I recently got a pi and it came with the a DVK511 board a number of other things, such as a LCD1602 screen. I have the custom raspbian image on my SD card that my pi is running, and is currently booted off of. However, after attaching the ribbon cable to the DVK511 and the Pi, the DVK511 has it's lights on, and if I plug the LCD1602 into the correct pins, it's screen lights up a light blue. However, when I 'make' the LCD1602 test program that comes with the waveshare version of Rasbpian, and then run it via LCD1602_Test, nothing happens on the LCD, and a few LEDs on the DVK511 flash. I tested the LEDs to make sure I had the board connected to the raspberry pi correctly, and they worked. Did I do something wrong or is the LCD defective?
Your LCD may actually be working correctly. It may simply be a matter of the contrast being set incorrectly. To correct this turn the knob or screw on the contrast potentiometer. You should try turning it both clockwise and counterclockwise. Ideally you can do this while the Pi is sending text to you display, but depending on its position this may not be possible. In this case adjust the screw in one direction and test. If that fails try turning the screw in the opposite direction and retest.
I have recently got this kit (DVK511) and was able to get the 1602 working after a little testing with the potentiometer but as another user here, even at max it's barely legible. I'd like to test if it just needs extra power via the 5v DC plug but I haven't found any information as to what polarity or max amp and I'd hate to kill the thing. WaveShare was nice and sent me this site for any/all information they have including software and source code. Should I worry about polarity or just throw in any old 5v adapter... If you'd like my source code for writing on the LCD, I might put it on my github later.
Maybe your test code is not correct. Today I've used wiringPi library and succussfully light up the LCD1602 and show tempreature on it. DVK511 use the GPIO ports like the following: GND 3.3V V0 IO3 GND SCK X X X X IO4 MOSI MISO IO6 3.3V GND It uses 4 bits mode so that wiringPi's library function lcdInit() should be called like this: lcdInit(2,16,4,3,14,4,12,13,6,0,1,2,5); 2--2 rows 16--16 cols 4--4 bits mode 3--LCD1602's RS is controlled by wiringPi's GPIO3 14--LCD1602's RW is controlled by wiringPi's SCLK 4,12,13,6--LCD1602's DATA (4 bits mode) is from IO4,MOSI,MISO,IO6 the last 4 ports which not duplicate with the former 6 ports should be all right. I don't know what library you use, but the problem could be the same