Power Supplies; Communications; Audio Data - Covidien ForceTriad Service Manual

Footswitch/Audio PCBA Circuitry Description

Power Supplies

This PCBA requires 2 power supplies: 5 V and 12 V. From those input voltages it also
generates 2.5 V, 3.3 V, and isolated supplies of +12 V, -12 V and +5 V. 5 V and 12 V are
delivered to this PCBA through the RF PCBA connector.
The 2.5 V and 3.3 V supplies are regulated down from the 5 V supply on this PCBA. The
5 V rail should draw approximately 100 mA. The 12 V rail should draw approximately
500 mA at full volume with no expansion port peripherals connected.
The 12 V supply is used by the audio amplifier, TPA1517, and also generates all of the
isolated-power supplies. The isolated-power supply can source approximately 250 mA on
each, +12 V ISO and -12 V ISO, and 500 mA on +5 V ISO.

Communications

All communications between the controller PCBA and the Footswitch/Audio PCBA are
conducted over a two-wire System Management Bus (SMBus). The master of this bus is
the controller PCBA.

Audio Data

Three commands can be received from the controller PCBA; reset, parameter write and
parameter read. The reset command resets all internal-state machines inside the FPGA. It
also immediately stops a running audio stream. The parameter commands allow the
controller to write and read three internal parameters that control sending out audio
data.
These parameters are: wave file, duration, and volume.
The wave-file parameter selects a particular wave file in the flash memory by selecting a
base memory address from a look up table.
The duration parameter selects how many times to repeat the wave file. Since each wave
file is a fixed length, that file can be repeated up to 30 times, or it can be told to be sent
out continuously until another command is received.
Finally, the volume parameter simply selects a volume level between 0 (mute) and 1024
(highest volume, approximately 60 dBA).
When a command is received, the FPGA processes that command only once. For
example, if a particular wave file is selected to be played twice, the FPGA plays that wave
file twice and then stop until a new command is received. If a wave file is to be played
continuously, it can be set using the duration parameter.
ForceTriad Energy Platform Service Manual 3-11