIO Environment)?

generic_esp32

Relevant log/trace output

Anything else?

No response

Please confirm the following

• I believe this issue is a bug that affects all users of OpenDTU, not something specific to my installation.
• I have already searched for relevant existing issues and discussions before opening this report.
• I have updated the title field above with a concise description.
• I have double checked that my inverter does not contain a W in the model name (like HMS-xxxW) as they are not supported.

[ththeimer]

Hi, I would suggest trying channels near 865 MHz, like 850.25, 850.50 and so on, also below 850. -62 dBm is not good, how far is the DTU from your inverter ? What is the RSSI for the other inverter ?It looks like there is a signal but it‘s just not strong enough.BR, ThomasAm 11.05.2026 um 09:38 schrieb JesseJanssen ***@***.***>:JesseJanssen created an issue (tbnobody/OpenDTU#3063) What happened? Good morning, Two days ago I received and set up the CASmo-DTU, I have two Hoymiles inverters installed for my solar panels (HMS-800-2T and HMS-1600-4T) and the 800-2T works pretty much flawlessly but I cannot get the 1600-4T to work with the DTU. I have been Googling, trying all "solutions" I have so far found (But to no avail unfortunately), I have also been on Discord in the support-opendtu channel and managed to flash the latest version of OpenDTU to the DTU (OTA updating wasn't working at first, since the newest version is now installed I don't know if it works now but that's not a big problem), I have tried several frequencies (865.0MHz, 868.0MHz, 868.75MHz) and several transmitting power options (Currently at -5dBm) and the RSSI is ~-61dBm when I have the DTU at my computer for testing. For some reason the 1600-4T has a "RX Success" less than 5% since I've been trying and never have actually seen it working in the OpenDTU Live View. Do you have any suggestions what could help me with my issue? If you need it, the serialnumber for the 1600-4T is; 1164a028xxxx image.png (view on web) image.png (view on web) image.png (view on web) To Reproduce Bug Connect a HMS-1600-4T (Maybe same serialnumber range) and see if it works? Expected Behavior Receive data from the HMS-1600-4T just like the HMS-800-2T is doing, which works flawlessly. Install Method Pre-Compiled binary from GitHub releases What git-hash/version of OpenDTU? v26.3.30 What firmware variant (PIO Environment)? generic_esp32 Relevant log/trace output Anything else? No response Please confirm the following I believe this issue is a bug that affects all users of OpenDTU, not something specific to my installation. I have already searched for relevant existing issues and discussions before opening this report. I have updated the title field above with a concise description. I have double checked that my inverter does not contain a W in the model name (like HMS-xxxW) as they are not supported. —Reply to this email directly, view it on GitHub, or unsubscribe.Triage notifications on the go with GitHub Mobile for iOS or Android. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[JesseJanssen]

Hello Thomas, Thank you for the quick reply, the RSSI is lower when I place the DTU closer to the inverters, for testing now I have it placed about 6/7 meters away from the inverters with a wall inbetween them but for how far I noticed the results are the same with lower (< 50 or even < 40 RSSI) or higher (60+ RSSI) and that is that the HMS-800-2T functions perfectly and the HMS-1600-4T doesn't function at all. I have tried your suggestion, I started at 864.00, tried 864.25, 864.50, 864.75, 865.00, 865.25, 865.50, 865.75, 866.00, 868.00, 868.25, 868.50 and 868.75 but on some frequencies both inveters won't respond and on some frequencies only the HMS-800-2T responds, not giving any progress in the matter... Do you have any other ideas what might help me with this issue? Best regards, Jesse Op ma 11 mei 2026 om 11:31 schreef ththeimer ***@***.***>:

