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2.The process supports design scales of 300 devices or 1000 pads

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2.Smooth support for design sizes of over 30,000 devices or 100,000 pads

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STD Smart MIDI box

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License: CC-BY 3.0

Creation time: 2020-01-25 05:08:03
Update time: 2021-04-07 03:40:18
(still work in progress, not fully tested) A smart MIDI box based on a STM32 "blue pill" microcontroller (STM32F103C8T6). Software is hosted on Github: https://github.com/retro16/MidiBox Uses a HD44780 16x2 LCD screen with the usual I2C converter. The interface is made of 4 push buttons arranged in a directional pad (up, down, left, right). A SD card can be attached for more features. Optional parts -------------- Some parts on the PCB are optional, depending on what you wish to do with the board. * To remove MIDI IN 1, omit R1, R2, D1 and U1. * To remove MIDI OUT 1, omit R3, R4, R5, R6, Q1 and Q2. * To remove MIDI IN 2, omit R7, R8, D2 and U3. * To remove MIDI OUT 2, omit R9, R10, R11, R12, Q3 and Q4. ### Optional SD, LCD and buttons. If you remove the SD card, the LCD screen and buttons, all MIDI messages will be routed to the first MIDI output. It acts like a buffered MIDI merger. MIDI port extenders can be used in that configuration. Building a multiplexed extender ------------------------------- * Build the same PCB as the main board * Omit SD, LCD and buttons as they are unused * Place a jumper on EXT (or link LT and RT pins together). * Set AH and AM to either open or closed to select the 2 MIDI ports it will route (use 0 ohm 0805 resistors or just solder a piece of wire between the pads). Each extender must have a different AH/AM combination. * Connect "EXT TX" of the main board to "EXT RX" of the extender * Connect "EXT TX" of the extender to "EXT RX" of the next extender, and so on and so forth (up to 4 extenders, order is not important) * Connect "EXT TX" of the last extender to "EXT RX" of the main board
Design Drawing
schematic diagram
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1 /
ID Name Designator Footprint Quantity
1 POWER P1 HDR-TH_2P-P2.54-V-M 1
2 MUX P2 HDR-TH_2P-P2.54-V-M 1
3 1N4448 D1,D2 DO-35 2
4 BC547B Q1,Q2,Q3,Q4 TO-92_3PIN-L4.95-W3.94-PITCH2.54-L 4
5 MIDI1 IN H2 HDR-TH_3P-P2.54-V 1
6 MIDI1 OUT H4 HDR-TH_3P-P2.54-V 1
7 MIDI2 IN H5 HDR-TH_3P-P2.54-V 1
8 MIDI2 OUT H6 HDR-TH_3P-P2.54-V 1
9 100u C1 1206 1
10 BTN H1 HDR-5X1/2.54 1
11 6N137EE U1,U3 DIP8 2
12 BluePill P5 BLUEPILL 1
13 LCD H3 DIP-1X4P2.54 1
14 100n C2 0805 1
15 SD P4 HDR-8X1/2.54 1
16 MIDI UART H7 HDR-F-2.54_1X4 1
17 10k R3,R1,R6,R9,R7,R12 0805 6
18 220 R2,R4,R5,R8,R10,R11 0805 6
19 ADDR_H J1 0805 1
20 ADDR_M J2 0805 1
21 EXT_EN J3 0805 1


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