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widdly

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Posts posted by widdly

  2. Pull down resistors for banana plug inputs to AIN

    in MIDIfication

    Posted

    I am building a module that takes an analog CV and converts it to a midi message.  I am connecting the CV via a 1K resistor to an AIN input with  a diode clamp to protect against over/under voltage.  

     

    I am using Banana cables so when no signal is connected the AIN inputs are floating and will produce randon results.  My solution is to connect a 1M resistor to GND on each input.  Is this the correct way of doing this?  

     

    My other question is with regards to the schematic here...  http://www.ucapps.de/midibox_ext/lfo/lfo_schematic.pdf

    The diode clamp is using 1n4148 diodes so the PIC pin will get -0.7 to 5.7.   But the datasheet quotes -0.3 to 5.3 as being safe.  Is it ok to use 1n4148 with a PIC or would it be better to use a BAT48 or similar that would limit the voltage closer to the datasheet range?

  3. MIDIbox CV V2 Concept

    in MIDIfication

    Posted · Edited by widdly

    Another beginners question (sorry if I get annoying) .. but would a CTRLR Panel be an alternative for non-iPad users??

    The newer versions seem to support NRPN better than the older one ... 

    If yes .. I would be willing to invest some time in this stuff ... 

     

     

    Lemur is out on Android now.   :smile:

    • Like 1

  7. USB Host?

    in MIDIbox SEQ

    Posted · Edited by widdly

    Unfortunately it's in japanese but this site is the one I was thinking of. It's based of the USBhostlite examples.

    http://www.rjblog.net/archives/2009/e000331.php

    translated...

    http://translate.google.com.sg/translate?hl=en&sl=ja&u=http://www.rjblog.net/archives/2009/e000331.php&ei=K5S8TtuDMKWH4gTO_ISABA&sa=X&oi=translate&ct=result&resnum=1&ved=0CB8Q7gEwAA&prev=/search%3Fq%3Dhttp://www.rjblog.net/archives/2009/e000331.php%26hl%3Den%26biw%3D1366%26bih%3D704%26prmd%3Dimvns

    There is source code included. The source code has a parser for the usb descriptors, checking if they are audio devices with midi streaming. Usbhostlite has an interrupt and a blocking function Host_ProcessTD that fills a buffer from the USB port. Other than the first byte, the buffer is written straight to a serial midi port. The example doesn't have any hotplugging implementation other than exiting if the midi usb is disconnected.

    There is a description of the first byte content in the USB midi spec, on page 16...

    http://www.usb.org/developers/devclass_docs/midi10.pdf

    I'm not sure on the hardware side but perhaps this post might be helpful in setting up the physical USB host port on the LPC1768...

    http://knowledgebase.nxp.com/showthread.php?t=2064

    I would think class compliant USB-midi support would be the way to go. I imagine support for custom stuff would be a nightmare. Although support for the novation launchpad would be a neat way to add a BLM without all the soldering.

    edit..

    Actually looking more closely at the code from the japanese site, it doesn't look quite right. The MIDI_ParseConfiguration function is never called. I'm guessing he must have modified the usbhostlite function Host_EnumDev to call MIDI_ParseConfiguration instead of MS_ParseConfiguration.

  8. USB Host?

    in MIDIbox SEQ

    Posted

    Is it possible to add USB host support on the LPC17? I've seen some other LPC based projects on the web that have midi usb host features.

    I think the seq4lite would be great with one of those usb only mini keyboards like the akai lpk25.

  9. question about FM

    in MIDIbox FM

    Posted · Edited by widdly

    The midiboxFM is a very different synth to the FM8 despite both being FM.

    The things labelled A-B-C-D-E-F in the FM8 square matrix thing on the advanced page are the operators. It's like an oscillator and an envelope combined. The matrix in FM8 lets you setup any combination of Operators you want where as the OPL3 has only 4 preset routings. FM8 also has a filter and a wave shaper ( G and H on the matrix). FM8 envelopes are very sophisticated, they have unlimited breakpoints, tempo sync and can be used as LFO's as well as operators. Additionally there are two tempo synce LFO's in FM8.

