Dell's Linux support for this printer is limited to a
.ppd file that hasn't been updated since 2015, and that doesn't support the manual duplex mode that is apparently hard-coded into the printer's firmware.
To elucidate, when printing under Windows with provided drivers the user can set duplex options normally (
one-sided, long-edge, short-edge), and then the printer's lcd display prompts the user to manually put the pages back into the paper tray after half the job is complete (and press the
Okay button to finish the job). This suggests that the manual duplex feature is baked into the printer's firmware, as it doesn't require the user to do anything on the client computer after the initial job is sent. Driver
.ppd file in the Windows driver has the expected lines about configuring a print job for duplex printing, so one would expect that the printer firmware "knows" how to handle duplex jobs despite lacking a duplexer. Linux
.ppd file for E525w does not have the lines for setting duplex options, and thus by default the only duplex option available when printing under Linux is
Just for giggles I used
dos2unix to edit the Windows
.ppd file and make it compatible with
cups under Linux Mint (see attached file). As expected, duplex options were now available when configuring a print job. However, when a duplex job is sent to the printer from Linux, it comes out as
one-sided, without the printer display prompting the user to put pages back into the tray. I also tried
lp sides=two-sided-long-edge, same result. In addition to the default Windows driver, I also modified the Dell "Open Print" driver that's supposed to be widely compatible with all of Dell's Laser/LED printers with embedded print servers, same result.
Granted, manual duplex works in Windows just fine, so this is primarily an academic exercise. If I were to guess, this printer has some sort of custom flag that's sent to the print server from the Windows driver, but I don't have any way to verify. Short of reverse-engineering the firmware I don't know what else to change in the
.ppd driver. I'll continue to update this question as I try more stuff, but I'm open to any other suggestions from anybody bored enough to help.
Here's the Open Print Driver (OPD), modified to work with