funkyboard

Hi Guys - I am VERY impressed with your work on this project so far. Wow! I was wondering if you know how it would be possible to reduce the latency. One of the great things about hardware samplers is that they can achieve much lower latency compared to software. I have a few ideas of how this could be done: 1. First obviously we'd have to reduce the I2S DMA buffer size 2. Second, we could implement a solution where the first X number of samples are preloaded into memory.. so that they can be played instantly while midibox asynchronously fetches the next chunk from the SD card, etc. #2 above is very similar to the DFD concept as used in the popular software sampler as per this page: http://www.native-instruments.com/en/support/knowledge-base/show/58/what-is-dfd/ I believe it could even allow us to use larger samplers and achieve higher polyphony! I wish I knew how to implement this myself, but I am afraid it is beyond my expertise. My dream would be to have as low as 1 ms of latency... as a keyboard player this would be amazing. Anybody know how to do this?

Hey moogah, there are chips such as the MAX3107 and MAX3100 (or NXP has some dual channel ones which are more economical but slightly more elaborate to program). These allow you to "bit bang" serial UART communication (in this case each MAX310* ==> 1 x bidirectional MIDI In/Out). Part of what makes this possible is the built-in FIFOs on these UART chips. It means you don't need to use up dedicated UART peripherals in the MIDIBox hardware... of course you would have to write some custom code to drive these chips, but once that's done, it would be really easy to add many ports (probably even more than 16!) since MIDI is relatively slow compared to the LPC17 MIDIBox. As TK also mentioned, this could also be done purely in software of the LPC17 MIDIBox (without even using those UART chips) by cleverly writing an app for MIDIBox (again because LPC17 MIDIBox is fast and MIDI is slow), but the success of such a method will probably depend much more on clever programming (streaming approach, sampling-strategy for the the incoming serial) and might not be feasible (read: fast enough) if you're "super-router" has to do something more than a very basic routing of MIDI events. The UART chips can ease the processing burden to allow your app to spend more CPU calculating your MIDI routes instead of merely handling the raw serial communication. Either way, you'd need to write some code that I believe currently doesn't exist for MIDIBox. Hope this helps...

YAY! Great idea TK! I just added myself to the next potential order! I feel like notifying all the people that posted "I wanna be a happy fella" back in nILS's back in January (I was one of them but sadly never made it into the order)... Since I don't want to be too spammy about it, instead I kindly ask these people to add themselves on the new bulk order via the wiki if you're still interested in the amazing GM5 :) mazatta smrl harley89 ballpein KnoxY moogah digga Elektruck ErMangaver digga Tommy-boy

Hi TK, Thanks for your reply... you confirmed everything I suspected... If I'm going to use Windows 7 64bit and want multiple MIDI pipes to my MIDIBox, I need a GM5, which has sadly disappeared :)

Yes, from a hardware perspective, expanding to very many UART peripherals is easy enough with added ICs from Maxim or NXP... I guess my question is more aimed towards the latency/speed (especially using multiple virtual ports with windows over a aingle USB cable to a single MIDIBox application using the port internally). The reason I'm asking is because according to this page, when using Window's built-in midi driver with a multi-port interface (such as the GM5, or in my case, the MIDIBox), the bandwidth of each port is bottle-necked to 1 ms between events... Maybe the Ploytec drivers can be used by the LPC17 core MIDIBox? :)

Hey Guys, now that there are no longer any GM5 chips available in small quantities, I was just wondering if anybody has experienced how the LPC17 core performs in comparison in terms of latency (with built-in Windows drivers for example)? I'm talking about the MIDIBox in USB MIDI mode of course... I believe it is even possible to enable 5-in/5-out on the LPC17 core with simple configuration flags. Any thoughts? Cheers from Montreal!

Received here too! Thanks TK!

I'm sorry to hear about that nILS, and thank you to TK for handling the bulk order. @mirmidi : Many of us added ourselves to a list of "happy fellas" as recommended by nILS when he closed the wiki page back in January: I'm crossing my fingers that there will be enough of those juicy GM5s for all midiboxers ;)

For people who didn't know they existed, it looks like Bourns has LED backlit rotary encoders! The tri-colour version is PEL12T which is pretty cool. I believe these would work GREAT with the transparent knobs if they fit... Attached is a screenshot of the datasheet showing what they look like.

nILS - I would be interested if there are any left. Cheers from Montreal!