Shared Projects by rfmerrill

sega genesis/mega drive 6-button interface PCB for fight stick

this is the tag “first-board-rev” in the github.

Emulates the original sega 6-button controller. Latest firmware expects MODE to be connected to pin 3 of the ATTiny404, but will work fine without it connected.

Parts used:

• 2x CD74HC257M96 (74HC257 in SOIC)
• 1x ATTINY404-SSNR
• 3x 0.1u X5R/X7R ceramic SMD caps (0805 on this revision)
• All resistors are 0805 68k-100k

This allows you to replace a 40 or 42-pin ROM or EPROM with a 27C322-like footprint, using PLCC NOR flash chips that are still in production.

This allows you to use a pair of PLCC NOR FLASH EEPROMs for a genesis cart up to 1 megabyte. The advantage of this over existing solutions is that it fits in a regular genesis cart shell WITH sockets!

The two EEPROMs are SST39SF040-70-4C-NHE-T, which can be programmed using the widely available cheap TL866-II programmer using the PLCC-32 adapter it comes with.

The PLCC-32 sockets I used are 69802-132LF from Amphenol FCI. Soldering them in place can be quite difficult with any method other than paste and reflow. To solder them on with an iron you might need to cut the plastic out of the bottom of the socket.

There are only a few more components:

• 2x 0805 0.1uF capacitors on the reverse side

• 1x 47uF electrolytic cap

using AUC logic and smaller components

C2: 0.047u for ~3.5 kHz, 1u for ~170 Hz

C1, C3-C9: 10u

R1: 6.8kohm

R2-R6: 220 ohm, lowest inductance possible (ERA-1AEB221C used – 0201)

U1: 74AHC1G14GW,125

U2-U7: SN74AUC1G17DCKR

In my build I added a 220uF electrolytic at the power input and added additional 0805 bypass caps directly across the power and ground of each gate (actually power and NC pin, as that is grounded).

Bigger track version.

J1 fits a particular board edge SMA connector I bought from amazon. Make sure you can find one that fits.

U1 is a 74AC14.

R2-R5 are all 220 ohm.

C1 is decoupling for the 74AC14.

R1 and C2 set the pulse frequency.