The Mega Frame Page

Jan/Feb 2023

The idea for this new project is to have a picture frame with, not 1, but 9, 2.8" LCD SPI displays; hence the name Mega Frame. The frame displays various categories of images that I have photographed, computer generated or collected over the years along with some misc computer graphics. It is motion activated in that the back lights for all of the LCD displays turns on when motion is detected to show the images and then turn off again after 3 minutes. The frame changes image categories every 6 minutes. The Mega Frame is powered by a Raspberry Pi Zero W because I happen to have one, but any Raspberry Pi would probably work. I like the Pi Zero W because it has WiFi capabilities so I can develop the software remotely via SSH. I can even change the software while the Mega Frame is hanging on a wall in my house. I wrote all of the frame's software from the ground up in GForth because I like programming in Forth and I have found GForth really capable. Besides designing the hardware and software I built a box for the frame out of wood which I stained and waxed. The pictures below document the frame's build process.

Picture	Description
	Here is the breadboard I used to verify my design for the Mega Frame. On the left is the white PIR motion detector and two LCD displays. On the bottom right is the Raspberry Pi Zero W which is powering the frame. The motion sensor is really sensitive so it will pick up any kind of motion over a great distance. Even across a room is some cases. The displays were bought at Aliexpress.com for $4.24 each which I thought was quite the deal. I ordered 13 when I only needed 9 to be sure but all 13 seemed, at first anyway, to work perfectly. These displays do not have touch support, that cost a little extra.
	I made a frame like box to hold the 9 LCD displays. It is made of pine molding for the sides and 1/8" veneered plywood for the front and back. The front plywood piece was cut out using my Ortur laser cutter. After all of the machining, I glued the front to the box and used a flush cut router bit to trim the front to the sides. After that, I stained the whole thing with dark walnut stain. Finally, I coated all surfaces with wax.
	While the front of the frame/box is glued on, the back is held on with screws for easy assembly and future maintenance. I will add a frame zig zag mount so I can hang the finished Mega Frame on the wall.
	With the back off I mounted the 9 LCD displays to the frame using hot glue. You can see the power connector and wires at the bottom of the frame. The frame will be powered externally by a 5 VDC wall wart. The SD card interface on each display module was not used in this project. All image files are stored on the SD card in the Raspberry Pi.
	Front view of Mega Frame with all displays mounted. The white circle is the PIR motion sensor. The frame is starting to look real. It shouldn't be long now before I can see the first images.
	The rats nest evolves. I used push on jumper wires for connection to the Raspberry Pi so I could remove it in the future if another project required it. Hopefully the Raspberry Pi shortage will be resolved in 2023 and I won't have to worry about wasting a Raspberry Pi Zero W in the future.
	Done with all of the wiring. Unfortunately the frame doesn't seem to work for some reason. Tomorrow I will trouble shoot and find out why. I found a minor wiring error and now the frame works as expected. Time to button up the frame and call the hardware done.
	With the frame's hardware checked out I screwed the back on and will now concentrate on the frame's GForth software.
	I battled instability in the Mega Frame for weeks. I found a couple of software issues and a couple of bad solder joints but fixing them made things better but the frame would still not run for more than a day without issues. I thought the instability was probably the result of one of two issues: inadequate power supply and/or possibly heat buildup within the frame. So I first changed the 5 volt power supply from a 1 amp to a 2.5 amp supply but that did not fix the instability. So, in desperation, I took the back off the frame and drilled a series of holes to allow for better air circulation. At that time I put a couple of felt pads on the lower part of the back to prevent damage to the wall it hangs on and to allow better air flow. With the holes drilled in the back the frame ran for 3 1/2 days before the displays started malfunctioning so heat buildup might be the issue. This theory is further advanced because after the malfunction I can unplug the frame and plug it back in and it still won't work correctly. But if I leave it off for some length of time (~ 1 hour) I can plug it back in and it will run fine. So with that in mind, I drilled 3 holes in the top of the frame and 2 holes on each side and the bottom to further air circulation. I think I have finally found the actual problem with the Mega Frame and it is not heat. When I wired the SPI bus connections I didn't do it like a serial bus structure. Instead I wired the RPi Zero to the middle display and then had the signals fan out from there. This resulted in multiple paths for the high frequency signals that they did not like.  Since I  rewired the frame as a single continuous bus, the frame hasn't malfunctioned. I have my fingers crossed that the wiring topology was the actual problem.

Electrical Connections
Connections between the Raspberry Pi Zero W and the other hardware which includes the 9 displays and the PIR motion sensor.
Displays are numbered left to right and top to bottom.

Signal Name

Pi Zero Pin

Pi Zero GPIO

Display 0

Display 1

Display 2

Display 3

Display 4

Display 5

Display 6

Display 7

Display 8

PIR

+5 VDC

2

n.a.

