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79 lines
2.3 KiB
79 lines
2.3 KiB
3 years ago
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# USB GPIO
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Simplest USB GPIO output with Arduino Pro Micro.
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There is no input function. It can be easily added, but I didn't need it.
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## How to use it
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The device appears as a USB-serial ttyACMx. Write characters to it. Everything works in character mode.
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There's no harm in sending CRLF, these are discarded with no reply.
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- Uppercase letters turn GPIOs on, their lowercase counterparts turn them on.
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- Valid commands return the same character back. Unknown commands return "?".
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- "0" turns all *off*, "1" turns all *on*. This is handy if you need just one signal, or want to shut everything down.
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Mapping - see the X-table in main.c
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GPIOs on the pro micro board are like so:
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```
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A D3 ---(usb)--- raw
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B D2 gnd
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gnd rst
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gnd vcc
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C D1 F4 R
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D D0 F5 Q
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E D4 F6 P
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F C6 F7 O
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G C7 B1 N
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H E6 B3 M
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I B4 B2 L
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J B5 ------------ B6 K
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top view
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```
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The left LED blinks on activity, right LED blinks with ~5s interval to indicate operation.
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## Hardware connections
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Hook this up to a SSR or LEDs or whatever that needs switching on and off. All GPIOs on the board are accessible.
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Remember: Max current per pin is 10mA, max total current is 150mA. It can take a bit more, but it's not recommended.
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Use transistors or driver IC if needed.
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## Building
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This is a firmware for Arduino Pro Micro ("Leonardo"), using ATMEGA32U4.
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It can be ported to any AVR that's supported by LUFA.
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To compile it, download the LUFA library and update LUFA_PATH in Makefile.
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- https://github.com/abcminiuser/lufa
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- www.lufa-lib.org
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The exact version I used is 2021-01-30: http://www.github.com/abcminiuser/lufa/archive/LUFA-210130.zip
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Run "make all" to build everything, or "make hex" to build only the elf and hex.
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## Flashing
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use avr-gcc and avrdude, flash with "make flash".
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### How to enter bootloader
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This board is old and dumb, there is no reset button and the bootloader often fails to start.
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To go into BOOT, tap the RST button twice (if there is a button), or touch a wire from GND to RST twice within a second.
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I don't know how this works, maybe the bootloader disables the reset function temporarily.
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This trick sometimes doesn't work. Also, there is a timeout, then it exits bootloader by itself.
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