Duggle

d2k, this could be done using digipots and cmos analog switches, or with LDR/LED and relays. Either way there would be a rather significant design effort/experimentation and likely some performance degradation from the original circuit.

The LDR/LED technique has the advantage that the control and signal circuits are completely isolated. If you mount the LDR in the effect you can have longer leads to the control circuit. Capt'n, the concept youve devised requires running wires between digipots and effects. High impedance parts of the circuit that are not intended to be connected to wires will mean that bad noise is highly probable. In fact the noise your experiencing now is probably masking the underlying digital noise. If you only want patch change then ok(as you point out). Digipots are not isolated and therefore must be connected (dc coupled) you may be better of with the digipot ground actually connected to analog signal ground (and connect the shields of your wires to this ground!). Just make sure the voltage rails of the bigmuff are less than the voltage of the digipots bias rail(s). The ones I used were dallas semi and had +/- 5V bias inputs so I was able to control parametric filters with +/- 5V split rail. You should be able to run your bigmuff off 5V no problem. I haven't seen the datasheet of your digipot so this is just general advice.

Yes Capt'n, the bigmuff circuit has a lot of gain so noise will be an issue regardless of control method. Seperate boards is probably not the best in this case. However, you should be able to improve it Sheilding and elimination ground loops is a must to minimize hum. The problems I had were definely digital signals. If you stop data to the digipots does the noise reduce?

Ok, I had a look at the Ross Phaser circuit and have also located the article that I used for my previous experiments. http://graffiti.virgin.net/ljmayes.mal/comp/vcr.htm As you see in the article the simplest application involves 2 resitors and FET but one side of the "variable resistor" is connected to ground. this is ok, because many circuits function with one side of pots connected to ground eg vol pot.  It would be possible using an op amp to implement a floating ground that would create a more general "varaible resistance" but it would add some complexity. Back to the Ross Phasor the "recycle" pot is grounded so the simple FET resistor can be used in conjunction with a fixed resistor to control regen via CV. Interestingly, the phasor itself uses a very similar FET configuration to control the characteristics of filter stages. An internal CV is generated to modulate these. U4B is an LFO which provides this CV. My recomendation is to inject a MIOS CV at this point in the circuit  ie. at RV4 and delete the LFO from the assembly. FETs work and sound great for instrument effects (they exhibit subtle distortion similar to valve). However for general mixing application they probably lack fidelity. Automation is a challange for analog circuits of you want pristine audio. Logarithmic motor faders could be used for volume and linear ones for pan and eq but it starts to get expensive and complex (how many MIOS cores would you need?). Digipots do not have any noise if there is no digital data be transmitted through their shift registers. It may be possible to transmit data to them to implement a "program change" or "scene change" concept. In between  changes there would be no digital noise. Digipots also exhibit nonlinearity which would make the purist audiophile cringe (does this really apply to instrument effects and synths?). cheers [edit] The reason for replacing the internal LFO by a MIOS derived CV is that it would allow for tempo synced sweep and other complex behavour of the phasing sweep. (It also makes the circuit a bit simpler!)

hi guys, one problem with using digipots for effects can be the digital noise getting into the signal if there is some signal gain involved (usually the case). Another approach is to use a CV to bias a FET transistor to achieve a variable resistance! This is done with a couple of resistors an a low cost feild effect transistor. It should be straight forward to use analog techniques to provide taper characteristics other than linear (another limitation of digipots). Let me know if this sounds interesting to you, I may be able to find some links again (its been a while since I experimented with this). cheers

Its a great product concept (ignoring the inevitable price tag)!

hi, make sure you use the primary bootloader for MIOS upgrade (begin upload within 2 secs of poweron/reset) cheers

hi, make sure you use the primary bootloader for MIOS upgrade (begin upload within 2 secs of poweron/reset) cheers

The different H/W formats is a great thing! I like the Tiny option because it will allow me to trial the application and see if I like the workflow as a way of making music before I go ballistic and build a dedicated one. Thorsten, will it be possible to edit in real time using the Tiny plus Java applet?

hi pay_c, (I hope) you have looked at cs_m_display.inc for the example of adding a display page. The code I wrote was some months ago and I'm now a bit rusty on the details now. You really need to look at what Thorsten does to achieve what the existing display pages do (mine is neccessarily more complex) . I take it that what you want is simply what the original MB64 did and that is provide a bar graph for each of the 64 pots at once. If memory serves me: MB64_POT_VALUES_00 is the RAM location of the first pot value so that (MB64_POT_VALUES_00 + 63) is the value of pot 64. Use the variable MB64_LAST_POT0 to get the address of the most recent changing pot. (you dont want to update all 64 every time!) Like I said, get familiar with what Thorsten has written before trying to write/add code yourself! (this will save you much grief, however it is hard work and not that fun, it is the only way to learn properly, it will be quicker in the long run). cheers!

