MiSTer FPGA Forum

Hi MiSTer friends!

So I just received my new v6.1 I/O board + Genesis DB9 adapter from aliexpress..

I started by hooking it up without connecting a Genesis controller, no smoke, everything was fine, and when I connected a wired controller to the DB9, the MiSTer instantly reset! Well that seemed like bad news..

After that the right button is always stuck while other buttons work just fine.

Measuring with multimeter on the SNAC I found something strange with one of the level shifters, the third one from I/O board USB connector always measure 3V + 0V while every other shifter measure about 1.6V on both pins (from the side with one pin to the side with two pins).

The same strange voltages was seen after desoldering the 4th shifter as a replacement for the 3rd (disabling Y + DOWN in the process).

I have now switched back to my old v5.5 I/O board and the third level shifter measure the same 1.6V on both pins now.
So I fear my v6.1 board has had some kind of hardware related failure. Any idea on parts that could be broken on it ?

I'm not sure if I could get a new I/O board from aliexpress as it seems difficult to pinpoint the root cause.
I also worry it had an impact on the DE10, but I assume there is some kind of protection on the pins going into the DE10 from the I/O board?

After some help from pgimeno on IRC and probing around on the boards.. it has magically healed itself !

If I had to guess what fixed it, either probe pressure on the components or re-seating the I/O board.

I made a quick diagram of how P7 pins are connected to the SNAC. To make it easier for anyone wanting to debug this on their own board. The right most column has which level shifter is connected to what P7 pin.

Seen from bottom of I/O board looking into the USB 3.0 port:

StdA_SSTX+: RN12:3 : 1 on lower pins USB 3.0 port : P7:10 (100 Ohm) : LV7   : 7th
StdA_SSTX-: RN14:4 : 2 on lower pins USB 3.0 port : P7:5  (100 Ohm) : TX-   : 1st
GND DRAIN : RN14:3 : 3 on lower pins USB 3.0 port : P7:6  (100 Ohm) : GND_D : 3rd
StdA_SSRX+: RN14:2 : 4 on lower pins USB 3.0 port : P7:7  (100 Ohm) : RX+   : 5th
StdA_SSRX-: RN14:1 : 5 on lower pins USB 3.0 port : P7:8  (100 Ohm) : RX-   : 6th

VCC       :        : 1 on upper pins USB 3.0 port
D-        : RN12:1 : 2 on upper pins USB 3.0 port : P7:2  (100 Ohm) : D-    : 2nd
D+        : RN12:2 : 3 on upper pins USB 3.0 port : P7:1  (100 Ohm) : D+    : 4th
GND       :        : 4 on upper pins USB 3.0 port