Posted By
MMS
on 2019-01-10
15:07:58
 |  Re: Use of Homebrew wifi modems with the plus/4 safe?
Actually the User Port never expected to be overloaded, the specified maximum ampere is 0.1A.
Definitely with an OLED equipped device is possible, but the machines get old, and may not tolerate peak currents any more.
From the manual:
"Q: How much power does the WiModem use?
A: The WiModem uses an average of ~80mA while transmitting and ~25mA
while receiving. OLED option uses ~10mA more current."
I suppose the CN1 or CN2 can be connected to an external power source, but I could not find any technical decsription of them.
Maybe I will try Lemon
Worth to mention, that some of the screen and speaker noises reported to him, the developer linked to some not properly shielded cables, and maybe too close monitors.
From the developer, as some guys reported simillar screen issues on the C64Reloaded MOBO:
"Just like many user port devices, the WiModem doesn't use constant power. During transmission and receptions it goes to sleep meaning that it uses virtually no power. When it wakes up to do a reception check (low current) or and does a transmission (high current), this results in a tiny ripple in the 5 volt supply rail. The Mk1's fake 8701 and the Mk2's built-in 8701 circuitry can't handle any ripple at all apparently. The original 8701 has no issues.
The solution that Jens told me to add to the WiModem is a simple LC circuit to help smooth out the power surges. I am not going to change the WiModem hardware. It works without screen artifacts on real C64's, including every revision motherboard, the C128, SX-64, Vic-20, and Plus 4. So, I don't see a need to change it. Since there are other user port devices (besides WiFi modems) that exhibit the exact same issue on the C64Reloaded boards I think the fix should be there. Smile
If you build the proper 12v ->5v regulator then you should not have any issues. It could be that the C64Reloaded's 12v power source can't handle spikes in the load that is actually what is causing the ripple to be severe enough to affect the fake 8701 - or it could just be that the fake 8701 is not tolerant to any amount of ripple. A few people who have done the mod to the WiModem (to isolate pin 2 from the user port and power the WiModem itself directly) are using a 5v USB power source, like a wall adapter or a rechargeable "
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