I now have the latest ssc-32 to tinker with. I notice that when I put a jumper on the “A” pins, VA, VB, VC, and VD all show a high reading (246 to 255). I would think that only VA should show a high number and the other three should be 0. The same thing happens when the jumper is put on the “C” pins. Is there something I’m missing here? I’m using the lynxterm analog input query buttons.
What happens when you have no jumper on any of them?
A lot of micro controllers have pull up resistor for inputs, so their unconnected voltage is high, I’m not sure about this for analog inputs though.
Also, if AI pins are not connected at all, they can fluctuate a fair bit from interference etc. as they don’t consume much power. If you need a low signal, you would want to connect them to ground.
With no jumpers 0 voltage is indicated. With a jumper to 5v on pin A or C, all pins indicate ~ the same 5v voltage. Perhaps there is a flaw in the new chip. This situation makes the ssc-32 effectivly have only one analog input. The same seems to also be true for using the pins as digital input. I also seem to notice some other unexpected behavior, but it needs further checking.
No flaws here. You must make all CMOS inputs either high or low, if you leave them unconnected there is no way to know what they will read. They will exhibit as you stated unexpected results. This is a very well known and common situation. Try connecting all 4 inputs to either 5vdc or gnd and read them. They will be correct.
I rechecked the manual and it does say that the pull up/down resistors are only in play when in the digital mode. Did some more testing, and with an analog voltage input, the resistors aren’t really needed.
The only scenario where pull-up resistors would be needed is when you’re adding an open collector output, or interfacing a switch as an input. If you are connecting the inputs to a CMOS or TTL device or an analog voltage no pull-up / pull-down resistors are required.
Hi Guys
I also have a question about analog input. I have it all working and can read, so thats not a problem. What i’m after is what sort of internal resistance the ssc32 has on an analog input (if that makes sense).
What I intend to do is build a tachometer (ir sensor connected to a binary up counter), then build a DAC using a voltage divider, so each pin off the counter has a different voltage.
e.g.
o o o o---o------------
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R1]1k]2k]4k]8k]ssc32 input (ascii art ftw :P)
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o---o---o---o---o----------
|
R2]1k
_|_
_its basically the above, cept with some transistors and an up counter, and i have a whole stack of 100k resistors 
.
The reason I ask for the resistance is that it will affect my choice in resistors (as 1/R1+1/ssc32 = 1/total_res), and like i said, i got a whole stack of 100k’s.[/code]
The ATMEL chip datasheet should have the specs on the resistance/current drain of the analog input pins.
Psst! If you use the code function, you can do ascii art with a fixed-width font. 
Lol thanks 
and thanks for the reply also zoomkat
If you wanted to measure yourself for the resistance/current draw of the chip pin, get a ~50k pot/resistor and a multimeter, and set up a voltage divider inputting the pin. Use one of the online java voltage divider calculators to calculate the pin resistance.
Right, now thats outta the way, i am all of a sudden having problems with input
I jumper pin A to +5v and i get 255, open i get 0
however
+5v_____o
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]
]<----
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Gnd_____o In ARegardless of the position of the pot, i seem to get 0 (I think its around 1kOhm, the pot)
Oh and i’m usin the lynx ssc32 terminal software as well.
Its probably something i’m missing, coz i have had it working before
Using a multimeter, measure the voltage from the wiper (input to the A pin) and ground and see if it changes as you move the pot, and also see if the ssc-32 analog input also matches the multimeter reading.
Lol, oh dear, its working now, same setup. Maybe it was coz it was a thursday
I never could get the hang of Thursday…