New Oscilliscope Part 3 – Screen Capture

With the TDS544A up and running, I decided to take a crack at getting data off of it. The scope has a floppy drive (but my laptop doesn’t), a GPIB port, and a printer card with both parallel and serial interfaces. The hardcopy menu has around 18 options for filetypes, and is capable of sending the screenshot to any of the ports or the floppy drive.

Of the options available, I decided to try sending a windows BMP file over the serial port. I used a F-F null modem cable and a USB to Serial converter. On the program side, I started with this autohotkey script which spews data from your serial port into notepad. With a little bit of munging (removing anything to do with sending data, and removing some of the ASCII conversion logic), I was able to get and write BMP files. A full 640×480 color bitmap takes about 90 seconds to transfer (max speed 19200), but the scope provides a compressed BMP (Run Length Encoded) that is quite a bit smaller. These screenshots are from the script, and are of the scope measuring the 1kHz calibration signal from the front panel.

TDS544A 2013-07-12 090642 This second shot shows how fast this scope is. Same signal, but here we can measure the ringing of the calibration signal. (Look at the time scale).

TDS544A 2013-07-12 090825For reference, here is the script (without much cleanup): Serial Image Receive.ahk. It does depend on the RS232 library functions linked to above.

The only issue now is that the scope seems to forget some piece of data on reboot. It may be an NVRAM issue, or just me abusing how the system works, but I need to go to the utility menu and toggle the serial settings to get the scope to transmit.

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