Midnight  GPS Display Terminal




Assembly & Test Guide

NOTE:  This product is a derivative of the Midnight SNA product.  The assembly process shown here still has references to the SNA and will be updated shortly to reflect the GDT nomenclature and parts.


Fig 1:  Overall Kit
Main GDT Kit consists of one bags (left) containing "PCB & Base Parts"


Fig 2:  Bag 1 Base Parts  (Refer to updated Parts List shown above-right.)
These parts form the base capabilities of the GDT.




Fig 4:  The Milled Enclosure Option



Fig 5:  Hardware provided in the Enclosure Option (milled and plain)



Fig 6:  Laminated Front Panel Overlay
(Label will be that of the GDT when this page is updated.)




Fig 7:  QVGA Display


Assembly Steps:

  1. Parts Inventory -- Make sure you have all parts shown in the various items picture above.  Note that you might not have purchased some of the options.

  2. PCB Preparation -- Using a fine-blade hack saw (or equiv), cut out the "X" areas in each corner of the pcb to allow it to fit into the enclosure.  Be careful to cut "on the inside" of the lines for the corner between J7and J2 so you  don't accidently cut the nearby trace on the bottom-side.

  3. Attach Connectors -- J1 (power), J5 (keyboard), J6 (serial), J12 (2x20 display connector), and J8 (28-pin IC socket for U1).  Note that J5 may have a metal shell, which fits into available holes.

  4. Attach Power On/Off Switch -- S1 must be mounted straight (perpendicular to board edge and flat against it. 

  5. Attach the 5V and 3.3V "voltage regulator" components (caps too) -- 5V VR1 ("462NL53B"), 3.3V VR2 ("ZLDO17-33"), C8, C9, C10, C11, C12 and C13.  Note that the "negative" side of the electrolytic tin can are indicated with a black stripe.  Be sure you have the orientation/polarity correct, and especially for C13, which is oriented differently from the others. [NOTE:  We previously indicated that the large tab on the VR2 package shouldn't be soldered down to the pad ... It's really okay to do this, and you should for best heatsinking!]

  6. Test Board Voltages -- Apply power to the 2.1mm coaxial power connector J1 and press the S1 switch "in" to turn the board on.  Measure 12V, 5V and 3.3V at the respective marked test point (pads) near each regulator.  Do not proceed until you ensure that you have the specified voltages on the test pads.

  7. Attach Q2 and VR4 -- These little SOT-23 packages look alike.  The package ID for Q2 is "1P", and the package ID for VR4 is "RKA".

  8. Attach U2, U3 and U4 Integrated Circuits -- Carefully noting the pin 1 location for each IC, insert and solder U2 and U3 (larger 20-pin DIP ICs), U4 (AD8307, the 8-pin SOIC). NOTE:  The "U4" location is actually labeled "U7" on the pc board.  (Oops!)  Also, DO NOT yet insert U1 (the pre-programmed 28-pin dsPIC controller) into its socket.

  9. Attach Q1 "2N7000" -- This TO92 package with its 3 leads on a "cardboard strip" is a MOSFET transistor.  Be sure to handle with anti-static care, form the leads to fit into the offset pad locations, oriented with the flat side of the transistor as indicated on the silkscreen.

  10. Attach All Remaining Parts -- Be careful to note polarity/orientation of the small SMT parts.

    • Note 1: The polarity of the speaker SPKR in upper-left corner of the pcb.  (+ sign in indicated on bottom of part.) 

    • Note 2: The 10uF SMT capacitor C23 located near U4 is non-polarized, so it doesn't matter which way you attach it.

    • Note 3: C5 is supplied as a surface mount device (SMD) chip capacitor, yet the board layout/silkscreen is for a larger electrolytic capacitor. (Oops.)  The SMD cap is correct, so solder either end to one of the pads, and use a short wire to connect the other end of the cap to the other pad.)

  11. Attach Programming Connector ICD1 -- Mount this 2x3 pinheader on the bottom side of the pcb.

  12. Attach 4 PCB Mounting Standoffs -- Using the parts from the Enclosure Hardware bag, attach the four aluminum standoffs on the bottom side of the pcb, using the short 2x56 (smaller thread) screws.

  13. Attach 2 Display Mounting Standoffs -- Using the two, shorter 4-40 threaded aluminum standoffs to the top of the pcb next to J2 and J3 BNCs.

  14. Attach U6 to Bottom of QVGA Display -- Noting orientation of pin 1 on U6 (256 Kbit EEPROM), attach to the IC1 position on the bottom of the QVGA Display.


Power Up & Test  (v4.xx)

1.   Check DC Levels ... Before installing the dsPIC microcontroller and display module, make one final check of the DC power levels.

2.   Install U1 and Display ... Install the pre-programmed dsPIC processor U1 and the QVGA display module, making sure the display connector is properly lined up with the connector on the PCBA.  Do not install the MSNA assembly in its enclosure until completing all the steps in this guide.  You will need access to components on the back of the main PCBA for calibration.

