techtravels.org

inital results on error correction

While I have yet to actually implement the full-scale error correction as I want to, I did some manual tests today. I basically took a track that I was erroring out on, and swapped in 1-bit away values for the bad bytes.  In some cases, it appeared...

Latest articles

pullups

These are all 2us per division on the scope.  Top trace is the actual MFM, bottom trace is the entering and exiting of my ISR.  You should see an entry into the ISR for every falling edge, and every ~2us afterwards. 1k...

proof of concept works

Today is the first day in months that I’ve made what I consider good progress. I am now able to read any track(so far) off of any disk with 100% success including checking and relying on the checksums. I read...

my checksum algorithm

So I’m using an XOR checksum to detect errors in the transfer between the SX and the PC.  I always thought it was a reasonably strong checksum, even though it’s still an 8 bit checksum. I found a neat...

good data vs bad

So you’ve seen me talk about good data and bad data.  But what’s the difference? Good data looks like the picture I posted awhile back here. Note the very even spread of 4—4—8.  Every pattern is...

AFP 0.2 WIP SX code

I’ve put some work into cleaning up the SX code tonight. I’ve removed some code sections no longer needed, and added documentation where it was lacking. Code should be commented pretty good. I’ve also...