Controlling FV-1 S0-S2 with micro

finkster · Post by **finkster** » Wed Jun 03, 2009 3:39 pm

Rather than tying S0-S1 and T0 high with the 20k resistor and shorting them to ground to change effects, I am Tying them to ground with 20k resistors and using outputs from a 16F628A to to input high values to S0-S2 for the different effects. My question is What is the maximum/minimum input voltages for S0-S2 and T0? Also can the #5 internal "test" program be used just as a bypass meaning no effect added to the input signal? The reason I am doing this is so that I can use the Picmicro to display the effect and pot description for each effect as it is currently being used. Any info would be great. I have been playing with the FV-1 chip for a while and love it.

frank · Post by **frank** » Wed Jun 03, 2009 5:23 pm

The FV-1 is CMOS based so typically a high is anything over VCC/2 and a low is anything below VCC/2. But you want some noise margin in there so the closer to 3.3V for a high an 0 for a low, the better.

You could use #5 as a bypass but you may hear something in the bottom end of a signal as it is not a true bypass.

finkster · Post by **finkster** » Wed Jun 03, 2009 9:29 pm

Thanks Frank. This info is much appreciated.

differo · Post by **differo** » Mon Dec 20, 2010 6:28 am

bringing this thread to life:) I was thinking myself to try this, switch s0-s2 with pic microcontroller. haven't been able to find sufficient information on how to this, if there is anyone out there that has been succesful with this please throw some help. what I want to do is probably the obvious: two momentary switches that control the pic mc like up/down which are converted to binary output on some of the pic ports that switch fv-1. This part could be tricky as I have 16f877 mc at hand and even if I read in datasheet that it can work 2-5V people report that it doesn't work under 4V. Anyway if it can work on 3.3V than I could simply use the output pins on some port and write 1(high) which is 3.3V then, this would work as a switch? also on the other side I want to control a lcd displaying which current effect is current and maybe even labels for the pots (effect, mix, time etc..)

If there is anyone that has already done something like this please give me some guidelines (or more if you can

). I have icd2 and this microcontroller (16f877) I have display, crystal etc.

frank · Post by **frank** » Mon Dec 20, 2010 10:50 am

I do not have any experience with the 16F877 but here are a few general tips for any micro to control the FV-1:

If you can get the micro to work well at 3.3V then it should be fine to connect the port pins to S0-S2 on the FV-1.

If you need to run the micro at a higher voltage then use open collector ports on the micro to control S0-S2 and pull each pin high to 3.3V through a 1K resistor.

If you want to use a micro in place of the EEPROM it must respond with the proper data to every clock on SCK, the FV-1 does not support clock stretching. So you will generally want to tie SCK from the FV-1 to an interrupt pin on the micro.

differo · Post by **differo** » Mon Dec 20, 2010 12:01 pm

Thanks for the fast response frank! First of all - I do not plan to replace eeprom with micro, micro should only switch fv1 and show something on the lcd (which is the easiest part).

I don't know what do you mean with open collector pins, I believe that if I run pic on 5V(as I usually do) than it will output 5V if I set the pin to 1 (i.e. high). If you could explain how I can connect that pin to the 3.3V (I'm guessing the 3.3V from the power supply for FV1?) and than to the one of the s0-s2 pins. Schematics is the one here:
http://www.tonepad.com/getFile.asp?id=122

But actually I made some changes (from the previous build in order to make it work - added 15pF cap and different power supply and even a blender circuit for those two reverb programs that are wet-only), thou basically it's that schematics. When I have some time I'll re-do that layout with every changes that I made.

frank · Post by **frank** » Mon Dec 20, 2010 5:35 pm

differo wrote: I don't know what do you mean with open collector pins, I believe that if I run pic on 5V(as I usually do) than it will output 5V if I set the pin to 1 (i.e. high).

Some micros have some pins that are "open collector", these pins can only pull down to ground, they cannot pull up to the positive rail, see http://en.wikipedia.org/wiki/Open_collector

You add a resistor to the desired positive voltage, this allows a 5V micro to drive a 3.3V device because the open collector pin on the micro can only pull to ground, the 3.3V is supplied through the resistor.

I do not know if any of the pins on the 16F877 are open collector but if there are then use them to control the S0-S2 pins on the FV-1.

papiro · Post by **papiro** » Sun Jan 16, 2011 12:09 pm

Hello, it is possible to handle both inputs S0-S2 as POT0-POT2 with the PIC. In the first case is to make an attenuator resistors, the second is to make a PWM output on the PIC and add an external low pass filter to the output of the PIC. If you want I can send an explanatory scheme.

frank · Post by **frank** » Sun Jan 16, 2011 2:31 pm

papiro wrote:Hello, it is possible to handle both inputs S0-S2 as POT0-POT2 with the PIC. In the first case is to make an attenuator resistors, the second is to make a PWM output on the PIC and add an external low pass filter to the output of the PIC. If you want I can send an explanatory scheme.

Post or email the schematic and I'll be happy to look at it and comment on how you may do this.