HL2 to Xiegu's XPA125b Interface with remote control capability

[KP4RX - Ramon]

Hello my fellow Hams and HL2 enthusiasts! I've built an Interface for Hermes Lite 2 to XPA125b amplifier which allows for remote control. This is the first iteration and I'm pretty sure that improvements can be done, but for now it does the job for me and I hope that is useful for someone else out there. The remote functionality requires minor modification to the XPA Amplifier but in my opinion well worth it. Jim's I/O Board will render this device useless but it's still a nice project to tinker with. My goal is to be able to adapt it to Jim's board in the near future by replacing the Pico for a Pico W to gain Wi-Fi functionality. Suggestions are welcome and If this turns out to be useful for you please let me know! Here's the github repository if you want to check it out: https://github.com/kp4rx/hl2-xpa125b

73 de KP4RX - Ramon

[Reid Campbell]

Hi Ramon,

Thanks for posting your project. I'm hoping to use the I/O Board to interface to my XPA125B and it's useful to know the interfacing details. I'm primarily interested in initiating the ATU tuning cycle but would also like to know when it ends to feed this back to Thetis. I suspect I will just have to use a fixed timer but would be interested if you have any ideas based on your design.

Cheers 

Reid
Gi8TME/Mi0BOT

On 31/08/2023 07:13, KP4RX - Ramon wrote:

Hello my fellow Hams and HL2 enthusiasts! I've built an Interface for Hermes Lite 2 to XPA125b amplifier which allows for remote control. This is the first iteration and I'm pretty sure that improvements can be done, but for now it does the job for me and I hope that is useful for someone else out there. The remote functionality requires minor modification to the XPA Amplifier but in my opinion well worth it. Jim's I/O Board will render this device useless but it's still a nice project to tinker with. My goal is to be able to adapt it to Jim's board in the near future by replacing the Pico for a Pico W to gain Wi-Fi functionality. Suggestions are welcome and If this turns out to be useful for you please let me know! Here's the github repository if you want to check it out: https://github.com/kp4rx/hl2-xpa125b

73 de KP4RX - Ramon

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[KP4RX - Ramon]

Hi Reid,

First of all, I want to thank you for all the time and effort you've invested into enhancing and customizing Thetis for the HL2!

I'm steering my efforts based on a schematic I got from the Xiegu XPA125B Amp Group on FaceBook (Which I'm attaching here for reference). Because the MCU on the XPA is an STM32 I'm not expecting voltages higher than 3.3v when tapping it so that's a good Start. I have to do a little investigation with the multimeter to confirm my theories but so far; for PA and ATU State I'm planning on getting the PA state from MCU Pin 30 labeled PA_ISEN or 36 PA_PEN and for ATU state the base signal of the transistor labeled ATU_EN (Q4 or Q6?) also there's a relay that enables the ATU from what I understand (Trace LATU_EN). For system power state I still need to figure out, but that one seems way easier (Maybe tracing PWR_EN or even lcd Backlight).

Now to your primary interest, for the Tune Routine here's my plan: Turn off the PA, enable PTT, tune, and when tune is completed, re-enable the PA. To consider tuning completed I have four possible plans of action in mind:

1. A timer like you stated (with my antenna, tuning time is variable depending on band, weather, and God knows what else, so not sure if that's the right way for my use case).
2. Now, for a more elaborate approach I'm focusing on the behavior of a board point labeled Tune between C177 and an unlabeled transistor in the schematic connected to Q1, I have a gut feeling that it has to do with tuning routine, if it stays on during cycle then we've hit jackpot.
3. Calculate or average SWR from PWR_FWD and PWR_REV pins and if the SWR is lower than 2:1 then assume the tuning cycle is completed.
4. The most elaborate approach and maybe beyond my current skills, tap into the i2C buses and analyze what (If something) happens during tuning cycle.
5. While writing this I thought, maybe scrub the LCD data to read SWR, but again, way beyond my skills and seems messier.

I'm learning in the process, maybe one of these approaches is feasible, maybe none of them will work, but I'm willing to try. If you or someone else has another idea please let me know. My main goal is to have the ability to setup a fully functional hardware combination back home in Puerto Rico with the HL2 to operate it in all modes remotely from my TX QTH or anywhere in the world, also my "remote" HL2 in the garage! LOL. Currently I have a Remote QRP Station in PR for Digital modes, but SSB is something that I'm missing there. BTW, I'm planning to test your Thetis VPN enhancements with a WireGuard VPN as soon as I have some spare time.

There are coupe of hardware versions for the XPA125b in the wild, but I'm mostly certain that if one of these options work it is just a matter of identifying the right taps on different hardware versions.

Best Regards!

Ramon - KP4RX

[Reid Campbell]

Hi Ramon,

Thanks for posting the circuit for the amp, that has been very informative. I was frustrated that Xiegu's FCC submission excluded the circuit diagrams.

It's interesting that there is provision for a fan but it's not used in the final design. It would be interesting to see what those controls do.

On 01/09/2023 03:45, KP4RX - Ramon wrote:

Hi Reid,

First of all, I want to thank you for all the time and effort you've invested into enhancing and customizing Thetis for the HL2!

