Wiki VMAC PiHat Service Note 1

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VMAC PiHat v1
VMAC PiHat v2

Service Note 171231 for VDAS PiHat v1.1 | December 2017

Default HAMKit VMAC PiHat v1 configuration

• 3 x Video inputs on AV1, AV2 and AV3 (75 Ohm)
• 3 x Audio inputs on AV4, AV5 and AV6 (600 Ohm)

• 2 x Video outputs on A/V 1 and A/V 2 (75 Ohm)
• 2 x Audio outputs on A/V 3 and A/V 4 (600 Ohm)

The default matrix use may be altered for personal preferences simply by updating the input and output resistors and capacitors as shown in the Wiki VMAC PiHat Schematic and also Wiki VMAC PiHat Matrix

The default set address for the FMS6501A is 86h (DEVICE_ADDR = 0x43).


The two Pi audio loop backs to HAMKit VMAC PiHat inputs AV_IN5 and AV_IN6 are enabled (links soldered). This means AV_IN5 and AV_IN6 (RCA), are paralleled to the Pi 3.5mm Socket.  The Pi Video goes direct to a separate VIDEO_PI input on the Matrix.

5V Supply

The 5V link is set/soldered, so DC power in via the 2.1mm DC socket, will flow to the Pi 5V on the header.  This can be safely left set, if alternatively using the PI 5V power input.

If you are not planning to use the DC input > 5v, then we would recommend just using the normal Raspberry PI 5V micro USB power, as this is more than adequate to power a single HAMKit VMAC PiHat

Regulator Heatsink

If using the DC input on the HAMKit VMAC PiHat, the LDO regulator will get very hot. We recommend a heatsink on the regulator, especially if using for long periods. A small heatsink is provided in the kit but you may need to fit a larger one, depending on the use.

Long Pin Header and Spacers

As the HAMKit VMAC PiHat can be used on a number of different Pi hosts (v2, v3, Zero etc.), or could be slave stacked, the header connector is not soldered in place, in order to allow you to configure height as needed.  Some users have been known to alternatively use a short ribbon cable, or wires, to the Raspberry Pi to save height.

The 40 pin GPIO Header is connected to the HAMKit VMAC PiHat via two long pin 20 way headers, due to the stocking of long pin 20 way headers.

These 20 way headers will require filing very slightly on one end, where they meet in the middle.

The provided spacers are optionally are for fitting over the long pins. Should you wish to use them, they will require to be cut down to your required height.

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