Transcribe

transcribe hardware

this is the hardware section of transcribe - a project created to control panasonic video_mixers with midi.

BOM

CORRECTION FOR CIRCUIT V0.2 AND LOWER

if you have circuit revision 0.2 or lower then there is a mistake on the footprint of the dsub9 connector sorry (serial from the 3.5mm jack to ave55 works fine) follow the following steps to get serial from the dsub9 header on these boards:

• solder the DSUB9_HEADER onto the bottom of the board
• from here pins 2 and 3 need to be swapped
• cut both traces going to dsub (the traces going between and around c2)
• wire the other ends pin13 and pin14 of u2 to the pins on dsub. u2_pin13 to dusb_pion3 and u2_pin14 to dsub_pin2
• finally due to another error on the board IF you have placed the 3.5mm jack at J2 THEN you must have a stereo cable plugged into this to use the DSUB9 output (otherwise signal is grounded)

potential additional parts to add :

assemble guide :

• i soldered the resistors, capicitors, diodes and regulator first, then the ics(/sockets) and pin headers, then the jacks
• i used pin sockets to attach the pro-micro and usb host to board in detatchable way (helpful for debugging) but this is up to you

blah blah blah

IF USING USB_HOST_MIDI YOU MUST CUT A TRACE ON THE BOARD ! heres how - ...

the trace you need to cut is going into the resistor labelled 2.2k in the top corner near the usb socket

explaining the sections of transcribe

transcribe is based around an arduino micro controller. included in this circuit are a number of different ways to input midi and output serial. you can choose which sections to populate based on your personal requirements.

A - micro-conntroller - centre

this is the brain of the circuit and is required to make it do anything. i am using a sparkfun pro-micro 5v, which uses micro-usb as power. (it is likely this circuit will also work with an arduino nano - which will require a seperate version of the pcb - but watch this space)

B - rs232 serial - output(/input)

panasonic video mixers (and other older devices) use a different serial standard (RS232) to micro-controllers (ttl). in this section serial commands from the uC are level-shifted to be recongised by these devices. only obmit this section if you are not interested in controlling old (rs232) gear. the data is exposed on a 3.5mm TRS (stereo) jack; tip - input, ring - output, sleave - ground.

NOTE - although not used by the default firmware, the hardware also allows rs232 serial input, so this porject could be modified to also control something from old gear

C - serial midi - input(/output)

the uC (in A) can act as a USB midi device. this means it can be controlled by a USB midi host (such as a computer running abeton, or a raspberry pi). this section includes the additional circuity to also control it with serial-midi (often seen on older instruments with din5 type plugs)

NOTE - although din5 plugs are often used for connecting old gear with serial midi, these sockets can be bulky and sometimes difficult to find. for this reason newer gear supporting serial-midi often use TRS jacks - leaving the standard-conversion to cables. i would use 3.5mm TRS (stereo) also for midi in and out, with tip - midi data (din-pin4), ring - midi plus (din-pin5), sleave - unconnected (or include a switch to swap tip/ring...)

NOTE - although not used by the default firmware, the hardware also allows serial-midi output, so this project could be modified to also output serial midi

obmit this section if you are not interested in interfacing with 'old style' serial midi

D USB-midi HOST

the uC (in A) can act as a USB midi device. this means it can be controlled by a USB midi host (such as a computer running abeton, or a raspberry pi). this section includes additional circuitry to allow the uC to also act as a USB midi HOST. this means it can be controlled by a USB midi device such as a korg nanokontroller (or many other external usb-midi controllers/ gear). obmit this section if you are not interested in controlling from a usb-midi device

section summary

video-mixer controlling options:

• control rs232-mixer with usb-midi from host : A + B
• control rs232-mixer with serial-midi : A + B + C
• control rs232-mixer with usb-midi from device : A + B + D

some bonus converting options:

• convert usb-midi controller to serial midi : A + C + D
• convert rs232 commands to serial-midi : A + B + C
• use a ps3 controller to send serial-midi : A + C + D

build notes for v0_5

• decide on what sections you want to build (ie need to have A, probably you want to send out serial so also add B. do you want usb-midi ? then add D, do you want serial midi in/out ? then add C etc)
• also decide what kind of serial midi ins/out jack you want - old style din5 or new 3.5mm jack ?
• i started by placing and soldering the caps and resistors, then diodes and regulator (check orientation!)
• i like to solder in pin sockets for the pro-micro and usb-header part so they can be removed if i upgrage the circuit design - this is up to you -> will need to solder in the pins onto the pro-micro and usb-host shield if not already done. note the extra pin needed on host and the trace that needs to be cut!
• if using pin sockets do this next - when cutting the sockets to fit aim your wire cutters exactly on the adjacent socket (one more) than you need - this is to ensure the pin part doesnt fall out of the socket you need when cutting. you may need to bend u6 down abit to fit socket in
• now place the j9 pins (and two jumpers setting the serial pins on din9) and the ic/ic_sockets
• finally can solder on the interface parts - midi ins and outs, din9 and 3.5mm jacks
• note dont need to solder anything on for u5 pins - this is just exposing pins on the pro-micro so it can be reflashed incase of critical error flashing - dont need to place the euroheader either - this is just incase you want to give 5v from an existing europower rail (take care of orientation of the header if doing this)