July 2014 Lab Journal

2014-07-19 I finally got around to soldering the rev b FM PBC boards. I noticed while soldering that I forgot to order 1 component - the reset generator. Luckily Digikey shipping is usually at or near the speed of light and I should have it by Monday. The major difference between this and the first revision of the FM PBC is that this one has complete isolation between analog and digital circuits. All of the analog circuitry is tucked in the lower left corner, and if you look closely you'll notice it has ground place separations as well. Let's hope this will address the noise interference found on the first revision.  As soon as I get the reset generator and can program the CPLD (firmware should be nearly identical to rev a) I will post audio samples.

2014-07-27 I programmed the CPLD on the rev b FM PBC today, and, success! Glorious YM2413 music with no crosstalk from the digital circuitry emanated from my Sony Trinitron!  There is one major bug left to iron out; I can currently only get the FM module recognized on a Model 1 Genesis, both my Model 2 Genesis do not recognized the FM chip and refuse to play FM music.

Made a few changes to the VHDL code of the FM PBC today and BANG it works on the Model 2 now. Getting the Model 2 working seems to have interfered with the FM disable feature (where you hold UP during power up to disable the FM module) - this is just a minor setback; getting the Model 2 working is a MAJOR accomplishment. I'm beginning to wonder though exactly how useful the FM disable feature really is - I mean, if I'm buying this thing it's because I want to hear the FM sound right?

Check out the demo video to the right to see both Genesiseseses in action with the FM PBC.

Here's a quick audio sample from the Double Dragon intro screen I recorded by simply connecting the Model 1's headphone output to the MIC input of my PC. 

Double Dragon Intro FM Music

I'll assure you that the noise you here before and after the sound sample are a result of my horrible recording setup!