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Looking for recommendation on driving multiple serial displays


#1

Hello all,

Do any of you good folks have experience driving multiple serial displays from a single board? I need to drive 8 serial displays from a FEZ Cobra II Eco and have yet to figure out the best approach.

Thanks much,
Larry Scott
:smiley:


#2

Depends on displays. Do you have specification?


#3

Thanks for the quick reply!

Here is a link to the display I am working with:

http://www.newhavendisplay.com/nhd0220d3znswbbwv3-p-5743.html?zenid=2qhpukeo1i210pp2keul3ehs41

I see the Cobra II Eco has 5 UARTS, 3 I2C, and SPI capability…

I believe SPI (or I2C) allows for daisy chaining serial devices and maybe that is the approach I need to take.

Just looking for any info on how somebody else may have approached the problem.

Thanks again!


#4

Definitely use SPI. Looks like combined the will need ~300mA, so you can supply the power from Cobra’s 5v, but double check that.


#5

Not sure of your application for needing all those displays - you should share that if you can because it sounds interesting.

SPI is relatively simple - you need a chip select line per device, and the rest of the signals are a common bus. This means you need to instruct devices individually - do one, move onto the next. There’s relatively few SPI channels on a typical micro, but the limiting factor is more likely to be the separate chip select lines.

I2C is relatively simple - you just need the I2C bus lines shared, and it uses a device address sent on the bus to communicate to a specific device. You may find that it’s a challenge because you need to be able to de-duplicate the addresses on the shared bus - according to the data sheet, your display apparently can be configured to use any device ID so that’s not overly a concern (but you must remember to do that). There are typically very few I2C channels on a micro (perhaps only 1) but you can also de-duplicate things using software I2C (which may get you away from having to redefine hardware addresses and the like).

UART is also simple but not shared. UARTs are limited resources, and depending on the speed needed can be more taxing on processor speed (in receive scenarios, so probably not really a factor for you). If you needed to move to more displays for some reason, then you’re likely to have exhausted the available UARTs

If this was my project I’d probably choose SPI. I2C would be my second choice and I’d aim to use individual Software I2C setup per display rather than re-mapping addresses in the hardware, it makes substituting a failed device easy. UART would probably be my last choice.


#6

Thanks guys! Excellent feedback.

I plan to start on the project in the next few months.

I will try to post the results when complete.