Discussion N64 Controller CNT-NUS required components

Joined
Feb 12, 2020
Messages
73
Likes
105
Location
Canada
I've been working on designing my own PCB for an N64 controller for a little bit now, similar idea to the famous RDC chip that Downing uses in his portables. I know there is an N64+ controller chip coming soon thanks to the great work of some of the folks on these forums, but I'm using this as an exercise for myself in bolstering my EAGLE skills, and I won't lie it's really fun as well.

20160524_195419_zpsbhsncmas.jpg

In my process I've been wondering what components really are necessary to get the CNT-NUS chip to work. From the official controller chip pinout thread I know that the OSC 1 and 2 must be connected to their respective 5.6k and 1M resistors and then to the CLK chip, but what about all of the other capacitors, resistors and fuses?

bb_edition.png

I see RDC included quite a few of these components in his board, but I keep wondering what components really are necessary... which has led me down a small rabbit hole of determining what the values of each one of these components are and if similar components can be sourced from sites like mouser or digikey.

So here is my progress so far.
Resistors are easy to test, simply check them with the OHM setting on any multimeter, but capacitors are trickier since to get an accurate reading they need to be removed from the PCB. What I've done is desoldered a few capacitors I deemed necessary based off of RDCs board. Using the DC V setting on my multimeter I can touch each lead of the cap and discharge it to 0V, then switching to CAP mode I can then measure the capacitance. Here's what I've found so far:

N64_Controller_200010_Top_CLEAN.jpg


C3 = 1300pF
C4 = 1300pF
C5 = 1050pF
C6 = 0.11uF
C7 = 1200pF
C9 = 1100pF
C10 = 1uF
C14 = 91pF

Additionally, D1 is a 3 pin SOT23 diode in the BAT54 configuration, where pin 1 is the anode and 3 is the cathode. From the controller schematic and using the continuity test on my multimeter, it's easily seen that pin 2 is bridged to pin 1.
YJ5SQ.png


So this leads me to the discussion... Has anyone else (I guess besides RDC, who doesn't seem active on the forums) gone down this rabbit hole and started trying to measure and record each of the components on the controller? Is there a point to all of this or am I wasting my time? I'd love to discuss this and dig deeper.
 
Joined
Feb 12, 2020
Messages
73
Likes
105
Location
Canada
So it seems like most capacitors are there for decoupling, and not necessary for the controller to work. Thing is, even though the chip can be used without these capacitors... should it be?
 

Gman

RTFDS
Staff member
.
.
.
.
.
Joined
Feb 25, 2016
Messages
1,412
Likes
2,777
The components on the diagram on bitbuilt are the only required ones I believe.
 
Joined
Feb 12, 2020
Messages
73
Likes
105
Location
Canada
The components on the diagram on bitbuilt are the only required ones I believe.
Yeah I'm slowly figuring out that all the other components don't seem required. I'm still new to PCB design but it seems like they're all there for stability and decoupling. I'm interested to know why RDC decided to keep most of the components on his N64 controller board. I spent some time designing a board based on his for use in my own portable, but I'm on the edge and considering removing all of the decoupling caps besides the one needed for the FRAM chip I'm going to integrate. This is what I have so far it's a very rough draft, but if they're all non essential I might have just spent hours working on mapping the controller out for nothing :P It was still fun!
Capture.PNG
 
Top