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product:usb2ax:gpio

This is an old revision of the document!


USB2AX: GPIO and SPI

This is advanced stuff!

On the bottom of the PCB of the USB2AX are exposed 8 0.1“ pads. They provide access to 6 very useful pins of the ATmega and to ground.

Notice that ground is common between the USB plug, the MCU and the Dynamixel connector.

The three pads on the side of the board are useful to reset the board and to run the stock USB bootloader. This is very useful when developing a custom firmware: if you break the auto-update feature (or simply don't have one), you can always run the bootloader and upload another firmware.
It is recommended not to use these as GPIO unless you really know what you are doing.

  • GND - Ground
  • HWB - PD7, Hardware Boot (active low)
  • RST - PC1, DW, /RST - Reset (active low)

The pads under the Dynamixel connector give you 4 GPIOs or access to the ATmega's SPI hardware.

  • PB0 - PB0, PCINT0, /SS
  • PB1 - PB1, PCINT1, SCK
  • PB2 - PB2, PCINT2, MOSI, PDI
  • PB3 - PB3, PCINT3, MISO, PDO
  • GND - Ground

The ICSP programming interface uses the SPI pins but might also need access to VCC. In this case, carefully get VCC on the USB connector (see schematics).

product/usb2ax/gpio.1364861762.txt.gz · Last modified: 2013/04/02 02:16 by xevel