eurocards

[Paul Hesketh]

Hiya - not posted for a while, been way too busy with DIY oak parquet flooring, hobbies had to take a back seat for a while. Anyways, I've decided to change the way I assemble things, having constant frustration with fragile and crappy breadboard connections as well as enclosures, so eventually decided that eurocard format is the way to go. Found some excellent eurocard and backplane boards being produced by

https://www.martenelectric.cz/index.html

so have started using them as a sort of "breadboard plus". Here's the first works in progress





I'm using a backplane in a 60hp verotec enclosure, with DIN41612 connectors to essentially extend/breakout out the pins of the teensy (a 4.1 on this one)



with sockets on the board and pin headers solder bridged onto the 41612 connectors and sockets



This seems to work pretty well so far, and having potentially 96 connections, seems pretty well suited to further expansion. I looked at the doepfer eurorack format, obviously based on the same principles, but prefer the number of connections, increased depth for mounting boards/physical components and the room for me to get my fingers in on the eurocard.

The cards from martenelectric allow a pretty simple access to row C, giving 32 pin outs, although 1/2 are gnd/vcc, and 31/32 are gnd/vdd.

Apologies for the waffle, but my main question is:

is there a standard pin organisation that I should use for the backplane? If others are using this kind of format for teensys, it might be sensible to use the same pins on the connectors to enable pcbs to be made simpler. If there isn't a standard (I've just used fairly random pins from the teensy attached to random pins on the connector), is it worth coming up with one on this forum? If so, is it better to organise pins by pin number from say the teensy 4, or by type of connection (serial, SPI, CAN, audio, I2C etc) to make it easier to integrate different families of teensy or other devices? I'm not at this level yet, but I'm intrigued by the possibility of using interoperable expansion boards. I'm just a hobbyist, and I'm sure there are factors I haven't considered, so would appreciate the input of anyone that actually knows what they are doing.....

End point of what I'm trying to achieve for now is a modular MIDI controller rack, for VST plugins and instruments. Set up inserts/effects/instruments in DAW, have dedicated hardware controllers in rack. A sort of virtual 500 series, essentially, but by using a "master teensy" avoiding some of the problems of MIDI device recognition, namings and allocations.

If interested, the start of this project contains ILI9341 display, 3 axis joystick, 1 mechanical switch encoder, 1 optical encoder wired through a level shifter, SSD1306 OLED, MCP23017 (used for 8 LED button switches), 1 mechanical on/off switch, wired to the red wire of USB port to switch USB power off when using external PSU. I also put in an external SD card reader, but can't get that to work atm, teensy seems to shut down when I insert a card. Possibly just a cheap crap board...

Other issue I have is that I've had to use the adafruit GFX library for now - the SSD1306 doesn't seem to play nice with the _T3 library, it won't compile and I get "redefinition of adafruit_gfx_button", so I presume there's something in the OLED library thats very specific. The front panels are my first attempts at making my own, drawn in Easel, and cut with a vevor 3020 cnc router, 2 flute alu mill and 2mm alu sheet. Cut at 0.1mm per pass, at 85% on the speed control. Gets there in the end...can get away with 0.2mm a pass with a new bit, but try to go much faster and it breaks bits or stalls the motor, which then blows a line fuse in the power supply. Far from perfect, but useable and getting better. The bluebell 5V psu and verotec rack were bought off ebay. I was concerned that leaving the PSU wired into VCC but not turned on would cause problems when powering teensy from USB, but I'd guess that there's a "backfeed" relay on the PSU, as I can hear a small click when USB power applied.

Anyways, enough for now, I'd appreciate thoughts and opinions.

Paul.

 

[snowsh]

Paul,

I have a recording console from the late 80s that uses eurocard backpane connectors. Its was based on a z80 and follows that standard. I have attached the connector detail schematic for the backpane, it might help. BTW im just down the road in Falkirk...

I should note that Ax is a address line, not an anlogue line. But remember this was for Z80 architecture so dont feel you need to follow any of this. Maybe the power pins would be a reasonable standard to follow..

 

[Paul Hesketh]

Paul,

I have a recording console from the late 80s that uses eurocard backpane connectors. Its was based on a z80 and follows that standard. I have attached the connector detail schematic for the backpane, it might help. BTW im just down the road in Falkirk...View attachment 30995

I should note that Ax is a address line, not an anlogue line. But remember this was for Z80 architecture so dont feel you need to follow any of this. Maybe the power pins would be a reasonable standard to follow..

Aye, have found a couple of pinouts for this family of connectors when looking around, and agree that the gnd/power pin assigments seem to be pretty ubiquitous on the top and bottom 2 pins of each row on each 32 pin column of the 96 pin connectors. The backplane boards I bought from martenelectric additionally connect these to additional pins on the back as well, which makes attaching an external psu very straightforwards. Interesting that that pinout uses the next pin up for 12V, and lots more gnd pins, and it would certainly seem logical to have a separation of analogue and digital grounds. That STE seems a fairly sensible layout, easy to follow, and in future projects I will certainly need 12V as well as 5 and 3.3 - eg I plan to finish off building a balanced relay stepped attenuator preamp at some point. I've made a start, unbalanced atm, using a few fairly cheap 8 channel relay boards, switched using shift registers, and will eventually incorporate a balanced input selector. Those relays aren't the fastest, essentially twice a second is as fast as they can go, but still adequate for a hifi preamp or the basis of a midi controllable summing mixer. Currently use a BMC-2 as a monitor controller, fed from a marian seraph a3 soundcard, but this will hopefully replace that at some point. Always more things to think of than time to do them.....

Have noticed that most of the 100x160mm eurocard PCBs that are available tend to access row C easily, and some access row A, some on alternate numbered pins A and C, obviously for physical access on a single layer board, but not much touches row B. However, I've also noticed that those 3x32pin din 41612 connectors are the same size as dupont pins, and standard dupont cables will fit in the connectors, so still potentially usable.

As you've noticed, I live in Edinburgh, so hello there - its nice to come across someone reasonably local I have a hobby music studio setup - I don't really bother with recording, I just like to have everything wired up so that I can just play without having to faff around too much. Mainly interested in building dedicated controllers for things I use the most, vst plugins and vsti, as sometimes the technology just gets in the way of doing simple things easily, and can make it more of an intellectual process than an intuitive one. Sometimes I just want to simply move a knob, not have to wade through pages of options and multiple clicks. I'm not a professional musician, I just like to make a racket sometimes...

Anyways, thanks for the input, and take care.

Paul.