    The OPL3 built in envelopes are quite limited with only a small range for the adjustments. TK has implemented an additional Envelope and two LFO's in the MidiboxFM which can tempo sync. The MidiboxFM has a wavetable sequencer that is pretty unique and doesn't have an equivalent on the FM8.

    I like the Midibox FM for bass sounds (similiar to the famous lately bass), percussion clicks and blips and for weird fx. I wouldn't use it for e-piano sounds because of the 4ops and limited op ratios. Pads and soundscapes are do able and they tend to sound lofi and glitchy.

  10. controlling Doepfer DIY synth

    in Design Concepts

    Posted · Edited by widdly

    Getting the CV's in the range 0-5 involves using a voltage divider (2 resistors). The problem with the Doepfer is that the ADSR, LFO and the resonance in the filter are not voltage controlled.

    If I was doing this, I'd implement the modulation sources inside the Midibox and have the modulation matrix in digital. It would be a lot less electronics and would allow you to do cool stuff like midi sync on the LFO's.

    I'd go with 8 CV's out of the AOut NG controlling Osc1_Pitch, Osc1_PWM, Osc2_Pitch, Osc2_PWM, Osc2_Level, Cut, Res and Amplitude.

    You could use CMOS analog switches to control other parts. I like the DG series switches ..http://www.intersil.com/products/deviceinfo.asp?pn=DG411 You can use these to switch analogue signals using a DOUT pin.

    The different wave shapes of VCO's could be selected with one of these chips. The sync signals could be switched with these. The second VCO signal could be switched to mix with the VCO1 or to frequency modulate either VC01 or the VCF.

    You would need two VCO's, two VCA's, and a VCF.

    For the VCO's I'd look at the Hearn Morley ones here...http://sites.google.com/site/hearnmorley/synth-diy-resources or the prebuilt pcb's from here..http://mattsonminimodular.com/

  11. Can I Build My own combined MIDI merge and thru box.

    in Design Concepts

    Posted · Edited by widdly

    You could build a GM-5 interface since you have 5 devices it would be perfect. It's a 5 in/out usb midi interface that is cheaper than anything else out there. You can set it up so the midi port names match the devices they are connected too. So when you are using say Ableton Live you select "Roland JV-2080" instead of "midibox gm-5 port 2". It's pretty ace.

  15. The R resistor to ground in R-2R AOut LC

    in Design Concepts

    Posted · Edited by widdly

    Yes and no. The steps aren't equally spaced with 1R to ground, that's right. Every other step is a "bit higher". It does bring the benefit of being able to have different configurations (2x8 bits that are identical, 1x12 + 1x4 bits). If you don't need the options you can easily adjust the 2 resistors to ground to get equal steps.

    Couldn't you just add another R resistor between the ground and pin 1 and between the ground and pin 5? That way you could have both equal steps and different configurations.

  17. Assigning AOUT offset to the User2 button matrix knobs

    in MIDIbox FM

    Posted · Edited by widdly

    I'm building a midibox fm. I've got all the circuit and control surface built, working and sounding good but I want to add a pair of AOUT LC and a pair of filters.

    I'm planning on building the EMS diode ladder filters described here.. http://www.modular.fonik.de/Page37.html They have CV control of cutoff AND resonance so I think they should work nicely. I'm trying to incorporate these filters so the cutoff and resonance settings are completely saved with the patch and don't require any external potentiometers.

    I want to be able to tweak the cutoff and resonance from the v-pots so I figured I could remap the USER 2 v-pots to control the cutoff and resonance via the AOUT offset parameters.

    In cs_menu_tables.inc at line 420 I figure I should change it to something like...

