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Revision history


  • added Open hardware logo
  • added SW1 reset button
  • added D5 relay state LED indicator
  • added J16 2x3pin UART OUTPUT SELECT header
  • added J18 1x2pin UART1 header
  • added 1.8V stabilizer
  • populated SPI Vcc pin
  • modified capacitors near MAX3232 SOIC
  • reduced OC buffers GPIO header (J11) from 12 to 9 pin
  • eliminated issue with J6 USB port (unreliable detection of USB devices)


  • added RoHS logo
  • added Crossed Wheelie Bin logo
  • modified footprints of the pin headers


  • enlarged added holes


  • modified I2C GPIO expander outputs connections (now 4 of them are connected to the dedicated header)
  • modified version number on board
  • removed SPI header for APU recovery with output pin role information labels
  • removed 7 and 8 pin of SPI header with GPIO expander connection


  • added micro USB connector for power supply
  • added 5 V power supply pins
  • added SPI connector for APU SPI recovery
  • added fiducials on the bottom layer
  • added pins information labels
  • modified relay control system elements placement
  • modified SPI connector for APU paths placement
  • modified project text descriptions
  • removed 2 pin GPIO expander connector


  • added 5 V power supply signal diode (red) + limiting current resistor
  • added 3.3 V power supply signal diode (orange) + limiting current resistor
  • relay NO/NC connection switched to the previous configuration
  • switched SPI1_MISOwith SPI1_MOSI output
  • mirrored RS232 socket pads
  • removed I2C pull-up resistors


  • relay NO/NC connection switched


  • enlarged the hole diameter by 0.1 mm


  • added 3mdeb logo and board name on PCB
  • modified elements marks placing


  • added SPI output IO pins connection with GPIO
  • added PCB mechanical schematic
  • added I2C INT pins connection
  • added mounting holes
  • added fiducials
  • modified MOSFET transistor pinout numeration
  • modified USB footprint from horizontal to vertical
  • modified I2C GPIO expander with OC buffers connection


  • added mounting holes
  • modified relay pinout
  • removed I2C to GND connection


  • modified power supply from 5V to 3V3 for I2C bus MCP23017, and MAX3232
  • removed capacitors connected to the I2C bus


  • added I2C bus with output header
  • added MCP23017 I2C GPIO expander
  • added second SN74LS06 OC buffer
  • added relay with required neighboring items
  • added MAX3232 RS232 electrical level changer
  • added RS232 socket
  • added GPIO output header for pins unused to OC buffer control
  • modified some of input pins connection
  • removed ARK joint for the relay module
  • removed header for relay module control