This PCB handles the VFD, keyboard scan, IR reception for the front panel &
power LEDs.
The micro is an Atmel AT91SAM7S32 (IC101) which must be initially
programmed via the Atmel/Segger debugger via CON101. Subsequently, the
micro can be reprogrammed from the PW338 using the Arcam upgrader utility
over RS232. The bootloader should never need to be updated and as such
will not be included in the standard upgrading application.
Communication with the PW338 is via RS232 – IC101 sends information on
keypresses to the PW338 & receives information to display & brightness
commands from the PW338 – FP_TX & FP_RX. Note these signals are
labelled with respect to the PW338.
IC101 uses +3V3_PW338 so is powered in standby. It has an internal 1V8
regulator which generates VDD_OUT (1V8, pin 8) which is decoupled &
powers the core & PLL of IC101 (pins 18, 41 & 48).
The VFD (DISP100) is driven from serial data SIN from IC101
(AT91SAM7S32 micro). The serial data is gated through IC102 (74HC08
quad NAND gate, parts C & D unused) controlled by SIN1_CTL & SIN2_CTL
from IC101 to provide dimming of the display. The output data from IC102 is
clocked into the display with the signal CLK from IC101 and is latched into the
display during the blanking period (LAT & BLK).
The VFD filament drive is synchronous with the display update. Signals
FClock1 & FClock2 are 180deg out of phase and drive IC100 (AD8532 op
amp) to give a 6V oscillating drive to the two ends of the filament (from +6V_1
– L123). The HT is provided direct from L123 (+40V_VFD). +6V_1 &
+40V_VFD are not present in standby.
IR decoding (RX100) is powered by +5V_STBY, allowing IR reception when in
standby. The signal pass through L121 (Connection) to L118 (Trigger) before
going to L122 (Main PCB).
The power LEDs are fitted to a small snap-off PCB that is connected via a 3
wire lead. Green LED when the unit is on, Red when in standby, both during
power on.
L126AY – Front Panel