On Thu, 22 Oct 2015 17:48:01 -0700 (PDT), you wrote: >Hello, > >I purchased a SainSmart LCD2004, which I believe is a hd44780 LCD with an >i2c module pre-soldered to the back of the board. This board is designed >for an Arduino, but I wanted to try using it on my Beaglebone. Is this >doomed to fail?
Not necessarily so. It depends on what the I2C module is. You will need to know what the I2C commands to the module happen to be, that is one thing. The known commands for the 44780 are likely to be easy to get. The module I don't know anything about. > >Following a few online guides, I have the SDA and SDL pins, as well as the >5v and ground pins attached (with a resistor). I've tried endless python >scripts and libraries, being careful to configure each to use the addresses >that i2cdetect is showing. Upon running some of the scripts, the LCD >actually blinks. I tried to go the LCDd route, but no luck with that >either. The LCD backlight goes on, but no text. The backlight goes on most likely because there's 5 volts on the display. The uninitialized display shows a sequence of square blocks on line 1 (and nothing on line 2). The SDA and SCL pins need to go to 5 volts through a resistor (each line independently). The resistor values are generally between about 4.7K and 10K. What I don't know (and you need to check) is whether or not the BBB's I2C system runs from 3.3 volts or 5.0 volts. If 5.0 volts AND the LCD display I2C runs from 5 volts, then you can connect them directly. If the LCD and BBB run on 3.3 volts (for the interface), then they can be connected directly. IF they are not the same, then you need a chip (I'd recommend the PCA9517) to connect the two. This chip allows dealing with different supply voltages (such as 3.3 and 5.0). I use this chip in systems I design. Typically, the processor I/O is at 3.3 volts (even the I2C pins), and the system level is 5.0 volts. Thus, I need a chip on each board to the system interface. For a 5.0 volt system, I still use the chip because it provides isolation (there's a limit on current, cable length (related to capacitive loading) and capacitive loading on each driver; check the specs.) You might want to look at these issues, they're reasonably easy to fix. Harvey > >If I'm in the wrong Forum, or missing something simple, let me know. I >can expand on anything that I've tried. > >A little background - I'm a competent Linux user, so running tools and >banging together scripts is the easy part for me. The connecting the >electronic components has been the learning part of this journey. > >Many thanks. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
