Remote control of HP33120A, lessons learned

[BritishGas]

Hello everyone,

Just a quick post which will hopefully point you in the right direction if you want to control your HP 33120A 15MHz function generator remotely.

I am communicating with the instrument via the RS232 interface. In order for this to work you must:

1) Use a suitable USB-serial converter. I initially used the UGREEN 20210 converter with a Prolific PL2303 chipset. This claims "automatic" hardware flow control however I was unable to connect to the instrument at all with flow control enabled in device manager. Uploading arb waveform data without the flow control enabled could only take place at very low data rates (<<9600 baud), otherwise the instruments input buffer would overflow. I probed the DTR line at 9600 baud and you could see the instrument desperately asking for the data to stop. A request duly ignored by the converter.

Changing to a converter with FTDI chipset made these woes dissapear, the hardware flow control is also "automatic", but it actually works! This is the cable I used:

StarTech.com ICUSB2321F

https://www.amazon.co.uk/gp/product/B004ZMYTYC/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1


2) Use a Null modem cable to swap pins 2/3, 4/6, 7/8. The particular cable I used was:

StarTech.com SCNM9FF1MBK 1m Black DB9 RS232 Serial Null Modem Cable

https://www.amazon.co.uk/gp/product/B00QM8ZP5E/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1


3) Send data to the instrument. The "Intuilink" arb waveform software is still available for download from the keysight website.:

https://www.keysight.com/main/software.jspx?ckey=1000000918%3Aepsg%3Asud&lc=eng&cc=GB&nid=-536902324.536881979&id=1000000918%3Aepsg%3Asud

Although this remains a useful tool for creating waveforms and exporting as csv, it was unable to see the device over RS232. Instead I wrote a small python script using the pyvisa library (if you don't want to do this, the "Dump file to port" feature of the RealTerm emulator is an easy way of sending csv data to the device).
I've attached the python script in case it is useful for others.

Let me know if you have any questions.
Thanks,
Gerry

[GreyWoolfe]

I have the same Startech cable.  My last 2 company laptops didn't have a serial port and it worked well for the serial devices we had deployed in the field at the time.  I don't recall any need to play with settings, it was just plug and play.  Now everything is USB but I still have the cable.  Never know when I will need it.

[BritishGas]

The Startech cable works brilliantly, it was the UGREEN cable with Prolific chipset which was a pain