Products > Test Equipment

MHS-5200A Serial Protocol Reverse Engineered

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lcltech:

--- Quote from: Muxr on June 28, 2015, 06:26:04 am ---Nice, I should give this a try on my MHS-3225. Wonder if they are compatible. Just re-read your first post, and noticed the protocol is different.

--- End quote ---

Does anybody know what else is the difference between MHS-3200A and MHS-5200A? The specs are exactly the same.

janoc:

--- Quote from: free_electron on July 02, 2015, 10:00:06 am ---Teardown !

--- End quote ---

I have received my 25MHz unit and it is pretty much the same as in the photo. The architecture seems to be an STM8 micro (small TQFP on the right) handling the coms & display, CH340G (upper right TSOP) usb uart bridge deals with the USB part. The signals are produced by a Lattice MachXO2 CPLD/FPGA (large QFT in the center) with 2 8bit resistor DACs (left of it) with some opamps (immediately left of the DAC ladders) and AD603ARs (left from the opams). I didn't remove the heatsink, so not sure what is under it - perhaps some power transistors.

The rest is not very interesting - there are relays to switch the outputs on and off, standard 2 line LCD, encoder knob on a separate board and a boatload of passives. The bottom right of the board is a switching PSU.

It looks fairly well built, actually, especially for the price. I have seen much much worse already.

However, what I would love to get is an English manual. The original is in Chinese, unfortunately. I still haven't figured how to actually use the counter functionality the unit is supposed to have nor how to use the various synchronization inputs, including the TTL inputs and outputs on header in the back.



--- Quote from: Polossatik on July 02, 2015, 08:43:08 am ---the specs I found on ebay list only higher than 6MHz for “sine wave” in the 3 “top” models (12/20/25 MHz),
all other wave forms are speced at 6MHz

Care to open up and have a look if the difference is pure in firmware or they add in the more expensive ones some kind of additional ( hardware?) sine wave generator.
? :)

--- End quote ---

There isn't any separate gen for 25MHz and 6MHz square wave. I have checked the signal on my scope and when set to square wave, the signal starts getting distorted around 1-2MHz and the higher you go, the more sine-like it looks, until you get basically straight sine wave above around 4-5MHz (it might do 6MHz, but I didn't probe it correctly). On the scope it looks like as if there was a heavy low pass filter and the higher harmonics were getting progressively cut from the signal as the frequency was increased. Not sure whether there is a physical low pass filter on the output or whether it is an artifact of the sampling.







janoc:

--- Quote from: wd5gnr on June 28, 2015, 04:23:07 pm ---If you can't stand not having a GUI, I found the TTI Waveform Manager Plus runs well under Wine and is free to download (registration required). If you export to "normalized" you can import to the MHS5200A by using the -f flag to the software I provide.

--- End quote ---

Thanks for this, that software is really pretty good. I have tried your scripts to upload the waveforms to the generator and hats off to your shell scripting :-p

I would probably rather do it using Python or something like that though, shell/awk isn't the best choice for this type of job, not to mention that Python is a bit more portable than the above combo.

BTW, a pro tip for anyone using this generator - record a waveform with a scope, save as CSV, open it using Waveman, clean up and upload to the generator. Bingo, signal reproduced for debugging stuff. Works like a charm!

wd5gnr:
I don't have an English manual, but I've worked it all out. You probably figured that what the main buttons do (pgup/dn for the menu). For the counter on the menu look for:

MSR-Sel. Press OK to go external or TTL.
MSR-Mode. Press Ok to select frequency/count/pos pulse width/neg pulse width/period/duty cycle
Gate-Time. Freqency gate


One of the menu items changes depending on your MSR-Mode (the one after Gate time). If it says C it is reading counts.pressing ok pauses. If it says F it is reading frequency. You can probably figure the rest out from there.

wd5gnr:
I'm not a big Python fan, but the script works well and with Cygwin actually that is a pretty portable combo too ;-)

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