I'm steering my efforts based on a schematic I got from the Xiegu XPA125B Amp Group on FaceBook (Which I'm attaching here for reference). Because the MCU on the XPA is an STM32 I'm not expecting voltages higher than 3.3v when tapping it so that's a good Start. I have to do a little investigation with the multimeter to confirm my theories but so far; for PA and ATU State I'm planning on getting the PA state from MCU Pin 30 labeled PA_ISEN or 36 PA_PEN and for ATU state the base signal of the transistor labeled ATU_EN (Q4 or Q6?) also there's a relay that enables the ATU from what I understand (Trace LATU_EN). For system power state I still need to figure out, but that one seems way easier (Maybe tracing PWR_EN or even lcd Backlight).

Now to your primary interest, for the Tune Routine here's my plan: Turn off the PA, enable PTT, tune, and when tune is completed, re-enable the PA. To consider tuning completed I have four possible plans of action in mind:

1. A timer like you stated (with my antenna, tuning time is variable depending on band, weather, and God knows what else, so not sure if that's the right way for my use case).
2. Now, for a more elaborate approach I'm focusing on the behavior of a board point labeled Tune between C177 and an unlabeled transistor in the schematic connected to Q1, I have a gut feeling that it has to do with tuning routine, if it stays on during cycle then we've hit jackpot.

That's what I was wondering.

Do you have a scope or are you just running with a meter? I picked up a FNIRSI DPOX180H on Banggood for about $130. It's a 2 channel 180MHz hand held scope. Now I haven't used it that much but I'm happy with it for that money.

The other piece of cheap test equipment I got was a generic 8 channel logic analysers which runs with the Sigrok software. I have been using it to watch the I2C channel on the I/O Board. They are around $10-$20 depending on the leads you get with it.

1. Calculate or average SWR from PWR_FWD and PWR_REV pins and if the SWR is lower than 2:1 then assume the tuning cycle is completed.
2. The most elaborate approach and maybe beyond my current skills, tap into the i2C buses and analyze what (If something) happens during tuning cycle.
3. While writing this I thought, maybe scrub the LCD data to read SWR, but again, way beyond my skills and seems messier.

I'm learning in the process, maybe one of these approaches is feasible, maybe none of them will work, but I'm willing to try. If you or someone else has another idea please let me know. My main goal is to have the ability to setup a fully functional hardware combination back home in Puerto Rico with the HL2 to operate it in all modes remotely from my TX QTH or anywhere in the world, also my "remote" HL2 in the garage! LOL. Currently I have a Remote QRP Station in PR for Digital modes, but SSB is something that I'm missing there. BTW, I'm planning to test your Thetis VPN enhancements with a WireGuard VPN as soon as I have some spare time.

There are coupe of hardware versions for the XPA125b in the wild, but I'm mostly certain that if one of these options work it is just a matter of identifying the right taps on different hardware versions.

I think I have one of the older models as I bought it in 2020. I think, in your pictures, there are small RF connectors connected to the UHF sockets on the back panel. If I remember correctly, mine are just coax soldered to the connectors. I'm impressed with the internal construction of the XPA125B, it's quite professional.

I congratulate you on your efforts and I must have a look at the Facebook pages.

Cheers 

Reid
Gi8TME/Mi0BOT

Best Regards!

Ramon - KP4RX

On Thursday, August 31, 2023 at 3:17:01 PM UTC-5 scumballc...@gmail.com wrote:

Hi Ramon,

Thanks for posting your project. I'm hoping to use the I/O Board to interface to my XPA125B and it's useful to know the interfacing details. I'm primarily interested in initiating the ATU tuning cycle but would also like to know when it ends to feed this back to Thetis. I suspect I will just have to use a fixed timer but would be interested if you have any ideas based on your design.

Cheers 

Reid
Gi8TME/Mi0BOT

On 31/08/2023 07:13, KP4RX - Ramon wrote:

Hello my fellow Hams and HL2 enthusiasts! I've built an Interface for Hermes Lite 2 to XPA125b amplifier which allows for remote control. This is the first iteration and I'm pretty sure that improvements can be done, but for now it does the job for me and I hope that is useful for someone else out there. The remote functionality requires minor modification to the XPA Amplifier but in my opinion well worth it. Jim's I/O Board will render this device useless but it's still a nice project to tinker with. My goal is to be able to adapt it to Jim's board in the near future by replacing the Pico for a Pico W to gain Wi-Fi functionality. Suggestions are welcome and If this turns out to be useful for you please let me know! Here's the github repository if you want to check it out: https://github.com/kp4rx/hl2-xpa125b

73 de KP4RX - Ramon

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[KP4RX - Ramon]

Reid, yes, I'm working only with a multimeter. I've pulled the trigger and ordered that logic analyzer and the oscilloscope, I'll try to work on understanding the logic analyzer concept this weekend. Thanks for the recommendation!, I'm sure both tools can be useful for many other projects, even working on the CW Keyer Steve sent couple weeks ago.

As for the Amp, my board says All In One V 1.04, it is a warranty replacement from the original design from 2020 which died close to the warranty expiration because of a bad firmware update. Honestly the original one was less susceptive to over drive and tuning was quicker but that may be just perception. Nevertheless still a great Amp!

Regards,

Ramon - KP4RX