VMAC PiHat v2 Specification

The HAMKit VMAC AV PiHat v2, is a small board which provides a very flexible Audio and Video Switching Matrix, with on-board DTMF Decoder, OSD graphics, Video Signal Detectors and EEPROM.  It is available in two versions.

This new board was designed principally as a Raspberry Pi add-on board, however, it can also be connected to other I2C enabled devices such as Arduino, Microchip, Tablets or PC.

The HAMKit VMAC AV PiHat v2 board (versions), is an update to the original Wiki VMAC PiHat Specification

  • Full size quality two layer Raspberry Pi Hat board to HAT mechanical specification
  • Size 85mm x 56mm
  • Weight: PCB with connectors 40g, PCB without connectors 20g
  • Standard 40 pin Pi GPIO header
  • All logic I/O (GPIO), levels are at 3v3
  • Impedance Video 75 Ohms and Audio 600 Ohms (Line Level)
  • Programmable individual Video input Clamp, Bias and Gain
  • 9 x AV Inputs to Matrix
    • 6 x RCA Sockets – Component configurable for Video or Audio Inputs
    • 3.5mm Jack Socket providing (Used to loopback from Pi 3.5mm Socket)
      • 1 x video Input
      • 2 x audio Inputs
  • 4 x AV Outputs from Matrix
    • 4 x RCA Sockets – Component configurable for Video or Audio Outputs
  • Pi Zero video connector Pin Header
  • 4 x matrix logic control inputs
    • Connected to GPIO on Pi GPIO header
  • FET switched output (Intended for PTT)
    • Connected via GPIO on Pi GPIO header
  • PiHat powered from on-board 3V3 regulator
    • Taking 5V from Pi Header
  • DTMF decoder (CM88L80)
    • Logic outputs to GPIO on Pi GPIO header
    • Level control preset on PCB
  • OSD (MAX7456)
    • Controlled from SPI on Pi GPIO header
  • 3 x Video Signal Detectors (MAX7461)
    • Connected to AV Inputs 1, 2 and 3
    • Logic outputs to GPIO on Pi GPIO header
  • 4 x On-board LEDs.  3v3 Power, User, Status and PTT
    • Optionally connected to either E2 ID, or I2C, on Pi GPIO header
    • Connected to GPIO on Pi GPIO header
    • RTS is also connected to a LED, allowing multiple use
  • Two PiHat boards may be stacked for increased A/V IO count
    • Require to unpopulate DTMF on 2nd board
    • Require to clear EEPROM solder jumper on 2nd board
    • Change matrix I2C address via solder jumper on 2nd board
  • Eleven test points on PCB for expansion, testing or other uses
  • Mounting holes
    • Suitable for Raspberry PI 2, 3 or Zero risers
  • Component Temperature Range 0°C to 85°C
  • Operating Temperature  Range 0°C to 45°C
    • Air movement over PCB is advisable at high temperatures

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