how to control LTDZ MAX2870 23.5-6000Mhz signal source?

[biastee]

I bought a "LTDZ MAX2870 23.5-6000Mhz signal source" (attached image), which is available from all the major online platforms.  However it didn't come with any instruction.

There are 5 tact switches on the PCB, covering the following functions: <, >, ^, v, and OK. I can change the frequency thru these switches, but for the life of me, I can't figure out how to manually change the amplitude. In the attached photo, the amplitude is displayed on the bottom row of the display.

There is a frequency sweep function, but I can't figure how to start the sweep.

According to the advertisement, the item can be PC controlled, but no software is provided. When I tried to connect with the MAX287X PLL EV Kit Software, it couldn't detect the signal source (error message in attached image below).

Thanks.

[ledtester]

A couple of things...

Banggood sells the same device:

https://www.banggood.com/Geekcreit-LTDZ-MAX2870-STM32-23_5-6000Mhz-Signal-Source-Module-USB-5V-Power-Frequency-and-Sweep-Modes-p-1696744.html

and if you follow the link >>>Instruction: Click here to open<<< it brings you to this low-level protocol documentation:

http://myosuploads3.banggood.com/products/20200618/20200618202558MAX2870STM32RF.pdf

Also, Tony Albus has both the ADF4351 and MAX2870 versions, and in this video he shows the same control program operating both the ADF4351 and MAX2871 (at time 21:29):

#129 MAX2870 LCD Signal Generator vs ADF4351 LCD Review Teardown -- Tony Albus
https://youtu.be/DFtC7icVr-E&t=21m29s

and he thanks the ebay store "pincei_de" for the control software:



Tony is also on this forum (username "tonyalbus"), so you might contact him.

The MAX2870 and ADF4350 are very similar -- here's a Maxim app note comparing the register layout in both devices:

App Note 5498 - Comparing the Registers and Loop Filter of the MAX2870 and ADF4350 Synthesizers
https://pdfserv.maximintegrated.com/en/an/AN5498.pdf

[ledtester]

Here is some more info which may be of interest...

This is a very comprehensive video on a particular ADF4351 module and one thing it does is it explains how the Analog Devices eval board and software interact with each other:

[005] 4.4GHz RF Synthesizer Board - ADF4351 - Theory, Setup, Reverse Engineering, Experiments -- OpenTechLab
https://youtu.be/xJ0Mfuj0KUQ

By reverse engineering the eval board and software the author was able to write a python library to control any ADF4351 from a PC. You still need a way for the PC to send SPI commands to the ADF4351 and the python library has code which interfaces with a Bus Pirate USB device for this purpose.

The python library may be found here:

https://github.com/jhol/pyadf435x

The main thing this library has is the logic which figures out what the ADF4351 control register values should be to generate a particular output frequency.

[richard.cs]

When I tried to connect with the MAX287X PLL EV Kit Software, it couldn't detect the signal source

I have used the official eval kit at work recently. It has a PIC on the board that pretends to be a USB-HID, and forwards raw register contents on to the synth. The protocol for this USB HID is entirely undocumented but fairly straightforward to reverse-engineer.

I suspect these cheap modules have a totally different interface.

[bb1]

Banggood document gives wrong Serial port speed. Correct speed is 9600.
Unfortunately, after sending PC commands to the (max2870 board with OLED display) by PC virtual com port, the STM controller cannot stop trying to setup max2870.
For example, if 100 MHz frequency setup was sent, after that the STM every 100 mS repeats sending the the setup of 100 MHz to max2870.
When max2870 gets the setup data from the STM, it starts search of the correct frequency bank.  It does not understand that the correct frequency is already set.
During several hundred microseconds max2870 outputs a lot of different frequencies, including, for example, 140 MHz, while it finally returns to the same 100 Mhz output. This behavior can be fixed by sending wrong serial port command, for example, changing second byte to 0xaa instead if 0x55.

[bg]

Hi ,

I'm writing an open source for this board (Linux / macOS ), you can find the source docs here:

https://github.com/gbonacini/sigenmax2870

the software permits to set frequency and gain by command line, because the documentation I found on-line lack of details about the advanced functionalities of that board, if you have more detailed documentation don't hesitate to contact me, I'm available to add the missing features. I'll add  a GUI soon, check my GitHub page.

[horo]

A little bit off-topic - regarding the ADF4351 EVAL BOARD:

The python library may be found here:

https://github.com/jhol/pyadf435x

The main thing this library has is the logic which figures out what the ADF4351 control register values should be to generate a particular output frequency.

I forked jhol's project for the ADF4351 eval board to improve the firmware (read back lock status, add persistence that allows to use the eval board without PC connection as a fixed frequency source) and add some more features, e.g. a GUI to set most of the parameters.

https://github.com/Ho-Ro/adf435x

[radiolistener]

you can try this one, I designed it for NWT7 and classic LTDZ with ADF4351, but it probably can work with other device types.