Hi Ryan, I'm maxed out completing another midibox design project so I can only help with the broad approach. Some basic electronic interfacing/diagnostic skill is required. 1) keep looking for theremin projects (when I last looked there were very many!) Some will be much easier to build than others. Find the easiest (to start with) 2) Theremin outputs an audiowave of varying freq and amplitude. If you dont want huge accuracy for pitch (what you described) devise a FV circuit that outputs a DC voltage of 0-5V (using LM2907?), [There are hobby kits that use a low cost FV converter IC this is where I would look first, in choosing a device] For amplitude a level detector/recitifer with max output of 5V (using common op amp). Like I said, electronic skills are required, however a very elegant, low cost implementation is absolutly do-able! cheers

Hi Thorsten,others, Yes, I think what youve observed is the fact that signal coupling deteriorates with distance, not a good means of distance measurement! I'm sure there are some very effective ways of doing this (measuring distance) that are easy to implement. To the original poster, Ryan, what is your interest in this? If it is oriented to a musical instrument type controller have a look (via google) at Theremin (spelling?). Such instruments could be interfaced to midibox using frequency to voltage coverter IC's for pitch and amplitude detectors for velocity. Post back if you find something interesting as this is something I have thought about in the past. Also a highly accurate determination of pitch can be achieved using the onboard PIC CCP modules (upt o 16 bit accuracy,2 channels). cheers

Have you looked at modifying the target circuit (effect) to function with a different resistance? This is almost always possible. Also, from experience much care has to be taken to avoid noise coupling from the digital to analog parts of the circuit especially if there is signal gain involved. This is more of a problem when the digipot is being continuously updated than if the setting is only changed with each "patch". cheers

hi, I used H11L1 on my midibox but I had to bend/stretch the leads to make the correct pinout. You will need to lookup the datasheet for details on the correct connections to make. The opto I used was spec for 1Mbit/s so I new it would be fast enough. cheers

Clearly you don't think this is a very good idea. No, actually a complete parts list is a good idea and it would be useful to others, so why not do it yourself? ;) Instead I will go the route I hoped to avoid, asking 1 billion questions that have probably been asked time and time again till I get enough info to build my basic controller. Please make use of the forum search and other midibox web resources first, then if you still don't understand then please ask questions. good luck with your project

The basic procedure is to consider the modules required for the configuration you want to build and locate the parts on the schematics. If you would like to submit the list you make when you build yours (to Thorsten and/or the portal), then this will be of benefit to the midibox community. cheers

hi Dusty, The various configurations, very well documented with pretty much all you have requested already exists at uCApp.de. My advice is to build one of the known documented designs as a first step. Yes, there is total customisation possible but there is too much to learn/know in one step. The published designs offer hugh flexibility as control surfaces/midi instruments. How you work with your control surface is also an evolving thing that will develop as will your ideas about what you want. So my best advice is to go with one of the standard configurations and use it to learn!

Hi, The use of optical mouse is really clever! There should be no particular problem with latency, however addition of mouse decoding will not be included now, but perhaps in the future. The source code may be available with the release. cheers

Hi, Progress has been made on the PC/AT Keyboard decoder. A design and firmware will be released to the midibox community in the next few weeks: Features in development: 1) MIOS interface. IIC 2wire bus interface to MIOS core host. 2) Midiout for use as standalone kbd-midi adaptor. Possible features for subsequent firmware updates:- Alternative key mappings with on-the-fly user selection for: - different key layouts (exotic European variants) - different midiout mappings 3) Midi merger (just insert adpator in midi chain with other control surface/s) Options (1) and (2) will definetly be included in the first release. Two hardware configurations are being documented: -MBHP Core module using PIC16F877 -a custom "mini-core" optimised (for size and construction effort) just for this application using PIC16F876. Both will use the same firmware. The firmware for this project is based on foundation programs by Thorsten and others (who will be credited in the release). I making this post just to let users know of the substantial progress and in light of alternatives being offered. cheers

I used SIL plugs and sockets on my MB64 and the cost was considerable. I did some work on my box since I built it but I dont think Ive ever had to disconnect modules. A cheaper (and quicker, I think) way is to mount single 1mm PCB pins (cheap in bulk) to the pcb. Then get your ribbon, strip, tin and solder to the pins. The result can be very neat, and it's quick and can undone and redone just as easily. cheers

John, I'm glad you've said it because no one else seems to have expressed this (that I have noticed). Yes, MIOS and 18F is a fantastically productive firmware development environment!!!!! cheers

I was also wondering if one can find pots that spin and spin around, resetting on every lap(cool for scratching). My suggestion is to use a rotary encoder and alter the output in firmware (if your up for some code tweeking ;)). I dont know anything about scratching but using this method you could come up with many more taper patterns than just wrap around. A recent post regarding reversing the direction of an encoder provides clues as to where to do the manipulation. cheers

Yes, the MidiO128 was designed for such applications. (see MIDIO128/Design at ucApps.de) cheers

The keyboard adpator I'm planning at the moment is to accept serial data from a standard PC AT Qwerty and convert it into IIC slave interface for connection to a MIOS core. It will be based on the low cost PIC16F84 (18pin device), programmable from a JDM. Once constructed it is unlikely that the firmware will ever need change. All user options and functionality are provided by the MIOS Midibox it is connected to. If someother exotic keydevice is wanted, I suggest to cut tracks(!) and wire keyboard switches to DIN module(s). I'll be oherwise very busy for a few weeks, then I expect to implement it quickly. I'll post back here when more news. cheers

I'm currently planning a low cost, high availability implementation that will suit most users and be easily adaptable for variations. cheers