I2C LED matrix on the Raspberry Pi
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I2C LED matrix on the Raspberry Pi

by rpural on Mon Jul 30, 2012 10:48 am

Since the example code for the LED matrix seems to be for the Ardunio only, is there any documentation of the I2C protocol to drive the 902 bi-color 8x8 bi-color LED matrix?

Or, is there documentation on where the Wire.h library can be found? This is the first stumbling block to compiling the code on the Raspberry Pi....
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Re: I2C LED matrix on the Raspberry Pi

by adafruit on Mon Jul 30, 2012 11:27 am

its just not that simple - the wheezy distribution doesn't even have i2c enabled on it, and arduino code wont compile on a linux machine. we may have example code at some point, but there is no ETA!
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Re: I2C LED matrix on the Raspberry Pi

by rpural on Mon Jul 30, 2012 2:49 pm

Actually, I2C support is compiled into the Wheezy kernel, but is blacklisted in the boot, as it isn't needed by the normal user. Removing that blacklist entry, and adding a modprobe for i2c-dev will create the /dev/i2c-0 device. Installing i2c-tools provides a high-level view of the I2C interface.

The command sudo i2cdetect 0 will show the 8x8 matrix attached to the system as device x'70'. I just have no idea how to use /dev/i2c-0 from that point to use the display. Actual documentation for the I2C Backpack and its supported command structure would go a long way to making the device usable on the Raspberry Pi. At this point it is not an electronic problem, just one of documentation.
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Re: I2C LED matrix on the Raspberry Pi

by adafruit on Mon Jul 30, 2012 2:57 pm

feel free to experiment and try porting it but its just not as simple as 'copy and pasting' - arduino code wont compile on a linux machine. we may have example code at some point, but there is no ETA!
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Re: I2C LED matrix on the Raspberry Pi

by rpural on Mon Jul 30, 2012 5:01 pm

You've missed my point; Don't write sample code. Document your interface.
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Re: I2C LED matrix on the Raspberry Pi

by adafruit on Mon Jul 30, 2012 5:32 pm

The entire interface is completely documented in the HT16K33 datasheet - the backpacks only use that chip, it handles all the LED functions :)
Please check http://learn.adafruit.com/adafruit-led- ... /downloads for the datasheet, it has detailed interface information!
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