If you ever owned a Nintendo entertainment system (NES) you will be familiar with the blinking screen of death, most of the time a quick blow down the end of cart would fix it. Fast forward to this year when I seen this video on HackaDay where I drew my inspiration for this project.
I thought I could make a simpler version of the harmonica famicom board using at attiny85 a mic and a speaker. That’s when the Nes_blow_cart was born. It’s really simple all you do is blow down the end of the cart like you used to do back in the day and it plays a tune from a video game.
I always start phototyping my project on a arduion and breadboard because this is the easist way to do error testing. There is always that fear when moving from the ardiuno to using a attiny85 that somethings wont work or wont quite fit on the chip, luckly this time nothing needed to be modified and the external library’s were fine.
This is my second project that uses a attiny85 like i did on my one button remote. I also designed a PCB using Kicad, I had to measure the internal dimensions of the NES cart because i was using one of the posts inside the cart to proposition the main PCB
The hardest part of this project wasn’t the hardware, I needed away to play “music” this is when i stumbled upon the rtttl library’s. The rtttl format was using in the early 90’s on the Nokia phones where you could enter in your own custom ringtone from the keypad. I scoured the internet for some video game inspired ringtones I found some great Mario and Zelda ones Here is a good website to look for video games ringtones.
Back to the hardware, after waiting for the PCB to be spun it arrived and I hesitantly check to see if it would fit on the internal nes cart posts.
Long and behold it fitted now I can go about populating it with some of the bigger components. As you can see by the outline of the speaker and battery they over hang the board this is to save PCB and save money ;)
The overhung of the speaker and battery worked out quite well as you can see. Next up I needed to solder the switch off the board with a pair of wires and mount it down the bottom of the nes cart.
I didn’t have a drill bit small enough to drill holes in the case I heated a nail up with a blow torch and pushed it though to make the holes. It was a heart stopping moment but it turned out ok
Now that the switch is secured I need to sort out the sound sensor board mine was the FC-04 which is quite a common one found on ebay for cheap. I needed to remove the male header pins and extend out the mic off the board. Here is it with the components removed
Now to add the wires from where the male header pins were and also from the mic
Lets see give it a quick go see if it works
Now that I have it all in its place and working I needed to add the programming headers so that I can reprogram the attiny85 without taking off the board. I wish I had done this on my One button tv remote would have made it easier to reprogram. First I had to cut a gap in the casing.
Then it was just a matter of soldering the six wires from the custom PCB to the headers and hot gluing it all in place. Giving it a test to see if I had wired it up correctly and put a piece of tubing to keep the wires in check.
Here is a quick tip for anyone laying out there PCB is that if you have a speaker on your board don’t put it one of your pins your going to be using to program it with or you will get this
Now all that’s left is to give you a look at the finished article and let you at the code and Kicad files
Github files for the attiny85 code and Kicad PCB files