This is a library intended to drive the Sure Electronics series of LCD displays. Currently it will successfully drive a DE-LD023 device, but I suspect it should work for the DE-LD021. too. It ought to detect the available device features.
It uses waf as the build system. To install:
./waf configure
./waf build
./waf install # as root, probably
There is an example program in sureelec_test.c which prints some system information to the device. This will be compiled as build/sureelec_test. To run, use a command like:
./build/sureelec_test /dev/ttyUSB0
There's another example in sureelec_test2.c which accepts input using a readline interface, which will then be sent straight to the device. It is run similarly:
./build/sureelec_test2 /dev/ttyUSB0