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7-Segment Displays Wiring
Segment Indicators, Tech Guide

7-segment LED Displays Wiring

Multiplexed connection

You can use the output multiplexer to control 16 seven-segment displays using just one controller pin.

Before assigning displays you need to "connect" output extension in the configurator - just click on the empty pin that you want to use as common output signal for all displays and click "Output MUX" button. The multiplexer will be assigned and now you can start configuring any of 16 displays.

Connect output multiplexer board as described, to 4 address lines, SIG (S) line and assigned in the configurator output control pin.

MAX7219 LED display driver and TM1637 LED display driver

Each display module build on MAX7219 driver has 3 input control signal (besides power lines) - CLK, DIN ("D") and CS ("L").
The CLK input is connected to one of 16 multiplexer otputs, with number that you have assigned in the configurator (0-15).
Two other signal inputs - "DIN" and "CS" - should be connected to the corresponding common signal lines - "D" (pin #28) and "L" (pin #27) output signals.

Display module build on TM1637 driver has 2 input control signal (besides power lines) - CLK and DIO . The "CLK" input is connected to assigned multiplexer otput, the "DIO" input is connected to the "T" signal line (pin #29), not to "D" line!

Display assembled on DM13A LED drivers or shift registers

This is convenient way to make any 7-segment display with any number of digits and digits size. With one driver you can make a 2-digit display, with two - 4-digit etc. See more details about indicators assembled on DM13A drivers. All connections are the same as for the MAX7219 driver listed above. So, you can use one multiplexer to connect up to 16 displays. The same way you can use the 74HC595 shift registers instead of LED drivers (but drivers are preferred)

Option: 8-channel extension

To extend number of 7-segment displays or serial LEDs annunciators that are located in some part of your cockpit, but you don't need more than 8 outputs, you can use 8-channel 74HC4051 multiplexer breakout board (see the right picture).

Note: if you use the 8-bit multiplexer board you should take care about the signal inputs location - it is slightly different from 74HC4067. All bus lines are used the same way as for 74HC4067, except of one address line S3 - it's not used in 8-channel multiplexer.

NOTE: the "pull-down" resistor connected to the CLK with a value of ~1...3 kΩ is used to prevent the LEDs from being randomly lit on start or because of interference between different displays connected to one multiplexer (because while multiplexer output is not selected it remains in high-impendance state and without resistor the display input connected to it is very sensitive to interference from surrounding signals ).


Option: Direct connection

In case when you need to use only a few 7-segment displays in your cockpit, or you need to add one more to assigned multiplexed ones, you can use "direct" connection, without multiplexer. The "CLK" input in this case should be connected to assigned controller pin (no need to use a pull-down resistor), other signal inputs (D,L) are the common for all output devices (pins #27,28).

Note: for direct connection only 8 pins from # 30 to # 37 of the controller board can be used (this is Port C directly controlled, for speed reason). You can assign them in the configurator, all other pins are not available for direct display control.

Here is connection diagram for MAX7219, the same is for LED drivers/registers. For TM1637 simply connect the "DIN" input to the "T" signal line:

Please don't ask if is it possible to "daisy-chain" MAX7219 modules. You can connect up to 16 displays to one single output pin using one multiplexer and common address bus lines, as described above!


Configuration

The configuration is unified for all displays, you'll only need to select display type and some additional options. All listed parameters are pre-configured for output in the correct format, with dot position, number of digits and some of the display options pre-defined.


Options

Any display can be easily configured to output more than one data value. For example, you can have 2 or 3 independent data on one 8-digit display. In the picture above you can see Bus Voltage + Bus Load on the right TM1637 display and DME distance + DME time on the upper MAX7219 display).

To display data value in the position other then the display right side, use the "Position" option, which allow you to shift least significant digit to the left. Just enter needed offset value.

To output additional parameter value on the same display, you need to select second parameter, then select the same display output pin number as for the first parameter was assigned (use the "Apeernd" button), and then enter shift position number.


Configuration Optionss

Custom text symbols

You can configure 7-segment indicator to display some custom text (as fixed text or text displayed by conditions) using these 26 symbols (along with digits and dot):

Note: this option is available since ver. 0.9.17 beta.

Text examples:

- "Ch" or "CH" (channel)
- "Pr" or "Pro" (programming..)
- "Err" or "Error"
- You can use upper line, middle line or bottom line (using the "~", "-", "_" symbols)
- Using the "*" symbol you can display degree sign (for temperature).

The text can be a part of the displayed parameter value, configured as shifted text and displayed alongside with parameter value or, it can appear in the same position, replacing the value by condition.

... examples will be added....




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