Technical Supplement
S- 8
S4.2.1.4 Speaker Driver and Volume Control
As illustrated in Figure S4-3, speaker tones originate from the U3 GPT
output compare-pin (OC2). The GPT pin outputs a square wave whose
frequency is under software control. This signal is buffered by U6, then input
into DAC U5. The DAC may be programmed to attenuate the signal to one of
256 levels, effectively acting as a volume control. This signal is then sent to
speaker driver U22 that drives an 8–32
Ω
speaker.
HC16
GPT
Buffer
DAC
Volume
Control
Driver
Speaker
Square wave
of known
frequency
Attenuated
square
wave
Audio driver enable signal
Figure S4-3: Speaker Driver and Volume Control Block Diagram
S4.2.1.5 Connectors
This section describes UIF connectors and provides tables that detail
connector pin-outs.
J1 — is a 20-pin connector that interfaces the UIF/Power Supply PCB to the
Blood Pressure module. A ribbon cable is attached from J1 to the Blood
Pressure module.
Table S4-1: J1 Connector
Pin No.
Pin Description
Input/Output/
Power
1
Transmit data to Blood Pressure module (TXD)
Output
2
Receive data from Blood Pressure module (RXD)
Input
3
Request to send (XRTS)
Output
4
Status from Blood Pressure module (OK = LOW)
Power
5
Logic ground
Input
6
VDD
Power
7
Blood Pressure module power (positive)
Power
8
Blood Pressure module power (positive)
Power
9
Module power ground
Power
10
Module power ground
Power
11
Blood Pressure module power (negative)
Power
12
Pump power
Power
13
Pump power
Power
14
Pump power
Power
15
Pump power ground
Power
16
Pump power ground
Power
17
Pump power ground
Power
18
Reserved
19
Spare
20
Reset signal to Blood Pressure module
Output
