You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
85 lines
4.2 KiB
Markdown
85 lines
4.2 KiB
Markdown
1 year ago
|
Adapter PCB to support up to 3 panel chains
|
||
|
|
===========================================
|
||
|
|
|
||
|
|
* Supports up to three panel chains for newer plus models and
|
||
|
|
Raspberry Pi 2 that have 40 GPIO pins.
|
||
|
|
* Uses HCT245 to level shift signals from 3.3V to 5V and shield
|
||
|
|
the Raspberry Pi GPIOs from overloading.
|
||
|
|
* Open source KiCAD PCB EDA format.
|
||
|
|
* Optional: Pads to power the Pi with 5V, including optional capacitor footprints.
|
||
|
|
* Connector for RxD input (literally the only GPIO pin left) in case you want to
|
||
|
|
make your panel controlled with a serial interface (3.3V logic level).
|
||
|
|
* Provides a way to choose the pinout for different kinds of 64x64 matrixes.
|
||
|
|
* (not very pretty layout, was just lazy and let the auto-router generate the first pass)
|
||
|
|
* BOM:
|
||
|
|
- 4x 74HCT245 or 74AHCT245 in 20-SOIC, 7.5mm package which should make
|
||
|
|
it easy to hand-solder. Make sure to get the variant with the **T**: HC**T** or AHC**T**
|
||
|
|
(there are also HC or AHC, don't use these).
|
||
|
|
- 4x 100nF ceramic capacitor (0805 package)
|
||
|
|
- 1x 10kOhm resistor (0805 package). Not critcial, just a pullup (2.2k .. 15k probably ok).
|
||
|
|
- 3x 16pin IDC (=2x8) male receptible to connect the panels.
|
||
|
|
- 1x 40pin female connector to connect to the RPi.
|
||
|
|
- 1x (optional) 22μF .. 100μF capacitor for 5V rail (either 1206 SMD or
|
||
|
|
radial electrolytic with 2.5mm pitch/6.3mm diameter)
|
||
|
|
* The Gerber FAB files are provided as [active3-rpi-hub75-adapter-fab.zip](./active3-rpi-hub75-adapter-fab.zip)
|
||
|
|
|
||
|
|
The board is also [shared on OSH Park][osh-active3] (not affiliated).
|
||
|
|
|
||
|
|
![Preview][rendering]
|
||
|
|
![Real World][real-world]
|
||
|
|
|
||
|
|
Essentially, this is connecting the output pins through level shifting buffers (they
|
||
|
|
are operated at 5V, but the HCT series chips accept 3.3V input levels from the Pi). The
|
||
|
|
strobe, OE and clock signals are separately buffered for each connector.
|
||
|
|
|
||
|
|
![Schematic][schematic]
|
||
|
|
|
||
|
|
## Optional
|
||
|
|
|
||
|
|
### Power in
|
||
|
|
|
||
|
|
The area on the left has 5V/GND input pads, that allow you to power your Raspberry Pi from
|
||
|
|
a 5V source ... which you are likely to have as you are powering the LED Matrix. This is often
|
||
|
|
more convenient than using the USB connector to power the Pi.
|
||
|
|
|
||
|
|
If you do that, there are pads to add a capacitor to smooth the supply - two footprints are
|
||
|
|
provided: C5 and C6 for through-hole or surface mount components. The value is not critical;
|
||
|
|
I usually use a 22μF/6.3V ceramic capacitor on the C6 pads.
|
||
|
|
|
||
|
|
### Choose E-Line for 64x64 panels with 1:32 multiplexing
|
||
|
|
|
||
|
|
If you have a 64x64 matrix with 1:32 multiplexing, you need to supply an `E`-address line to it.
|
||
|
|
While the Address lines `A` to `D` have fixed positions on the Hub75 connector, there
|
||
|
|
seem to be two different ways to connect the `E` address line: it is either on pin 4 or pin 8
|
||
|
|
of the connector. So this adapter board provides the flexibility to choose the right pin for
|
||
|
|
your matrix.
|
||
|
|
|
||
|
|
Look at the back of the matrix or the documentation to find out for your specific board where
|
||
|
|
to connect E.
|
||
|
|
|
||
|
|
Once you know that, the jumper area in the bottom left of this adapter board allows to choose
|
||
|
|
to which pin to connect the E-address line to. The corresponding other pin should be connected
|
||
|
|
to GND. Simply solder a wire bridge as indicated below (or use a jumper that you can change later).
|
||
|
|
|
||
|
|
If you are not using such 64x64 matrix, you can connect both these pins to GND.
|
||
|
|
|
||
|
|
Here are the typical configurations:
|
||
|
|
|
||
|
|
No 1:32 64x64: to GND | E-Line on Pin 4 | E-Line on Pin 8|
|
||
|
|
-------------------------|-------------------|----------------
|
||
|
|
![][config-default] |![][config-pin4] |![][config-pin8]
|
||
|
|
|
||
|
|
### Input for serial RxD
|
||
|
|
|
||
|
|
If you are not using a 64x64 display that occupies the E-Line, you can use the RxD serial input -
|
||
|
|
this might come in handy if you are using the display to be controlled by a serial line. Be aware
|
||
|
|
that the input requires 3.3V level, so if you have a RS232, make sure to first adapt the levels.
|
||
|
|
|
||
|
|
[rendering]: ../../img/active3-pcb.png
|
||
|
|
[config-default]: ../../img/active3-pcb-config-default.png
|
||
|
|
[config-pin4]: ../../img/active3-pcb-config-pin4.png
|
||
|
|
[config-pin8]: ../../img/active3-pcb-config-pin8.png
|
||
|
|
[schematic]: ../../img/active3-schematic.png
|
||
|
|
[real-world]: ../../img/three-parallel-panels-soic.jpg
|
||
|
|
[osh-active3]: https://oshpark.com/shared_projects/6xAD1VXr
|