…

*ththeimer* left a comment (tbnobody/OpenDTU#3063) <#3063 (comment)> Hi, I would suggest trying channels near 865 MHz, like 850.25, 850.50 and so on, also below 850. -62 dBm is not good, how far is the DTU from your inverter ? What is the RSSI for the other inverter ?It looks like there is a signal but it‘s just not strong enough.BR, ThomasAm 11.05.2026 um 09:38 schrieb JesseJanssen ***@***.***>:JesseJanssen created an issue (tbnobody/OpenDTU#3063) What happened? Good morning, Two days ago I received and set up the CASmo-DTU, I have two Hoymiles inverters installed for my solar panels (HMS-800-2T and HMS-1600-4T) and the 800-2T works pretty much flawlessly but I cannot get the 1600-4T to work with the DTU. I have been Googling, trying all "solutions" I have so far found (But to no avail unfortunately), I have also been on Discord in the support-opendtu channel and managed to flash the latest version of OpenDTU to the DTU (OTA updating wasn't working at first, since the newest version is now installed I don't know if it works now but that's not a big problem), I have tried several frequencies (865.0MHz, 868.0MHz, 868.75MHz) and several transmitting power options (Currently at -5dBm) and the RSSI is ~-61dBm when I have the DTU at my computer for testing. For some reason the 1600-4T has a "RX Success" less than 5% since I've been trying and never have actually seen it working in the OpenDTU Live View. Do you have any suggestions what could help me with my issue? If you need it, the serialnumber for the 1600-4T is; 1164a028xxxx image.png (view on web) image.png (view on web) image.png (view on web) To Reproduce Bug Connect a HMS-1600-4T (Maybe same serialnumber range) and see if it works? Expected Behavior Receive data from the HMS-1600-4T just like the HMS-800-2T is doing, which works flawlessly. Install Method Pre-Compiled binary from GitHub releases What git-hash/version of OpenDTU? v26.3.30 What firmware variant (PIO Environment)? generic_esp32 Relevant log/trace output Anything else? No response Please confirm the following I believe this issue is a bug that affects all users of OpenDTU, not something specific to my installation. I have already searched for relevant existing issues and discussions before opening this report. I have updated the title field above with a concise description. I have double checked that my inverter does not contain a W in the model name (like HMS-xxxW) as they are not supported. —Reply to this email directly, view it on GitHub, or unsubscribe.Triage notifications on the go with GitHub Mobile for iOS or Android. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***> — Reply to this email directly, view it on GitHub <#3063 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AC2RX2KCW4QIY2FZVYZHCCD42GMVNAVCNFSM6AAAAACYYWXDUGVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DIMJZGI4DQMBRGA> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>. You are receiving this because you authored the thread.Message ID: ***@***.***>

[JesseJanssen]

This is the result when the DTU is placed close to the inverters, little changes in RSSI but no changes in that the 800 works and the 1600 doesn't..

[ththeimer]

Well, if one inverter is functioning fine while the other one doesn‘t, it is likely not the DTU that is causing the issue. The problem is that you would need a Hoymiles DTU to get support from Hoymiles. An official DTU would also help verify if the 1600 is working or not. But that is probably not what you want to hear.In general, your RSSI is a bit on the low side, but it is good enough for the communication to work. Not much more I can add here, sorry.ThomasAm 11.05.2026 um 16:36 schrieb JesseJanssen ***@***.***>:JesseJanssen left a comment (tbnobody/OpenDTU#3063) image.png (view on web) image.png (view on web) image.png (view on web) This is the result when the DTU is placed close to the inverters, little changes in RSSI but no changes in that the 800 works and the 1600 doesn't.. —Reply to this email directly, view it on GitHub, or unsubscribe.Triage notifications on the go with GitHub Mobile for iOS or Android. You are receiving this because you commented.Message ID: ***@***.***>

[JesseJanssen]

Thank you for your insights, so there is nothing more I can do? I have actually been running the inverters on the "Hoymiles DTU Pro S" up until I received the CASmo DTU, I'm a Home Assistant enthusiast and like to have as much local control as I can, plus I believe I can't actively limit the inverter power with Hoymiles (only persistent, not non-persistent) so that's why I want to switch.

[ththeimer]

So I assume that everything is working fine with the official DTU. I can see your point, that is why people like using OpenDTU.When you have multiple inverters, there is a chance that they may switch to different / incompatible frequencies. That is a problem as the OpenDTU can only run at a single frequency. I am not sure that that is your problem, but it shows that there may be cases when OpenDTU is causing problems. I run a single 2000-T and that works fine as long as I can follow its frequency changes. Your 1600-T probably has the same radio interface implementation.You don‘t know what exactly has been negotiated previously between that inverter and the official DTU. I also don‘t know if there is a way to do a factory reset on the 1600 via the Hoymiles DTU. If there is, I would try that.Am 11.05.2026 um 23:13 schrieb JesseJanssen ***@***.***>:JesseJanssen left a comment (tbnobody/OpenDTU#3063) Thank you for your insights, so there is nothing more I can do? I have actually been running the inverters on the "Hoymiles DTU Pro S" up until I received the CASmo DTU, I'm a Home Assistant enthusiast and like to have as much local control as I can, plus I believe I can't actively limit the inverter power with Hoymiles (only persistent, not non-persistent) so that's why I want to switch. —Reply to this email directly, view it on GitHub, or unsubscribe.Triage notifications on the go with GitHub Mobile for iOS or Android. You are receiving this because you commented.Message ID: ***@***.***>

