| ECM (Electronic Counter Measures) panel
An other candidate for a local control |
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Introduction
The ECM panel has only a few different components. They are:
- two 3-position "flat-top" switches OPR/STBY/OFF and XMIT 1/2/3
- two push-buttons, a red colored RESET and a white colored BIT
- one rotary knob DIM
- eight Jay-El push-buttons, each with 4 separate lamps
- two Grimes lamps for panel illumination
A quick inventory of the required I/O leads to the following conclusions. The required connections to the switch matrix is 14
connections. The panel backlighting is straight-forward, no need to cut material at the rear side of the panel to implement LED
backlighting, because the Grimes lamps take care of this. In interesting note here is that the ECM panel
illumination is red, just like the other "top secret" panel in the pit, KY58. So far, nothing special.
However, the 8 Jay-El push-buttons each have 4 lamps that can be lit separately. That implies 32 wires for the lamps!
ECM panel interface ideas
After the initial inventory of required I/O connections, I started drawing the connection panel for the ECM
panel. Sticking to my ideas of separate connector for specific types of signals, I would need a 9-pin Sub-D for the backlighting,
another 9-pin Sub-D for the switch matrix, one round "CB" connector for the analog (potmeter) signal, and one 25-pin Sub-D plus a
9-pin Sub-D for the lamps. And in total that would be over 40 wires, and at least 4 separate cables!
Thinking of PHCC hardware, the ECM panel requires an analog input, 14 switch matrix connections, and 32
digital outputs. As the PHCC "40DO" daughterboard supports up to 40 digital outputs, and the ECM panel
already requires 32 of them, the idea was born that a "local 40DO daughterboard" would make sense, because that would eliminate
the 32 wires for the Jay-El lamps through the pit. But after reading some ECM panel info on the F-16 "bible website"
F16-C Reference Library (Original > Parts > Left console > ECM),
I found a few more good reasons to implement a local PHCC daughterboard for the ECM panel.
- The white BIT button has just one single function. "BIT" stands for "Built-In Test".
When you push this button all 32 lamps in the 8 Jay-El are illuminated at maximum brightness.
- The DIM rotary knob is a potmeter that controls the brightness of the lamps in the Jay-El push-buttons.
Using the standard PHCC control modules, the DIM potmeter would be connected to a simple NE555-based PWM
generator driving the lamps via a MOSFET. But ... that MOSFET would have to be in the supply connection of the 32 digital outputs
of a standard 40DO daughterboard. In fact, the 32 (long) wires in the pit to these lamps are 32 PWM pulsing wires! To prevent
EMC (not ECM) issues, it would be wise to use a shielded cable for these 32 lamps.
Further, some software on the PC must detect the BIT button, and when the button is pressed must turn on
all lamps at maximum brightness, regardless of the DIM knob setting. Thus, the NE555-based PWM generator must have a connection
to switch the PWM duty-cycle to 100%.
The Jay-El push-buttons with 4 separate connected lamps were found on a panel taken from a British Nimrod aircraft. It pays off
to keep a watch on eBay. These pictures give you an impression of the wires only for those 8 Jay-El push-buttons and their
32 lamps ...
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| The text legends on the Jay-Els still need to be modified. |
A "few" wires, lamps and one switch contact. |
Thinking of all the requirements to control the ECM panel made me realize that this panel is a perfect
candidate for its own "local" PHCC daughterboard. To summarize the "ECM PHCC daughterboard" functionality:
- control of 32 lamps independently
- potmeter connection to control lamp brightness
- push-button to test all lamps at maximum brightness
I listed the "features", because these are exactly the same as required for a PHCC daughterboard" to control the CAUTION panel!
The CAUTION Panel also has 32 lamps for a start (and thus so many wires to connect). The other functionality "hidden" in the
CAUTION panel is how the 32 annunciators can be lit. They light up at maximum brightness, or with the appropriate pin wired at
a fixed dimmed intensity. The dimmed state is (as far as I know) controlled by the MAL & IND LTS BRT/DIM
switch and functionality on the (INTERIOR) LIGHTING panel. To use the ECM daughterboard to control the CAUTION panel, you simply
connect a trim potmeter (instead of the DIM potmeter) and use the BIT push-button input as the control signal to set the
annunciators to the dimmed state.
ECM PHCC daughterboard design
Just like all other PHCC daughterboard, the ECM PHCC daughterboard is based on the 18F252 PIC processor. For the digital outputs
I used a different approach. The 40DO daughterboard uses five 8-bit shift registers to create 40 outputs, but as this design has
sufficient I/O pins, I used four 8-bit latches to create the 32 outputs for the lamps. As each lamp needs more current than the
octal latch output can supply, the ULN2803A buffer is used. Also, without the buffer the lamps would have to be 5 Volt types.
Using the buffer allows you to use 28 Volt (original) bulbs. By selecting the 74LS573 octal latch, the board design is
much simplified, because the 74LS573 has all D inputs at one side of the DIL package and all Q outputs at the other side.
One input (A0) is configured as an analog input and connects to the DIM potmeter. The C2 pin is configured
as PWM output and drives a MOSFET output stage to control the brightness of the 32 lamps. One digital input connects to the
BIT push-button, software debounces the contact. 8 outputs are connected to the D inputs all all four octal
latches. The LatchEnable pin of each latch is connected to a separate output pin of the PIC.
