[sdiy] OT? MIDI to RS232 converter box?

rsdio at audiobanshee.com rsdio at audiobanshee.com
Sun Jan 21 02:27:59 CET 2018

"Sleepy Dog" Steve has a good point: Take advantage of the USB Serial Driver to run at the MIDI baud rate.

The problem with the circular buffer method is that it’s possible to overrun the system in one direction - the higher baud rate could overwhelm the MIDI side. Of course, if your adaptor is only going in one direction (from MIDI to a higher baud rate) then this particular risk is a moot point.

All things considered, you’re most likely to find a solution with the least effort if you can find a USB Serial Device that supports the MIDI baud rate.


On Jan 20, 2018, at 10:53 AM, sleepy_dog at gmx.de wrote:
>> other baud rates and/or USB virtual serial would be fine
> wouldn't just any ft232 or so based little board off ebay do, if you tack on a buffer, opto isolator or what ever is needed?
> If different baud rates do work, then why not us such a virtual COM port thing and
> operate it at the exact MIDI baud rate - no byte FIFO'ing in between needed.
> I think even the cheaper ft232 do support to set that baud rate (I'm sure I did that), up).
> There are even some fractional parts that can be added to an integer divider to set the baud rate,
> but for 31250, it would be integer divider of 1536 from 48 MHz clock:
> http://www.ftdichip.com/Support/Documents/AppNotes/AN232B-05_BaudRates.pdf
> But not every other of those virtual com chips do. E.g. the cp2103 does *not* (just looked it up, can only do certain fixed standard baud rates)
> This plus the very manageable mentioned external electronics?
> https://www.ebay.com/itm/FT232-USB-UART-Board-Type-A-FT232R-to-RS232-RS485-Serial-Converter-Module-Kit/261119068830
> - Steve
> Am 20.01.2018 um 19:30 schrieb MTG:
>> I'm looking to BUY a "simple" converter box that takes 5-pin DIN MIDI at one end and on the other true DB-9 serial (at say 38.4kbaud). So this would entail a microcontroller with a couple of circular buffers and 2 UARTs. NOT just a level-shifter-to-current-loop thing.
>> I don't really want to build it from scratch if I don't have to. I don't want any other intelligence, but other baud rates and/or USB virtual serial would be fine. All I can see online is a $600 box and a bunch of etch-your-own board PIC kits. Oh and some DMX ones, but not sure about them.
>> Reason: to run an old EPROM monitor in an old synth. The monitor utilizes the existing physical layer of 5-pin DIN MIDI, but on the host side the monitor is operated via a COM Port Terminal program like TeraTerm.
>> I would have thought there were at least some old half-baked solutions for people that didn't want to pony up the big bucks for a MPU-401.

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