infest

i sorted it all out, my pots were log. :-\ now, dont EVER use log! only in special situations! reason: let's say a pot has a turning radius of 270 deg. in that turn resistance varies from 0 to 10K ohm. translated to midi signals, the digital range can be fom 0 to 127. now using a linear pot means that if i turn it by half of full turn radius (135 deg), the resistance will be about 5K ohm, and the midi value about 63. this means that the relation between the degrees turned and the resistance changed is linear, e.g. if turned by quarter (25% of full rotation, clockwise or counterclochwise from any position), the resistance changes by quarter (25%, + or -), and so the approx midi value (e.g. from 63 to 100). this pot will give most accurate representation of the "virtual" knob in an audio software - there will be no difference in ther positions trough all of the turning range. the log pot simulates logarythmic function in relation turn amount and resistance. the result will be that youll turn the pot by half, and the virtual pot will move just by few deg. and when turned further, the virtual knob will start to rotate faster than the "real" pot and theyll meet at 100% _________LINEAR________ ___________LOG_________ rotation : 25% : 50% : 75% : 100% : 25% : 50% : 75% : 100% resistance : 2,5K : 5K : 7,5K : 10K : 0,8K : 7,9K : 9K : 10K midi : 32 : 63 : 100 : 127 : 10 : 30 : 115 : 127 this means that the log one is more sensitive in the one turn area, and less sensitive in the other. the only thing i can think of using log pots is in example if you need to controll (lets say) volume, but in a such way that you need very fine adjustments allmost at the maximum of it, but allso be able to turn it down completley - in that situation the half knob turn area uses as fine adjustment, and the other for coarse adjustments. afcourse if you connect the power to the pot otherwise, fine adjustments will be at the 0 - 30% of the volume. oh yes, there are not 2 strict "fine" and "coarse" parts of turn area, but they blend at some point in the turning area. i hope everyone can get a hint how a log pot works now ;D also, is someone needs, the pots can be custom made to represent any function/relations you desire, but those cost bout 2000 EUR ;)

yah it crossed my mind that they might be log. i thought that they're just low quality. the local (and only!) store that has them are not quite the experts... thanx man

Hi all! finally finished my midibox64 and set it up. for financial purposes i bought only 2 pots in case nothing works and connected them to the AIN module. the pots & buttons work but the pot rotation is not linear to resistance, e.g. in knob values from 0-127 when the rotation is at half the pot value is like 10 and afther that it goes relatively liner up to the end but it freaks me out. i think that it's cause i use some cheap pots (1 EUR)? can somebody tell me what pots have a good linearity/price realtionship? afcourse 4 eur/piece is the top price, and that can be ordered via farnell or bought somewhere in the ex YU area? thank you

Many thanx for such a fast reply Thorsten & raphael! Ill first try to run the midibox without dout, to make shure it works :) thank god only AIN inputs have to be grounded. if everything passes well ill try to use my rusty c++ skills and try to make some fun with LEDs. if i figure out the base app that is :D

Hi all! I just started to build up my MB64 based on PIC18F. i browsed trough this forum and these things are still not clear to me: 1. the firmware: my box will probably look like 32 pots, 32 buttons, 32 leds i read it i s recommended to use MIOS. if i understand right i need to first program the bootstrap loader using a PIC programmator, and then the MIOS and an application using sysex midi upload tools, right? what app would be best suited for this? also it seems that ill have to ground all unconnected AIN , DIN and DOUT cables (missing pots, buttons, leds) 2. DOUT the leds can be assigned to any button/event, i suppose the default state is button pressed:led on, depressed:led off? my goal is to custom control the leds, eg. when pot#3 reaches state 127 led#12 lights up, or maybe toggle state leds. is this possible using software configs provided here or does it require heavy interventions in the assembler code of the app? thanx