As there are five I/O pins not used, I connected an LED to one output. It serves as a "diagnostic indicator".
Click the image to view a full-sized schematic drawing.
The design has 4 I/O pins not used. You could use one of them as a jumper connection to signal the usage: ECM or CAUTION panel.
This is needed, because the function of the "BIT" input is maximum brightness for ECM and dimmed brightness
for CAUTION. Of course, you can forget the jumper and just apply the correct logic level to the input pin ...
Prototype of the ECM PHCC daughterboard
As there is some space left at the left side, I was able to add connectors for the switches and push-button on the
ECM panel and the 8 push-button contacts of the Jay-Els, including the diodes required for anti-ghosting
in the switch matrix. One 2x5 pin header is all that is needed to connect all switch contacts of the ECM
panel into the switch matrix.
ECM PHCC firmware
The ECM PHCC daughterboard connects to the DOA communication channel, just like all other PHCC daughterboards. I selected hex 45
as the device address (hex 45 is ASCII "E" for ECM). With the "sub-address" the specific functionality from the ECM panel is
selected. The sub-address can be 0 up to 5 (inclusive).
| sub-address | data byte |
Description of functionality |
|---|
| 0 | 8 bits |
each bit corresponds to one lamp of the top "row" 2 Jay-El push-buttons at the left side.
"0" :: lamp off / "1" :: lamp on. |
| 1 | 8 bits |
each bit corresponds to one lamp of the top "row" 2 Jay-El push-buttons at the right side.
"0" :: lamp off / "1" :: lamp on. |
| 2 | 8 bits |
each bit corresponds to one lamp of the bottom "row" 2 Jay-El push-buttons at the left side.
"0" :: lamp off / "1" :: lamp on. |
| 3 | 8 bits |
each bit corresponds to one lamp of the bottom "row" 2 Jay-El push-buttons at the right side.
"0" :: lamp off / "1" :: lamp on. |
| 4 | 8 bits |
each bit corresponds to one lamp of the top "row" 2 Jay-El push-buttons at the left side.
"0" :: don't care / "1" :: lamp on. |
| 5 | 8 bits |
each bit corresponds to one lamp of the top "row" 2 Jay-El push-buttons at the right side.
"0" :: don't care / "1" :: lamp on. |
| 6 | 8 bits |
each bit corresponds to one lamp of the bottom "row" 2 Jay-El push-buttons at the left side.
"0" :: don't care / "1" :: lamp on. |
| 7 | 8 bits |
each bit corresponds to one lamp of the bottom "row" 2 Jay-El push-buttons at the right side.
"0" :: don't care / "1" :: lamp on. |
| 8 | 8 bits |
each bit corresponds to one lamp of the top "row" 2 Jay-El push-buttons at the left side.
"0" :: don't care / "1" :: lamp off. |
| 9 | 8 bits |
each bit corresponds to one lamp of the top "row" 2 Jay-El push-buttons at the right side.
"0" :: don't care / "1" :: lamp off. |
| 10 | 8 bits |
each bit corresponds to one lamp of the bottom "row" 2 Jay-El push-buttons at the left side.
"0" :: don't care / "1" :: lamp off. |
| 11 | 8 bits |
each bit corresponds to one lamp of the bottom "row" 2 Jay-El push-buttons at the right side.
"0" :: don't care / "1" :: lamp off. |
| 12 | DIAG mode |
controls the operation mode of the DIAGnostic LED on the ECM Control board.
data byte = 0 :: the LED is always OFF
data byte = 1 :: the LED changes state every PHCC ECM command is received
(sort of visual "ACK").
data byte = 2 :: (or any value not 0 or 1) the LED blinks with a 1 Hz "heart beat" (default at power-up). |
| 13 | 4 bits |
controls the 4 spare digital outputs X0 thru X3
data byte bit 0 (0x01) :: X0 pin
data byte bit 1 (0x02) :: X1 pin
data byte bit 2 (0x04) :: X2 pin
data byte bit 3 (0x08) :: X3 pin
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To have an indication that the ECM panel control starts, the lamps in the Jay-Els are lit "row" by "row" at power-up at the
brightness set by the DIM potmeter. That is a frivolity I have put in my design, I am pretty sure
this start-up behavior is not seen in the real F-16. By design, when you press the BIT button all
lamps are lit at maximum brightness as long as the BIT button is pressed.
Construction of the ECM panel
Basically, the ECM panel is a "sandwich" of 3 parts.
- The ECM panel from Mike with the backplate
- the circuit board with the ECM PHCC daughterboard logic
- the connector bracket
Due to the local PHCC controller, the number of connectors at the rear side is low. In my interconnection scheme of all
switches of the left side console, some matrix signals are passed on to a neighboring panel, thus there are two 9-pin Sub-D
connectors for the switch connections. Another 9-pin Sub-D connector is for the (Grimes) panel backlighting and
the +28 Volt power supply for the Jay-El lamps. Finally, a 8-pin round "CB" connector is used for the DOA communication channel.