VCC

VCC

VCC

VCC

VCC

VCC

VCC

VCC

VCC

GND

6

n.a.

GND

GND

GND

GND

GND

GND

GND

GND

GND

-

CS0

3

2

CS

CS1

5

3

CS

CS2

7

4

CS

CS3

11

17

CS

CS4

13

27

CS

CS5

15

22

CS

CS6

8

14

CS

CS7

10

15

CS

CS8

12

18

CS

RESET

29

5

RST

RST

RST

RST

RST

RST

RST

RST

RST

D/C

31

6

D/C

D/C

D/C

D/C

D/C

D/C

D/C

D/C

D/C

MOSI

19

10

MOSI

MOSI

MOSI

MOSI

MOSI

MOSI

MOSI

MOSI

MOSI

SCLK

23

11

SCK

SCK

SCK

SCK

SCK

SCK

SCK

SCK

SCK

BL *

33

13

LED

LED

LED

LED

LED

LED

LED

LED

LED

+3.3 VDC

1

n.a.

+

PIR OUT

16

23

OUT

As you can see the signals +5 VDC, GND, RESET, D/C, MOSI, SCLK and BL are wired to each display in parallel.
Only the chip select pins are unique to each display.
The Raspberry Pi SPI interface is configured to run at 20 MHz.
The external 5V 1 amp power source (wall wort) is connected to +5 VDC and GND.
* I had to put a 2.2K ohm resistor in the BL (back light) signal line as I think the direct connection was causing a problem for the Raspberry Pi that resulted in corrupted images.

Mega Frame Software
All of the software for the Mega Frame is written in GForth which I have found very nice. The software is made up of many GForth files.
To understand how the code works requires a working knowledge of Forth and specifically GForth.
The files and a short description of their content is given below.

GForth Filename	Function
bitfield.fs	64 bit bit field functions used to guarantee uniqueness in random numbers and random selections.
bmpReader.fs	Code used to read 320x240 32 bit BMP image files from the filesystem
colorfunctions16.fs	Only the wheel function is used from this file to create 16 bit colors for display
font5x7.fs	Font used to draw text on the screens
frame.fs	Main code for the Mega Frame. The "main" word is the entry point for code execution
imageManager.fs	Code for managing the directories of image files
load	A GForth include file for loading all of the Mega Frame software
loadrun	GForth include file for loading and executing the Mega Frame software
mdGraphics.fs	Functions for drawing circles and lines on the virtual multi display screen
mdILI9341.fs	A display driver for ILI9341 display devices extended for controlling 9 displays
misc.fs	Various array definitions and other things required for the frame's operation.
random.fs	GForth C interface to Linux random functions
text.fs	Code for drawing text strings on the displays
wiringPi.fs	A library of functions for controlling the Raspberry Pi's GPIO pins and the SPI interface(s).

In addition to the GForth code there are numerous directories of images as described below.
Image must be in 320x240 32 bit BMP format.
Images in these directories must be named iN.bmp where N is 0 up to number of images in the directory minus 1.
Ex: i0.bmp, i1.bmp, etc.
There is a limit of 64 images per directory named i0.bmp .. i63.bmp. This has to do with limitations of the bitfield.fs code.

Directory Path	Content
images/abstract	A collection of abstract images most of which I have generated over time.
images/amazing	A collection of amazing images I have collected from the Internet.
images/fractals	A collection of fractal images I have created and/or found on the Internet.
images/garden	A collection of images of the Garden of the Gods Park in Colorado Springs. One of the most beautiful parks in the world as far as I am concerned. These are a combination of pictures my wife and I have taken plus many from the Internet.
images/psychedelic	A collection of psychedelic and surreal images I have collected over the years.
images/raytraced	A collection of ray traced images most of which I created but there are a many I gathered from elsewhere.
images/space	Being a Space fan I have gathered quite a collection of space images some of which are provided here.
images/volcanoes	I am fascinated by Geology so I have collected quite a number of images of volcanoes and hot springs over the years.

The following are the basic step you would need to take to reproduce the Mega Frame:

1. Install the latest non GUI 32 bit version of the Raspberry Pi operating system on an SD card

2. Install GForth and wiringPi (with its required prerequisites)

3. Create a gforth directory off of your home directory

4. Unzip the provided Mega Frame software into the gforth directory. The software for the Mega Frame can be found here. You may want to check back periodically as I am constantly changing the software to fit my whims (;>)

5. To test the install change to the gforth directory and execute: gforth-fast loadrun and see what happens.

6. If all is well, read the service.txt file in the resource/service directory about how to make the Mega Frame code run as a Linux service that will restart every time the frame is powered up.

Note: If you plan to use more and/or different images you must understand the operation of the imageManager.fs code in detail.

************* Good luck building your own Mega Frame *************