Hey everyone, just wanted to make a quick note that after several days of testing, I can confirm that the FT-5 (R1) works just fine on the Marlin 1.1.8 firmware, the latest version available, which was released on Dec 31, 2017. I couldn't find any other discussions about firmware updates beyond the factory image on the forum here, so I thought it was worth mentioning my working setup in case anyone else was considering an update.
The "official" FT-5 firmware from the Google Drive location is Marlin 1.1.3, which was released June 4, 2017. For some reason the file archive is titled
... and the Configuration.h file has the machine name manually set to "FT-5 Marlin 1.1.2", so that is what will display on the LCD. But the Version.h file inside the archive identifies it as the 1.1.3 codebase. So I suspect there was a partial copy/paste upgrade from 1.1.2 to 1.1.3 at Folgertech at some point.
"FIRMWARE Marlin_v1_1_2_ R1R2ft5_stock.zip"
There were a ton of changes and bug fixes between the 1.1.3 and 1.1.8 versions. I gather that there was a planned "feature freeze" at one point for the 1.1.x branch in favor of improving the upcoming 2.0.x branch, but it looks like the 1.1.x floodgates opened again for Marlin 1.1.7 when 2.0.x wasn't yet ready.
More info in the Marlin release notes:
For me, the fact that the menu on the LCD can now scroll long filenames when printing from SD cards makes it worth the upgrade for that feature alone.
There are a considerable number of differences between the Configuration.h files from the FT-5 1.1.3 Marlin and the generic 1.1.8 Marlin. I wouldn't recommend using your old file since so much has changed, and I certainly wouldn't try running the unmodified 1.1.8, as the endstop logic and other mechanical/electrical parameters are not correct. What I did, which worked well, was to open up both the old and new files in a graphical diff/compare utility and manually edit the new file to capture the FT-5 specific configuration options which were applicable, editing them as necessary when the formatting or layout changed... ie, looking at what the changes meant to a section, not just a line-by-line diff since they didn't always correspond due to the changes.
So yes... it works. I thought I had a PID auto-tuning issue at one point, but it's been holding temps pretty well with the values the auto-tune gave me. So no complaints, seems to work just fine.