Chapter 4: 29
4.4.5 Keyboard Interface Circuits
4.4.5.1 Keyboard Schematic (061-0166-XX)
The cathode of each LED is connected to ground. The anodes are connected to pins 9,
10 and 11 of J1.
The Reset key connects to ground and to pin 19 of J1.
The rest of the keys are wired into an x-y matrix with 5 columns KC0-KC4 and 5 rows
KR0-KR4. Pressing one of these keys connects one of the column lines to one of the
row lines. KR0-KR4 are connected to J1 pins 1, 2, 3, 4 and 5. KC0-KC4 are connected to
J1 pins 12, 13, 14, 15 and 16. KC4 is not being used yet.
4.4.5.2 Daughterboard schematic (061-0171-0x)
Page 1: J2 is the interface to the internal keyboard. The rows and columns from
the keyboard connect to the resistors surrounding J2. The resistors gener-
ate a different voltage from 0 to 3.3V for each key that is pressed. U15-A
buffers that voltage before feeding it to ADC0 on U1-A. The Reset key has
a separate line which arrives on J2 pin 19 and is then sent to U1-A pin 34.
The Power and Standby LEDs on the keyboard are driven by U1-A pins
31 and 32. The external keyboard signal from page 3 is buffered by U15-B
and then fed to ADC1 in U1-A.
Page 3: The external keyboard signal from the Connectorboard arrives at J5 pin 19.
4.4.5.3 Connectorboard schematic (061-x172-0x)
Page 3: The External keyboard signal arrives at J6 pin 3. It is then sent to the
Daughterboard via J5 pin 19.
4.4.5.4 Probeboard schematic (061-0177-0x)
Page 1: The External keyboard signal arrives at J6 pin 3. It is then buffered by
U15-A and fed to ADC1 on U1-A.
4.4.6 USB Circuits
4.4.6.1 Connectorboard schematic (061-x172-0x)
Page 4: The RS232 interface from the SBC arrives at J9. U18 and U19 convert the
signals from RS232 levels to TTL levels. U20 is the RS232 to USB UART.
The USB device port is sent to J7. U20 drives the USB Device port activity
LEDs on D1. The dual USB Host port signals arrive from the SBC on J10.
The Host signals are then filtered and sent out J8.
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