3.   Power On! ... Leave the SD card out, the keyboard unplugged, and then turn power on.

4.   Splash Screen is Displayed ... After a pause of up to five seconds, you should see the splash screen showing the firmware revision level.  (If you hold your finger on the screen while the splash screen is displayed, the splash screen will be displayed until you raise your finger.)

5.   Beep Beep ... The splash screen will be displayed for about 3 seconds and then the Terminal mode screen will be displayed (top line for keyboard input, blue area for output received from the serial interface).  You may also hear "GO" BEEPed in Morse code ("--. ---").

6.   So Far So Good ... If you got this far, there’s a good chance that everything is working.

7.   Plug in Keyboard ... Turn power off, plug in the keyboard, and turn power on again.

8.   Keyboard LEDs Flash ... You should observe the same power up sequence as before except this time you will see the LEDs on the keyboard flash twice, the first time when power if first turned on and the second time when the splash screen is finished and the MSNA resets and initializes the keyboard.  You should also hear a BEEP at the time of the second LED flash.

9.   Type and See Text ... At this point, characters typed on the keyboard should appear on the input line.  Pressing Enter on the keyboard will send the text out the serial interface (3.5m stereo jack) and clear the input line.  Pressing and releasing the Insert key will toggle the INS/OVR indicator in the upper right corner of the display.  Pressing Home will clear any text on the input line.

10. Make Loop-Back Connector .. Make a loop-back connector for the serial port that connects RxD to TxD and connect it to the serial port.  Now when you press Enter on the keyboard, any text on the input line will be sent out the TxD line and received back on the RxD line and displayed in the blue output area of the display.  Pressing Alt-Home will clear any text in the output area.

11. Scroll Lock is Important ... Press and release the Scroll Lock key on the keyboard and observe the Scroll Lock LED turning on.  This indicates successful two-way communication with the keyboard.  (The Caps Lock and the Num Lock keys and the associated LEDs should also be working.)

12.  See Command Mode Menu ... When the Scroll Lock LED first comes on, the Command mode menu will be displayed.

13.  Three main screens:
1) Clock Display
2) GPS Satellite Display Screen
3) Terminal Data Entry

17.  Set Baud Rate ... Select Command mode (press and release Scroll Lock) again and Select B (Serial Interface bps) to display the BAUD RATE menu.  Select 7 (38400 bps, the default) and press Enter to save your selection to EEPROM.

18.  Mounting the PCB Assembly (PCBA) in the Enclosure ... Now that everything is working, you can mount the MSNA in its enclosure by carefully angling the PCBA into the milled enclosure.  It may help to push in the S1 power switch so it doesn't stick out quite as much, thus giving you a little more room. Use the four remaining 2-56 screws (7/16") to attach the PCBA through the four holes on the bottom side of the enclosure.  Some "compliance" was designed into the mounting arrangement to allow you to slightly adjust the position of the PCBA.  Start by loosening the four pcb mounting screws on the top of the board, then loosely screw in the four longer screws on the bottom of the enclosure.  Align the PCB so all connectors and switches protruding from the sides of the enclosure are centered within their cutout areas, then carefully tighten down the eight screws that hold everything together.

26.  Attaching the Front Panel Overlay ... Apply strips of double-sticky tape around the backside perimeter of the laminated Overlay.  (Scotch brand "Scrapbooking Tape" p/n 34-8700-9324-1 is perfect, but any double-sided tape, rubber cement or glue works well too.)  With the enclosure lid screwed in place, carefully place the Overlay on the front panel, ensuring that the four holes in the corners are aligned over the four black screws that mount the lid to the enclosure body.  Firmly press down on the Overlay (where the tape/glue is beneath) to ensure a sufficient adherence to the plastic lid.

27.  Calibrating the Touch Screen ... Once you have mounted the MSNA in its enclosure and verified everything is still working, let's calibrate the touch screen.

a.   The calibration function is started by touching the touch screen when power is first turned on. 

b.   When you see "TAP EACH CROSS" displayed, stop touching the screen and the first cross will be displayed.

c.   Touch the center of the cross with a stylus.  This is best done by touching the screen and dragging the stylus to the center of the cross and then raise the stylus.  The MSNA records the last point touched before raising the stylus.

d.   After the each cross has been touched, another cross will be displayed.  Touch each in sequence until all nine crosses have been displayed and touched.

e.   After the last cross have been touched, the display will change to a simple Etch-A-Sketch screen with two buttons at the bottom.  Use your stylus to draw on the screen and see how close the drawn line follows the point of your stylus.

f.    If  you are satisfied with the touch screen calibration, touch the EXIT button and the MSNA will save the calibration data in EEPROM and start normal operation.

g.   If  you are not satisfied with the touch screen calibration, touch the REDO button and the touch screen calibration sequence will restart.

28.  Using the GDT with an external GPS receiver via the serial data stream


Congratulations!!! You now have a working Midnight GPS Display Terminal.
So so now get out the GDT Quick Reference Guide and get to work!




(Image will be that of the GDT when this page is updated.)



Copyright 2020 Midnight Design Solutions, LLC.  All Rights Reserved.
Page last updated:  Aug 1, 2020