SNES controller ports: maximum current draw?

[lingomaniac88]

I'm working on a project in which I emulate an SNES controller using multiple wireless devices. Specifically, my setup is a network of Xbee Pro modules, one of which is attached to the SNES controller port (with a microcontroller in between). The main concern right now is how to power everything while minimizing the chances of human error.

While I can hook up my "controller" to an external power source, I still feel that the easiest solution is to just have the SNES controller port power everything. (From basic experimentation, using an external power source and connecting its ground with the SNES ground will leave the SNES on if I switch the console off before cutting power to the controller.) While various SNES schematics that I've found via Google suggest that the 5V signal on the controller ports is just what comes out of the 5V regulator, there's still the issue of making sure that the SNES can handle the Xbee Pro's current draw. According to the Xbee Pro datasheet, the module has a peak Tx current of 250 mA (I'm using a wire antenna, not an RPSMA one). From what I've seen, the limiting factor is the SNES power supply, which is rated for 850 mA, as a 7805 voltage regulator can typically handle more than this.

I know that I could probably find a beefier power supply or add in a 1000 uF capacitor to help mitigate bursts of current when transmitting. Also, there's probably a bit of a safety factor built into the power supply, so it wouldn't be the end of the world if I pushed the envelope for a brief period of time every now and then. Still, it would be nice to get a second opinion.

tl;dr: How much current can I safely draw from the SNES controller ports? Can I connect something that with peak current draw 250 mA as is? Should I take some additional precautions?

[lidnariq]

A larger capacitor will increase the likelihood of exceeding the permissible current draw in the first place while it's charging.

ISTR that the permissible peak power draw from each controller port is approximately 50mA. ( but see also viewtopic.php?t=10693 )


You might want/need to use a standard 433MHz radio pair instead of an xbee. Or maybe TI's ChipCon parts, like the CC1010 or CC2531

[Memblers]

That would be 250mA @ 3.3V. The current at 5V would be less, but still significant.

I've wondered if I'll run in to the same issue when I add a wireless module to an NES peripheral I'm working on. I believe one can safely charge a big capacitor if you include some kind of inrush limiting device, such as an NTC thermistor.

[qwertymodo]

The voltage pin on the controller port is just connected directly to the main 5V rail, so the available current is only limited by the power supply/voltage regulator (minus the power draw of the rest of the system).