I'm working on a project to retrofit wireless connectivity into NES controllers. When I started the project and was doing research, I learned that both NES and SNES use the "same" protocol for transferring data (differing only in how many bits and what order they come in). So I started on the SNES, because then I have the option of only modding one set of controllers, building two receivers, and then it works with both consoles.
I've done the SNES part and everything works great. But the only/best data I could find online about the real wire protocol for the NES ( http://www.mit.edu/~tarvizo/nes-controller.html ) says "Every 60 Hz, the NES sends a 12us high signal to the Latch pin, telling the controller to latch the state of of all buttons internally. Six microseconds later, the NES sends 8 high pulses on the Pulse pin, 12us per full cycle, 50% duty cycle." This is definitely exactly what I observed with the SNES (except 16 clock pulses). But when I built the NES receiver, it wasn't working reliably.
As far as I can tell, the NES does not quite do this. On the NES, I'm seeing only a ~4 microsecond (not 12) latch pulse.
The first falling edge of the clock is only ~9 us from the rising edge of latch (not 18), and the clock A) has a ~10 us period with B) only ~0.5us low (not 6).
Is this normal/expected? It's causing trouble for me.
I've done the SNES part and everything works great. But the only/best data I could find online about the real wire protocol for the NES ( http://www.mit.edu/~tarvizo/nes-controller.html ) says "Every 60 Hz, the NES sends a 12us high signal to the Latch pin, telling the controller to latch the state of of all buttons internally. Six microseconds later, the NES sends 8 high pulses on the Pulse pin, 12us per full cycle, 50% duty cycle." This is definitely exactly what I observed with the SNES (except 16 clock pulses). But when I built the NES receiver, it wasn't working reliably.
As far as I can tell, the NES does not quite do this. On the NES, I'm seeing only a ~4 microsecond (not 12) latch pulse.
Attachment:
The first falling edge of the clock is only ~9 us from the rising edge of latch (not 18), and the clock A) has a ~10 us period with B) only ~0.5us low (not 6).
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Is this normal/expected? It's causing trouble for me.