ATMega 32u4 standalone pins

Other Hardware 3rd Party Boards
1

im currently making a custom pcb with a 32u4 as the controller, which i migrated over from a pro micro. when i look at the schematic of the pro micro, i see that digital pins 11-13 are marked as "not used", but it seems they still have a designation in the arduino ide (i think). can i use these pins for my project or will these pins be inaccesible because im using the pro micro bootloader?

2

If the pins are not currently selectable, you can look at boards.txt and the version of pins_arduino.h to see how the pins are created and modify it to add them in.

3

CrossRoads:
If the pins are not currently selectable, you can look at boards.txt and the version of pins_arduino.h to see how the pins are created and modify it to add them in.

i am going to be completely honest here and say that i understood maybe half of that

4

The ATMega32u4 is the basis of the Leonardo, which has support for pins 11-13. I can't see why they wouldn't be available if you're making your own board and you route them out. I don't know the history of the Pro Micro but I assume they tried to keep the form factor of the pro mini which uses the ATmega328. Since the ATmega328 has 32 pins and the ATMega32u4 has 44, a few pins had to go if they wanted to keep the same form factor and header spacings.

5

Here is the boards.txt entry for the Leonardo:

##############################################################


leonardo.name=Arduino Leonardo
leonardo.vid.0=0x2341
leonardo.pid.0=0x0036
leonardo.vid.1=0x2341
leonardo.pid.1=0x8036
leonardo.vid.2=0x2A03
leonardo.pid.2=0x0036
leonardo.vid.3=0x2A03
leonardo.pid.3=0x8036


leonardo.upload.tool=avrdude
leonardo.upload.protocol=avr109
leonardo.upload.maximum_size=28672
leonardo.upload.maximum_data_size=2560
leonardo.upload.speed=57600
leonardo.upload.disable_flushing=true
leonardo.upload.use_1200bps_touch=true
leonardo.upload.wait_for_upload_port=true


leonardo.bootloader.tool=avrdude
leonardo.bootloader.low_fuses=0xff
leonardo.bootloader.high_fuses=0xd8
leonardo.bootloader.extended_fuses=0xcb
leonardo.bootloader.file=caterina/Caterina-Leonardo.hex
leonardo.bootloader.unlock_bits=0x3F
leonardo.bootloader.lock_bits=0x2F


leonardo.build.mcu=atmega32u4
leonardo.build.f_cpu=16000000L
leonardo.build.vid=0x2341
leonardo.build.pid=0x8036
leonardo.build.usb_product="Arduino Leonardo"
leonardo.build.board=AVR_LEONARDO
leonardo.build.core=arduino
leonardo.build.variant=leonardo
leonardo.build.extra_flags={build.usb_flags}

You can see the build variant is "leonardo"
These are the pins to names from the variant/leonardo/pins_ardiuno.h:

const uint8_t PROGMEM digital_pin_to_port_PGM[] = {
	PD, // D0 - PD2
	PD, // D1 - PD3
	PD, // D2 - PD1
	PD, // D3 - PD0
	PD, // D4 - PD4
	PC, // D5 - PC6
	PD, // D6 - PD7
	PE, // D7 - PE6
	
	PB, // D8 - PB4
	PB, // D9 - PB5
	PB, // D10 - PB6
	PB, // D11 - PB7
	PD, // D12 - PD6
	PC, // D13 - PC7
	
	PB,  // D14 - MISO - PB3
	PB,  // D15 - SCK - PB1
	PB,  // D16 - MOSI - PB2
	PB,  // D17 - SS - PB0
	
	PF, // D18 - A0 - PF7
	PF, // D19 - A1 - PF6
	PF, // D20 - A2 - PF5
	PF, // D21 - A3 - PF4
	PF, // D22 - A4 - PF1
	PF, // D23 - A5 - PF0
	
	PD, // D24 / D4 - A6 - PD4
	PD, // D25 / D6 - A7 - PD7
	PB, // D26 / D8 - A8 - PB4
	PB, // D27 / D9 - A9 - PB5
	PB, // D28 / D10 - A10 - PB6
	PD, // D29 / D12 - A11 - PD6
	PD, // D30 / TX Led - PD5
};

Is it missing pins? The file can be modified and the missing pins added. They need to be described in several places in the file to fully document them.