FV-1 Multi effect full forum project ready to go. (ShimmerVerb Also)

[Ice-9]

FV-1 Full project for DIY multiFX pedal by Mick Taylor 2013

First a brief description of what this is about.
I'm sure many of you have heard about or experimented with the Spinsemi FV-1 reverb/multi effects DSP chip just like
I have myself. I have been meaning for a while to bring a complete DIY'able project that anyone can easily build to
the diy pedal forums that I visit. So basically here it is.
I have managed to get this finished with the help of quite a few other members here as well as from other forums
whom I will give mention and thanks to as I go along. The pedal is a simple mono design that has true bypass and has
two different build options. As well as being able to etch a single sided PCB easily at home I have a fabbed double
sided PCB which I can make available.

I believe this makes a great development platform for a simple DSP FV-1 pedal as it has built in ability to
reprogram the software without removing the Eeprom from the circuit.

OK on to a couple of basic sound samples trying to demonstrate a little bit of what to expect, recorded using just a
phone to capture sound and video.

The first vid is of FV-1 pedal loaded with the tape echo firmware called eTap2HW written by Piet which emulates the
sounds of the 'MeazziEchomatic' multi head tape loop echos. The patches have been written to emulate the sounds of
Hank Marvin of the Shadows and his unique sound, but are not restricted to this as many other artist used these tape
echo machines.  

The video starts with a clean bypassed sound followed by a couple of bits to try and demo how the echo sounds.The
rest of the vid is pretty much just a single muted strum to capture how the echo's fall with different settings, the
bits where the feedback is turned up is so the tape decay of repeats can be heard.


The second Vid is the same pedal loaded up with a delay and a Shimmer reverb.
Again the vid starts in bypass then has a little bit of the delay effect, the rest is of the Shimmer Reverb as I try
to show what all the knobs do to alter the effect from very little shimmer all the way to a synth like effect.

   

Schematics of both versions of the circuit, one has the output opamp in a non-inverting gain stage for any gain
recovery that might be needed in certain firmwares, but by leaving out a few components and inserting a jumper link
it can be converted into a straight non inverting buffer as in the second schematic. (right click and save
schematics and to view better res.)





Description of schematic
The circuit based around TR1, R1,R2 and D1 form the PSU polarity protection circuit which was described in some of
R.G.s advanced power supply reverse polarity article, different diode type protections can be subbed if preferred.
this is then followed by a standard voltage divider network and filtering for 9V, ground and Vref, and 3.3v voltage
regulator for powering the FV-1 circuit.

Audio to the DSP is input is taken care of by IC1.1 (TL072) working as a straight forward non inverting buffer.
Audio out from the DSP goes through a non inverting gain stage around IC1.2. to convert to a standard non inverting
buffer on the output simply leave out C9,C10,R11,R12 and put a link in place of C10 or R12, which will make the
circuit as in the second schematic.

The digital side of the circuit has at the heart an FV-1 DSP (IC3) with a 24LC32A Eeprom (IC2) which holds the code
for upto 8 programs. These programs are controlled by the PIC12F683 which outputs the 3 bit binary code that the
FV-1 needs to select any of the 8 different programs. The programs are selected using a potentiometer (VR4) on the
input of the PIC chip. It is also possible to use a toggle switch to select a program if sat you wanted 2 or 3
programs only (say you wanted 3 reverbs Room,Hall and plate etc)There are wire points on the pcb that would allow
for this.

PIC12F683 The code for the pic has been written by another forum member called Ian or better known as slacker and
is a great bit of glitch free code. So thanks Ian for allowing me to use this code.

Slacker has also done much FV-1 coding and has been a great source of information regarding the FV-1 both here and
at the Spinsemi website forum, as well as having his FV-1 project on the go.

24LC32A chip is the chip which holds all the external programs that can be loaded into the main DSP and I have
provided a way to re-program the chip with new effects code without having to remove the chip or dismantle the
pedal, and it takes about 10 seconds to read/erase and reprogram the chip with new code.

Next post I will show some build and layout pictures, see you all soon.

[Govmnt_Lacky]

Looking good so far. Can't wait to see what happens with this in the future!

[armdnrdy]

Thanks Mick,

Great sounds!

Look forward to the whole project!

Definitely a make a go at this one!

[deadastronaut]

Nice one mick and ian..

can't wait to get that shimmer,delay sound...superb.

will you list everything that is needed to build,programme for
for us digital noobs too. 

[Ice-9]

Nice one mick and ian..

can't wait to get that shimmer,delay sound...superb.

will you list everything that is needed to build,programme for
for us digital noobs too. 

Yes everything will be posted and explained with a little tutorial on how to get the programs flashed to the chips as well. Once I have finished posting all the details here I will try and put everything together in a pdf file for the full plans and construction details in an assembly type of layout.

