I've started working on this christmas gift which consists of a 8 LED "display" controlled by a Attiny84a microcontroller. I want it to ultimately display a message byte by byte.
However, I can't upload any code on the Attiny.
I am using Arduino as ISP for the programming interface (I've tried both a nano clone as well as as an adafruit metro mini - atmega328p).
For the IDE, I've been trying on versions 2.0.3 and 1.8.15.
The code I utilised for testing is the official blink example.
This is the Attiny core created by Spence Konde: https://github.com/SpenceKonde/ATTinyCore.
After uploading using programmer I do not get any errors.
The Attiny84a seems to have all the gpio pins high when powered on.
I've tested the mentioned core on a Attiny 85 as well and it worked perfectly with the blink sketch.
I apologise for posting this inquiry so close to christmas, but I am running out of time and am a bit desperate.
Any suggestion is welcomed.
Thanks in advance!
For informed help, please post a complete, hand drawn schematic of your wiring, being sure to show pullups, decoupling capacitors, etc., a photo of the setup, the code, using code tags, and error messages.
I found s workaround, let's say.
I managed to programme the attiny by selecting the 1MHz internal clock option.
Pin 4, however, which is the reset pin as well as pin 11 according to the documentation of the core, didn't work for me.
You can make it run at 8 MHz by selecting 8 MHZ internal clock and doing burn bootloader.
The reset pin cannot be used as a general purpose I/O pin unless a specific fuse has been set. Otherwise it's not an input or output pin! It's a reset pin. All it can do is reset the chip if brought low, and the internal pullup ls forced on.
If RSTDISBL fuse is set to disable the reset functionality, you can no longer reprogram the part normally, becasue reprogramming it via ISP requires a reset pin, but you disabled that and make it a crappy I/O pin (see note below), it's no longer a reset pin. If this is done. exotic HV programming equipment is required in order to reprogram it further (unless using a bootloader that can be entered on power on reset - and in any event, you cannot change the fuses in any way shape or form without an HV programmer once you've disabled reset.
And what do you get for that? An output pin that is extremely sensitive to ESD and picks up electrical noise very well (because it doesn't have the normal clamping diode - one guy with a longish wire on his reset pin set as I/O was going crazy, because it worked in some places, but if he moved it around his house, near the TV or microwave, it kept malfnctioning) or a MISERABLE output pin. As an output pin, the pin that's nominally reset is like a limp noodle. Vcc = 5V,. I = 0.5mA and the voltage drop across the patheticly weak drivers is already up to 1V.
That's why people don't generally disable reset
They recognized that on the modern full-sized AVRs (they don't need reset enabled for reprogramming, there's a different pin for that), and just gave up and stopped putting pin drivers on reset at all, so on many of the newest non-tinyAVR parts, all it can do is act as an input, or as reset, never output - just because it was such a pathetic output nobody wanted to use it)
