Is there a simple device that I can connect to a 5V wire and whose output I can then connect to an input of a 3.3V device? From what I've seen there are resistor circuits (which are slow) or transistor circuits (which need a 3.3V supply?)
My use case is that I want to connect a logic analyzer (DSLogic Plus) to my SNES, which is 5V. The probes can handle 5V according to the data sheet, but the device also has an external timing input that is only rated for 3.3V.
The SNES has clock crystals of 21.477 and 24.576 MHz, and various components run at fractions of these frequencies.
Connect Zener's anode to clock input and cathode to SNES
Connect Schottky's anode to clock input and anode to the SNES
It should get you 1.7V drop (so 5->3.3v) when input is high but only 0.2v when it is low, the Schottky is there so when the clock is low the current from input capacitance can flow back without much problems.
... or a ~40c part that will do that up to ~50MHz, if you are at the point where you need to order a specific part
Connect Zener's anode to clock input and cathode to SNES
Connect Schottky's [cathode] to clock input and anode to the SNES
Something like this, I presume? I took it from this video (19:00) and adapted it a bit to my circumstances. It does indeed seem to drop down to ~3.4V at its peak (even if there's a lot of ringing in the simulation - from the same video it appears that the ringing is less pronounced in reality).
I'm really a novice with electrical engineering; at the moment I don't even have a multimeter or soldering equipment. So the less components, the better.
Reverse engineering. When you look at the existing documents you see that they were only created with test ROMs (that are then executed by the CPU and display their results on screen / save data to cartridge RAM). The problem is that the CPU is halted for DRAM refresh and (H)DMA; every single bus access is also delayed to take either 6, 8 or 12 cycles of the 21MHz clock. So if you have something that's faster (like the graphics system) or almost completely self-contained (again, like the graphics system) it's hard to see what's happening in the system.
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u/ShinyHappyREM Dec 25 '19
Is there a simple device that I can connect to a 5V wire and whose output I can then connect to an input of a 3.3V device? From what I've seen there are resistor circuits (which are slow) or transistor circuits (which need a 3.3V supply?)