[deadastronaut]

Brilliant, what programmer/hardware would you suggest buying?

[Ice-9]

FV1 Multi effect Part 2

This second part of the project will look at the two PCB's but will mainly focus on pictures of the double sided PCB.

The EEprom can be soldered onto the PCB without programming it first, the PCB has been designed so it's possible to program the chip once assembled as the whole aim is to be able to write your own software and then send it to the pedal. On the other hand the PIC12F683 chip needs programmed before soldering onto the PCB, I could have put programming points on the board for this but as it is only needed to be programmed once means it isn't needed. Having said that it is possible to re-program it on board if it needs to be (although it would be fiddly to do).

I have designed the board for pcb mounted components. ie jacks, pots and switches. I know some prefer not to mount this way and the the pots could at least be wired separately, but for now I will only be talking about building it using these two PCB's . Further down the line I may release a PCB for offboard controls and switches.

On to some build pictures

Single sided home etched pcb
This is the design and etch of a home made board that was part of the prototyping of the effect and is fully functional, and can be easily made at home cheaply and requires the pots to wired up offboard.


Next up is the PCB's I had fabbed, the circuit is exactly the same but being double sided is far better layed out and has all the components on the top side of the board whereas with the single sided board the SMD chips must be soldered on the underside. These fabbed boards are also what I am using in my commercial pedal design.



Next picture I have hand soldered the SMD components to the PCB the pic has been programmed before soldering. I would usually solder semiconductors last but it is far easier to solder these first in the case of SMD as the board can lay flat and there is plenty room to work around the PCB. If anyone want to work from these PCB's I could make them available with all the SMD components already programmed and soldered for anyone who doesn't like the idea of hand soldering these up.



PCB with all the components soldered in place apart from the potentiometers. Notice the missing components just above the output jack and just below the opamp, this is the schematic version that uses a non inverting buffer output stage giving the entire analogue circuitry a gain of one. (no gain). Also notice there is a wire link in place where C10 would be.



Final Picture for Part 2 is the complete and fully working unit, it has connections for 9v centre negative PSU as well as 9v battery.



Part 3 coming next, which will deal with software and writing effects to the Eeprom using a PC

[jk-fm]

Could the pcb be modded to use a rotary switch for the programs?

http://www.diystompboxes.com/smfforum/index.php?topic=89565.0

[Ice-9]

Could the pcb be modded to use a rotary switch for the programs?

http://www.diystompboxes.com/smfforum/index.php?topic=89565.0

There is no need to mod the pcb. Leave off the PIC12F683 chip and use the wire pads there to directly connect the switching circuit that you linked to, or even a 3 bit binary counter rotary switch. Only problem would be the physical size of the switch and if you have room to fit it in the enclosure

[deadastronaut]

''Further down the line I may release a PCB for offboard controls and switches.''

cool, i would prefer that.

[MetalGuy]

Nice project!

[Govmnt_Lacky]

@Mick

What is the 2nd 8-pin SMD chip next to the FV-1. Is that a 2nd onboard memory chip?

[Marcvv]

very nice project!!

[waltk]

Nice work! 

Where's the best (cheapest) place to get the FV-1 IC?

The schematics look like DipTrace output.  Are you planning to share the DipTrace files when the project is ready? (That would be great)

[defaced]

Nice project! Definitely interested in it, so I'll be looking from the side lines on this one. 

[Ice-9]

Nice work! 

Where's the best (cheapest) place to get the FV-1 IC?

The schematics look like DipTrace output.  Are you planning to share the DipTrace files when the project is ready? (That would be great)

If your UK based the best place to get the FV-1 is probs from Profusion, correct the files are diptrace and yes.

[slacker]

Looks great Mick, nice to see a lot of interest, be great if we can get more people into this stuff.

[slacker]

Brilliant, what programmer/hardware would you suggest buying?

I think Mick uses the PICkit2 programmer, this will program the EEPROM to hold the programs and the PIC used to select them.
If you have a computer with a serial port both the chips can be programmed using that, a couple of simple circuits and some free software. The EEPROM can also be programmed using a USB to serial converter cable. I'll post details when I get time.

[garcho]

Count me as interested, and impressed, bravo.

[Ice-9]

Brilliant, what programmer/hardware would you suggest buying?

I think Mick uses the PICkit2 programmer, this will program the EEPROM to hold the programs and the PIC used to select them.
If you have a computer with a serial port both the chips can be programmed using that, a couple of simple circuits and some free software. The EEPROM can also be programmed using a USB to serial converter cable. I'll post details when I get time.

^ Exactly what Ian says above. If you have a computer with a serial port then you can make you own programmer very cheaply with a few components and use free software. If you have only USB ports then the Pickit2 for about £18 is the best option, it can program lots of different pic chips and eeproms so can a very handy tool if you want to get into other PIC controller projects as well.