[Solved]What is the difference between zapper trigger and Up

Discuss emulation of the Nintendo Entertainment System and Famicom.

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geod
Posts: 128
Joined: Thu Nov 26, 2015 12:02 am

[Solved]What is the difference between zapper trigger and Up

Post by geod » Mon Feb 18, 2019 8:44 am

From my understanding both set the bit 4 of the console port so it should be the same.
I'm testing with zapper_stream rom of rainwarrior from https://forums.nesdev.com/viewtopic.php?f=9&t=13021 with Mesen, Bizhawk, FCEUX.
If i select a zapper for the port 2, the rom works as expected and detect the trigger pulling but if i select a second gamepad and press Up button nothing happens. So it must have something wrong in my understanding.
Can someone help me pointing out the issue pls?
Thanks!
Last edited by geod on Tue Apr 16, 2019 1:56 am, edited 1 time in total.
3dSen - Play NES games in 3D & VR
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lidnariq
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Location: Seattle

Re: What is the difference between zapper trigger and Up?

Post by lidnariq » Mon Feb 18, 2019 11:39 am

The standard controller does not give you all the bits simultaneously. When you read $4016 or $4017, you only get one button at a time, and that from the least significant bit.

The zapper, in contrast, only has 2 "buttons", and those are received simultaneously. (Unless you're on the Vs. System)

geod
Posts: 128
Joined: Thu Nov 26, 2015 12:02 am

Re: What is the difference between zapper trigger and Up?

Post by geod » Mon Feb 18, 2019 6:08 pm

I get it now, thank you :)
3dSen - Play NES games in 3D & VR
http://www.geodstudio.net/

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