Floppy Emu uses a generic LCD that’s a clone of the display in the Nokia 5110 phone. It’s a nice little bitmapped display with a good range of configuration options, including the ability to set the display’s contrast level through software instead of with an external resistor. Unfortunately there’s a huge variability in contrast response from one LCD to the next, and even the same LCD can exhibit contrast changes from day to day. I’m not sure if it’s due to temperature, fluctuating voltages, bad solder joints, or something else, but it makes it virtually impossible to choose one contrast level in the Floppy Emu firmware that will work well for all LCDs. Until now, I’ve been making a custom firmware build for each Floppy Emu that I assemble, with a hand-tweaked contrast level, but that’s a huge pain in the butt. No more!

Firmware 1.0L F11 introduces the ability to adjust the contrast level and save it to EEPROM. Now you can tune the contrast exactly how you like it. To adjust the contrast, hold down the SELECT and NEXT buttons while Floppy Emu is initializing (after pressing the reset button, or when first powering it on). After a few seconds, the contrast adjustment screen will appear. Press PREV and NEXT to tune the contrast level, and SELECT to save the contrast setting to EEPROM. Easy peasy lemon squeezy.

To apply this firmware update to your Floppy Emu hardware, download the firmware files, and copy the file femu.bin to your SD card. Then hold down PREV and SELECT while the Floppy Emu is initializing. This update only changes the AVR software (from 1.0K to 1.0L), the CPLD is unchanged (it’s still F11).

Happy contrasting!