Ah, if you are referring to a logic level converter, I had ordered one but wasn't sure if that was what I needed. I'll read more on how to use it, and try that. Thank you.
On Thu, Oct 22, 2015 at 9:12 PM, Harvey White <[email protected]> wrote: > 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 a topic in the > Google Groups "BeagleBoard" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/beagleboard/4LoTzFAwzxg/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- 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.
