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sailor
Registered: Jan 2002
Posts: 90 |
C64 Modding: LEDs / Switches
Hello All,
Not sure if this has been discussed here before, but can anyone provide circuit diagrams or connection diagrams for hardware mods like LEDs and/or switches.
Some stuff i can think of is displaying ZP$01 / VIC bank / drive reset / c64 reset / pause processor / data activity led for drive or serial channel / change(or ground) color bits...
I used to have few of these circuit/connection diagrams but they are lost somewhere.
Some of the stuff above is really easy to do, but is there a collected documentation of the stuff anywhere, feels unnecessary to invent the wheel again ?
Regards
Jani
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Frantic
Registered: Mar 2003
Posts: 1647 |
If anyone has something, feel very free to add it to http://codebase64.org
I would be happy to have such content there. |
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Devia
Registered: Oct 2004
Posts: 401 |
blah.. would be more interesting to build a "sniffer" board with display and backlog and ML/PLA/Clock/VIC translator/visualizationcapabilities'n'stuff... oh wait.. any decent Logic Analyzer does that ;-)
oh, almost forgot.. WHY?! |
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ready.
Registered: Feb 2003
Posts: 441 |
When doing such kind of things I use the 2N7000, which is a very cheap MOSFET switch. It is good because it doesn't load the line (pin) you are monitoring, in other words it requires a very small current to turn on. Then it can drive a diode. Use a 390 OHM (or similar value) to limit the diode current around 12 mA. The only drawback is that too many of these MOSFETs will cause capacitance effects that might slow down the computer operation, but the C64 is slow enough not to suffer of this problem. I successfully put around 10-15 MOSFETs in my modded C64.
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ready.
Registered: Feb 2003
Posts: 441 |
Oh, by the way: NEVER connect the series of resitor + diode directly to the pin you are monitoring or you will most likely kill the chip you hocked on to. Most of the signals in the C64 are just "signals" and don't have enough power to drive a LED.
So again, use 2N7000 or similar stuff as a buffer. |
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sailor
Registered: Jan 2002
Posts: 90 |
Thanks for your replies.
@ready.: I recall having BC547-transistors, but with additional 1kohm resistor on the "signal". I don't know the differance against the MOSFET solution ?
Also, do you remember where you picked the signals from (like IC and/or pin-number) and what their function were ?
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ready.
Registered: Feb 2003
Posts: 441 |
Hi Sailor,
the solution with BC547 might also work, but you need the additional 1kohm resistor to limit the base current from the commodore IC pin. The advantage of using a MOSFET is that the current is already limited, so you don't need that 1kohm resistor.
about the pin I used...well it depends on what you want to monitor with your LED. I needed to monitor the status bits of location $DE00, so I hocked up a bus comparator to generate the chip select signal for a 573 latch IC. The data bus was linked to the input of the 573 and 8 MOSFETs to the output of the 573.
Let's say you want to monitor the SID chip select signal, so that the LED blinks every time the SID is accessed for read/write, just connect the gate of the 2N7000 to the SID chip select pin (SID pin 8) and follow the scheme above for connecting the LED.
Here is the final result: http://fotoalbum.alice.it/alice/danieleredivo/engine-simulator/ |
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Mace
Registered: May 2002
Posts: 1799 |
Cool! Hardware mods!
A track & sector display on a discdrive would be nice.
Like, what you have in an Emu.
Any schematics for that? |
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ready.
Registered: Feb 2003
Posts: 441 |
here you find the file engine sim.zip:
http://mio.discoremoto.alice.it/danieleredivo/
it contains the schematics (beta version, could be improved, but they work as they are), a brief instruction of what this modded c64 does and a sample program adapted for a standard c64 (use a paddle if you have one).
I use this modded C64 at work to simulate the engine speed signal according to the fuel amount injected into the cylinders. In the sample program you can control the fuel amount with a paddle and the c64 responds according to the parameters of the engine (inertia, friction and load) solving a differential equation at 50Hz. The sample program uses the SID as speed output, while the real modded c64 send the speed signal out from one of the connectors as an open/close opto switch.
at the start of the program just hit return when asked teeth number. do not let the speed go over 700 rpm or I think the program crashes.
have fun!
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sailor
Registered: Jan 2002
Posts: 90 |
Hello,
Found a letter from a scener who had gathered some mods, i don't know if or which board revision this goes for but perhaps its same for all ?
Note: You do this on your own risk, these are not necessarily tested/verified and you will void the warranty :)
Any feedback/corrections always welcome!
Drive reset:
"Serial port PIN 6(reset)" + "pushbutton" + "ground".
Drive led/data activity:
"Serial port PIN 5(data in/out)" + "LED-circuit"
Display IRQ(SEI/CLI):
"Cartridge port PIN 4(IRQ)" + "LED-circuit"
Display graphic bank (2 LEDs used in this one):
"U2-6526 PIN 2(PA0)" + "LED-circuit"
"U2-6526 PIN 3(PA1)" + "LED-circuit".
"LED-circuit" corresponds to the circuitry mentioned above in this thread.
"Pushbutton" is a normal pushbutton used in electronics.
And again, you do/test this on your own risk!!
/Jani
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goto80
Registered: Jan 2002
Posts: 138 |
this one is a bit full on, but there are some nice features (although it's not really LED-visualizers and such) -> http://www.bigmech.com/misc/c64mods
i especially like the SID feedback thingy. |
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