    
;; USER2        Register (00=dummy)        |<-->|  max   print ix,         exec ix          parameter transfer

	CS_MENU_ENTRY	MBFM_AOUTx_OFFSET,	   "Cut1", 0x7f, PRINT_AOUTxOFFS, EXEC_SELPAR,     R2PP2R_AOUTxOFFS

	CS_MENU_ENTRY	MBFM_AOUTx_OFFSET,	   "Res1", 0x7f, PRINT_AOUTxOFFS, EXEC_SELPAR,     R2PP2R_AOUTxOFFS

	CS_MENU_ENTRY	MBFM_AOUTx_OFFSET,	   "Cut2", 0x7f, PRINT_AOUTxOFFS, EXEC_SELPAR,     R2PP2R_AOUTxOFFS

	CS_MENU_ENTRY	MBFM_AOUTx_OFFSET,	   "Res2", 0x7f, PRINT_AOUTxOFFS, EXEC_SELPAR,     R2PP2R_AOUTxOFFS

    ...but I'm not sure if this will work as I expect. Will the v-pots control AOUT 1-4 offsets respectively or just control the same offset of whatever AOUT is selected in the AOUT menu?

    Is there another way of mapping this?

  18. GM5 powering core, din, dout and 64 leds

    in Design Concepts

    Posted

    Thanks for the reply.

    I thought the LED's would draw less current since they are wired in a matrix with the shift registers so they are not actually all turned on at the same time. When it's running I figure only 8 LED's will be turned on at any moment. I suppose the situation will be different at power up before the shift registers are set up by the PIC.

  20. MBHP_4066 (16 bilateral switches)

    in MIDIbox User Projects

    Posted · Edited by widdly

    I don't know how these would go switching the negative cycle of audio signals. Normally when switching audio with a 4066, a DC bias is added to the input so the negative voltage is higher than the negative supply of the 4066.

    If you wanted to use larger audio signals like in a modular synth I'd try the DG211 chip instead. You would need a bipolar power supply though.

  22. GM5 Driver for Windows

    in Latest News

    Posted

    No it's not.  The FAQ describes how to get Windows to recognize two different GM5 boards by using a different number of ports or changing the PID link.

    It doesn't describe how to use two different modified .inf files to get 10 custom device names.  I'm not sure that would work with the ploytec driver installation since it seems to remove previous instances of the driver.  I think I could probably install the two devices then modify the names in the registry.

    I guess there is only one way to find out if it will work .  I'll report back when I finish my second board.

  23. GM5 Driver for Windows

    in Latest News

    Posted

    Question on device names with multiple gm5's.

    If I modify the .inf I can have the names I want for devices.

    Now lets say I build my second gm5 with 5 ports and I cut the jumper so it uses the ploytec PID.  Can I modify the .inf file again to get 5 different names?  Will I need to modify PID in the .inf as well?  Anyone tried this?

    Or would I be better off building the second gm5 with four ports?  How would that work when installing the driver with the modified .inf file?  I would have thought after installing the first gm5, the driver would auto detect when the second one is plugged in.

  24. GM5 Driver for Windows

    in Latest News

    Posted

    Awesome,  this is great.

    Multiclient was the one missing feature that was driving me mad.  Now I can have my synth editors and Ableton running at once which will totally change my work flow.

    I'd had no trouble with huge sysex dumps on the stock ms drivers.  I'd tried doing it simultaneously on multiple ports without any problems.

  25. GM5: Least-cost USB-MIDI Interface Chip for 4.50 EUR

    in Bulk Orders

    Posted

    Finished my 5x5 interface on the weekend.  It worked first time whooot!!

    I soldered 10 midi cables.....never again.  Take TK's advice and buy some cheap ones instead.  I used a plastic case and mounted those metal panel mount sockets on the front.  It all sits around the back of my rack so need for it to be pretty.  Now every one of my rack units has an individual in/out. 

    Thanks ploytec and TK. 

    One question, is the firmware in the GM5 upgradable or is it masked?  I'm wondering if a fix for the device names from eprom is feasible.

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