i_n_c_u_r

a r_e_c_u_r video sampler extension circuit - adding knobs, cv and serial midi control

this circuit is distributed by UNDERSCORES - an open video hardware label : it is available to purchase - as a pcb, kit or assembled unit - at underscores.shop
the schematic for the circuit can be found here
the pcb gerber files for the lastest version can be found here
interactive BOM is here
consider donating to the underscores project to help us continue creating for the commons

description

NOTE : i_n_c_u_r is an extension circuit for my existing raspberry pi project r_e_c_u_r - it will only be useful to you if you already have build a r_e_c_u_r

disclaimer: this is a fun custom project, but dont forget there are other ways to getting serial and cv control over recur parameters. USB midi is supported in recur without any extra circuitry. other diy and commercial products exist that convert cv to midi, and serial to USB. in my opinion a general solution for cv-to-usb-midi applied to recur is more useful than a specific board that only works with recur

4x knobs for physical control over shader parameters
4x cv jacks (0-5v) for sequenced control over shader parameters (from older/analog synths eg eurorack)
serial midi din5 jack for sequenced control over shader parameters (from older midi devices)
exposes rpi video output through rca jack (rather than the 3.5mm trrs jack on pi )
mounting holes and front facing interface parts for easier racking / enclosure building
interfacing with rpi through gpio leaving all usb jacks free

demo videos

documentation

this project is fully open-source hardware - all the files required to build it are included in this repo for free. if you have the time and/or skill you can contribute back by collaborating on / testing new designs, improving these docs, making demo videos/other creative content etc. you can also support the project financially by donating directing, or purchasing through the web shop.

depending on whether you are going fully diy or buying an assembled and tested unit, some of the following guides will be relavent to you. the flow would be:

ordering parts

parts sourcing guide (w/ notes on pcb fabracation ) - start here if you are building fully from scatch or have purchased a pcb

i try to source all the parts i can from either:

tayda ; cheaper for common parts like resistors etc, also good for mechanical parts like switches and buttons
mouser ; has lots more options, speciality video ic's, can sometimes cost more (free shipping on orders over 50euros)
other ; ocationally there will be parts which will need to be sourced elsewhere - usaully either aliexpress, ebay or amazon etc...

take a look at the full_bom for this project to see where i am sourcing each part from

import into tayda

go to the tayda quick order and in bottom corner choose add from file
select the file tayda_bom.csv in the BOM folder (you will have to download it first or clone this repo)
after importing select add to cart
NOTE: the minimum value for resistors is 10, so you may need to modify these values to add to cart (or if they are already modified here you will need to see the full_bom for actual part QTY)
OPTIONAL: it is a good idea to add some dip-ic sockets and 2.54pin headers/sockets to your tayda order if you dont have them around already

import into mouser

go to mouser bom tool and click upload spreadsheet
select the file mouser_bom.csv in this folder (you will have to download it first or clone this repo), then upload my spreadsheet and next
ensure that Mouser Part Number is selected in the dropdown above the first row, then next, process
if everything looks correct can now put add to basket

ordering pcbs

you can support this project by buying individual pcbs from the shop. if you would rather have pcbs fabricated from gerbers directly the file you need is here

i get my pcbs fabricated from jlcpcb - 5 is the minumum order per design
upload the zip file with the add gerber file button
the default settings are mostly fine - set the PCB Qty and PCB Color settings (you can check that the file looks correct with pcb veiwer)
it may be best to combine orders with other pcbs you want to have fab'd since the shipping can cost more than the items - also orginising group buys is a good way to distribute the extra pcbs /costs

i often use jlcpcb because they are reliable, cheap and give you an option of colours. remember though that the cheapest Chinese fab houses are not always the most ethical or environmently friendly - if you can afford it consider supporting local companies.

assembly guide

assembly guide - start here if you have purchased a diy kit

interactive BOM for build guiding

follow this link to view the interactive BOM

general solder advices

remember to heat pad first (2-3seconds), then add solder, then continue to heat (1-2seconds)
Checkout the web-comic soldering is easy for more soldering advice

general order of assembly

in general while assembling i start placing resistors and capacitors first. placing 5 - 10 components at a time and then flipping the board to solder them and trim the legs etc.
next i would do diodes, transistors and ic's - taking care that these are placed in the right direction (using a ic socket can be useful)
finally i place the interface parts - rca jacks, power jack, pots and switches - make sure these have lots of solder on for structural stablity

slightly more specific assembly advice

start with the lowest to place components : resistors, diodes, ic's

next i would place the two headers since soldering from the top can be awkward with too many components - NOTE these need to be placed upside down! ,:

J8 needs the pins facing up from top of pcb so the screen can go ontop and raspberry pi can go underneath
J6 also needs to soldered from the top so a jumper from the pi board can be run to bottom of circuit

finally place the pots and jacks.

rca video-out

if you want RCA video out from the pi on this pcb a jumper needs to be run from J6 to the composite video out on the raspberry pi board. on pi0 this is a labeled pin, however on pi3 you will need to solder directly to the board. i used a header-cable, cut one side to be soldered. The pin on pi3 is marked as PP24.

[picture coming soon]

operating guide

operating guide - start here if you have purchased an assembled unit

to enable the analog inputs ( knobs & cv ) go to user_input folder in r_e_c_u_r's _SETTINGS_ tab and toggle ANALOG_INPUT
to enable serial midi input go to user_input folder in r_e_c_u_r's _SETTINGS_ tab and toggle MIDI_INPUT to serial

for more info on operating r_e_c_u_r see this guide

more info

how the circuit works

contributing guide

if you would like to contribute back to these projects in some way but dont know how the best thing (for now) would be to reach out to me directly ( tim@cyberboy666.com or @cyberboy666 on scanlines forum) - i will be happy to help

community contributed enclosure designs:

an eurorack panel design by Simon Gorzelnik
a base enclosure by miles

credits & more info

This circuit is distributed through UNDERSCORES – open video hardware label – visit underscores.shop for more info

The pcb was designed using KICAD

Everything from gerbers, cad files, panels and documentation is freely available online and distributed under CC-BY-SA / open-source licenses – help us contribute to the commons !

Ask any questions or start discussions related to this project on the scanlines.xyz forum – an online community space dedicated to diy av / electronic media art

You can contact me directly at tim (at) cyberboy666 (dot) com Please get in touch if you are interested in hosting a workshop !

Thanks to Signal Culture for giving me the time and space to explore. to Bastien Lavaud for circuit advice, always. To Ben Caldwell for project advice. To everyone who has or will contribute ♥♥♥

cyberboy666/i_n_c_u_r