0.56" seven Segment Backpack Display Pul-up Resistors

Adafruit Ethernet, Motor, Proto, Wave, Datalogger, GPS Shields - etc!

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
User avatar
mboroff
 
Posts: 96
Joined: Sat Feb 22, 2014 7:45 pm

0.56" seven Segment Backpack Display Pul-up Resistors

Post by mboroff »

I have the Adafruit 7-Segment Display that I have used on Uno, Mega2560 and DUE boards by wiring the I2C bus lines. I would now like to use this on anATtiny85. While looking for corrections to the compile I corrected the problem with PCREL I found information that states one should always use a pair of pull-up resistors on an I2C bus. http://www.robot-electronics.co.uk/acat ... orial.html.

My question is "Do I need to put these resistors in my curcuit or are they built into the backpack?

User avatar
adafruit_support_bill
 
Posts: 88093
Joined: Sat Feb 07, 2009 10:11 am

Re: 0.56" seven Segment Backpack Display Pul-up Resistors

Post by adafruit_support_bill »

Pull-ups are built into the backpack.

User avatar
mboroff
 
Posts: 96
Joined: Sat Feb 22, 2014 7:45 pm

Re: 0.56" seven Segment Backpack Display Pul-up Resistors

Post by mboroff »

Thanks. Any reason you can think of when the backpack doesn't show anything using the seven segment example on a Tiny85. It runs fine on the Uno I am using as my ISP programmer also. Blink runs while the programmer is seated on the Uno. I have vcc to pin 8, scl to pin 7, sda to pin 5, and gnd to pin 4. I'm attaching a photo of my boards.
Attachments
tiny85photo.JPG
tiny85photo.JPG (645.81 KiB) Viewed 273 times

User avatar
adafruit_support_bill
 
Posts: 88093
Joined: Sat Feb 07, 2009 10:11 am

Re: 0.56" seven Segment Backpack Display Pul-up Resistors

Post by adafruit_support_bill »

Not familiar with the ATTinyShield, but it looks pretty straightforward. You wiring seems to be OK. You might be seeing some conflict from the UNO pins since the i2c pins on the Tiny are connected to the SPI pins on the UNO. i2c is a tri-state bus and any non-active pins must be set to a high-impedence state, or the bus won't work.

User avatar
mboroff
 
Posts: 96
Joined: Sat Feb 22, 2014 7:45 pm

Re: 0.56" seven Segment Backpack Display Pul-up Resistors

Post by mboroff »

Well this sure stumps me. I took the chip loaded with the code off the programmer shield and put it on a breadboard with it's own power supply. Nothing lights up. Moved the jumpers for the display over to the Uno 5V gnd A4 and A5, which all works well.

User avatar
mboroff
 
Posts: 96
Joined: Sat Feb 22, 2014 7:45 pm

Re: 0.56" seven Segment Backpack Display Pul-up Resistors

Post by mboroff »

Well I just want to add one more piece of information that sort of surprised me. I loaded the code on a ATtiny 84 and connected up the display and an RTC. Works like a champ. You yes I did have to change one line in Adafruit_LEDBackpack.cpp from #ifdef __AVR_ATtiny85__ to #ifdef __AVR_ATtiny84__.

Since this validates the programmer shield and the backpack running on the tiny architecture, I'm stumped as to why it doesn't run on an ATtiny85. I also tried three different 85 chips which ran blink just fine. I wunder if one of the pins might need to be defined as output on the 85.

User avatar
adafruit_support_bill
 
Posts: 88093
Joined: Sat Feb 07, 2009 10:11 am

Re: 0.56" seven Segment Backpack Display Pul-up Resistors

Post by adafruit_support_bill »

Not sure why it would work on the 84, but not the 85.
In your code, are you using TinyWireM or the regular Wire library?
https://github.com/adafruit/TinyWireM

User avatar
mboroff
 
Posts: 96
Joined: Sat Feb 22, 2014 7:45 pm

Re: 0.56" seven Segment Backpack Display Pul-up Resistors

Post by mboroff »

TinyWireM. Comments in your example are clear to incommensurables include for TinyWireM.h and comment out Wire. H.

Also, had to change #ifdef for chip definition in backpack.cpp which affects under the cover include statement.

Locked
Please be positive and constructive with your questions and comments.

Return to “Arduino Shields from Adafruit”