GroG
October 28, 2013, 2:57pm
1
Hello !
I have decided to jump into I2C after dragging my feet for a couple years..
My question revolves around wanting to get 24+ 7 Segment LED drivers (http://www.adafruit.com/products/879#Description ) on the same I2C bus..
As far as I can tell I2C (from a RasPi) supports 7 bit addresses .... 128 devices WOOHOOOO !
But this doohicky has only 3 soldering bits ! NOOOOO! I was thinking… hey, mebbe Adafruit decided it was just not roomy enough to have 7 sodering pads … and if I look hard enough I can solder or short pins so that I can get all 7 bits … http://www.adafruit.com/datasheets/ht16K33v110.pdf
I see that the chip “hardwires” the other address bits … NOOOOOOOOO!
My questions are :
Is this common practice… I’ve heard of “base address” fron I2C device manufacturers … doesn’t this (like this case) whipe out a bunch of addresses !!! Is there any way around this ? Is there any slave device that is nice enough to give us all 7 bits ??!? WHATS GOING ON !?!?
Most devices have just a few addresses based off a base address.
Most i2c devices have just a few addresses based off a base address. You may find some that have them all though.
Programmable things like uC have it where you can choose more adreeses.
GroG
October 29, 2013, 9:13am
3
Thanks for all your input
Found this
http://forum.arduino.cc/index.php?topic=50930.0 )
Which seemed like a feasible work-around … although it does require more chips & salsa
Maybe
https://learn.sparkfun.com/tutorials/using-the-serial-7-segment-display It uses an arduino to address the 7 segment pins and brings out the i2c lines, plus, it gives you the ability to change the address. https://www.sparkfun.com/products/11441
I see that Maxim has an SPI 8 digit controller. Add a single line controlled shift register, http://www.edn.com/design/systems-design/4410875/One-I-O-line-drives-shift-register-with-strobe , and you can control up to 8 more sets of 8 with a single shift register and only 3 lines.
GroG
October 29, 2013, 2:27pm
5
Thanks Birdmun !
Good find … and just a couple dollars more than Adafruits… But with an onboard ATMega328 and FTDI header…
Admittedly, more chips and salsa are required for that.