attiny+oled not working on breadboard

Other Hardware Displays
1

Hi all,

apologies if this is not the relevant section, it seems the most appropriate to me.

I have written a sketch for an ATtiny85 which displays some test in a 128x64 I2C oled.

When using the Tiny AVR Programmer, everything works fine, text is displayed correctly.

Now I want to make the whole setup permanent, so I thought about moving it to a PCB, but, before doing that, I wanted to test the setup on a breadboard, powering the tiny and the oled with a 3v cr2032 coin cell battery.

The setup is shown in the picture in attachment

Using this setup, the display doesn't show anything.

I know the tiny works fine, because I have attached an LED which is turned on at startup and it is powered properly.

Can anyone point me in the right direction on what I am doing wrong?

Thanks in advance!

attiny_oled_bb.jpg
attiny_oled_bb.jpg1791×732 220 KB

2

Have you measured the voltage at the supply for the display?

3

Yes, I have
It's 2.80 on both sides (on the left of the battery, in my fritzing diagram, and on the right) without the LED, 2.75 with the LED ( which is positioned on the right of the supply for the display.
Do you think there's something wrong with my battery?

4

Do you think there's something wrong with my battery?

Not necessarily. Measuring the voltage is the first step that I would take in troubleshooting the problem.

5

True, I should have mentioned I had already measured voltage.

Anyway, I have put two 3V CR2032 batteries in series and managed to successfully light up the screen, but still it sucks: I have seen people doing much more complex things with the tiny and an oled using only one battery (like this business card, or this videogame), I can't believe mine is not working...

One thing that came to my mind is the Oled is drawing too much current: I got it from ebay, don't have a datasheet for it, but it would be very surprising: it's monochrome, should draw very little current...

6

2 things that i would try.

  1. Put a 10K resistor from physical pin 1 (reset) to ground.
  2. Put a 0.1uf (bypass) cap from phtsical pin 8 (Vcc) to physical pin 4 (ground).

Both of those things are more or less required in any tiny85 stand alone circuit.

Are pullups (SDA to Vcc and SCL to Vcc) installed on the display board? If not they must be provided.

7

Unfortunately, neither the 10k resistor nor the 0.1uF capacitor worked for me...

I am not sure about the pull up resistors, what I have is the the screen in attachment

The small little cubes should be resistors, if I am not wrong, but I can't really tell how big they are and if they are pull ups

20190128_230436.jpg
20190128_230436.jpg2160×2160 634 KB

8

I might have an answer to my problem, posting it just for reference if anyone else has the same issue

I just found out there are two versions of the ATtiny85, as described in this post (What can the ATTiny85 do? - #10 by JChristensen - Microcontrollers - Arduino Forum): one is the ATtiny85-20PU, which requires 2.7-5.5V to run; the other is the ATtiny85-10PU, which requires 1.8-5.5V

My ATtiny85 is the 20PU version, so it might be the OLED is not working because the tiny is drawing too much current

WARNING
I haven't tested my setup with an ATTiny85-10PU, this is just an hypotesis!!!