[JesseJanssen]

After some Googling I don't know if I can reset that, the only thing I can find is that you can reset the official DTU/connection with a reset button on the DTU but I don't think that will do anything for the inverter... Someone told me AhoyDTU works with channel hopping inverters so I might try that and keep an eye on OpenDTUs updates, I will keep you posted!

[JesseJanssen]

Just for anyone who is experiencing the same or similar problem(s), with OpenDTU I cannot solve this for now because they don't support channel hopping, I got access to a beta version of AhoyDTU which does support channel hopping and that solved my issue.

[paragdhuri]

I also have HMS 1600 4T and got a lot of partial received, but the PR #2962 worked for me.

[dtakken]

Just for anyone who is experiencing the same or similar problem(s), with OpenDTU I cannot solve this for now because they don't support channel hopping, I got access to a beta version of AhoyDTU which does support channel hopping and that solved my issue.

Does this mean that the HMS-1600-4T is not supported after all? I just installed a solar panel setup with two of these units a couple of days ago, as it was listed as supported... Not much luck so far communicating with either of them. Today I got one successful power reading from one of them.

Some details:

• Communication works fine using the original Hoymiles DTU. Tried that one initially to verify that the inverters are working correctly. Then shut it down and powered the OpenDTU unit.
• DTU is pre-built from blinkyparts
• Using an iPhone charger to power the DTU (2.4A / 12W) and a good quality cable (I think, its's a lot thicker than most USB-C cables I have)
• Flashed the latest firmware to make sure old firmware wasn't the issue
• Placed the OpenDTU fairly close to the inverters, about 2-4 meters. I experimented with various radio power levels. RSSI is about -36dB - -54dB.
• Tried changing the radio frequency band up in small steps from 665 MHz until 667 MHz, made no difference.
• In the logs I see lots of "last missing" / "middle missing" messages.
• The stats show mostly Receive Partial and Receive Nothing RX errors. About 1% is successful. This remains the case, no matter what I try
• Poll interval is 10 seconds.

Any hints on what to try next are appreciated!

[JesseJanssen]

You could try to make sense out of the PR paragdhuri posted but I can't make much out of it, other than that your best bet would be to go into Discord and seek for help there, possibly you would be able to get invited to a beta/test version of AhoyDTU (they are in the same Discord as OpenDTU) which does support inverters with channel hopping. The only downside I could think of is that they told me not all hardware capable of running OpenDTU is also able to run AhoyDTU so it might turn out your DTU isn't compatible.

[paragdhuri]

You can take the code from PR here #2962 and compile it and upload onto Casmo DTU, and it worked! Here are the steps to compile and upload the open DTU code: https://www.opendtu.solar/firmware/compile_vscode/

[ththeimer]

Hi, I would guess that the behaviour of the HMS-1600-4T depends on the inverter firmware version. Since it was installed recently it probably has the latest firmware which may behave differently from earlier versions. It would make sense to also include the inverter firmware release in the compatibility list.Am 20.05.2026 um 19:05 schrieb paragdhuri ***@***.***>:paragdhuri left a comment (tbnobody/OpenDTU#3063) You can take the code from PR here #2962 and compile it and upload onto Casmo DTU, and it worked! Here are the steps to compile and upload the open DTU code: https://www.opendtu.solar/firmware/compile_vscode/ —Reply to this email directly, view it on GitHub, or unsubscribe.Triage notifications on the go with GitHub Mobile for iOS or Android. You are receiving this because you commented.Message ID: ***@***.***>

[dtakken]

You can take the code from PR here #2962 and compile it and upload onto Casmo DTU, and it worked! Here are the steps to compile and upload the open DTU code: https://www.opendtu.solar/firmware/compile_vscode/

@paragdhuri Hmmm... I don't see how that PR is related to HMS-1600-4T?