This library for Arduino or Energia is designed to interface with the 74'4511 BCD to Seven Segment LED driver chip. The library also supports the use of an optional 74HC164 parallel out serial shift register to reduce output pin requirements.
The library supports either one or two 7-segment displays.
A reference design which can be used with the library is available in the extras/hardware folder.
For a single digit, a minimum of 5 output pins are required:
- BCD bit 3 (msb)
- BCD bit 2
- BCD bit 1
- BCD bit 0 (lsb)
- /LE (Latch Enable)
- You can also optionally define the /LT and /BL signals
For two digit setups, a minimum of 6 output pins are required:
- BCD bit 3 (msb)
- BCD bit 2
- BCD bit 1
- BCD bit 0 (lsb)
- /LE_1 (Latch Enable for most significant digit)
- /LE_0 (Latch Enable for least significant digit)
- You can also optionally define the /LT and /BL signals
To reduce output pin usage with the 74HC164, the library assumes that the '164 pins are connected to the '4511 pins as follows:
164 4511
--- ----
QH -> D0
QG -> D1
QF -> D2
QE -> D3
Output pins QA - QD are not used. A and B input pins should be tied together and are controlled by the "DATA_IN" pin.
For a single digit, a minimum of 3 output pins are required:
- CLK
- DATA_IN
- /LE (Latch Enable)
- You can also optionally define the /CLR ('164), /LT ('4511) and /BL ('4511) signals
For two digit setups, a minimum of 4 output pins are required:
- CLK
- DATA_IN
- /LE_1 (Latch Enable for most significant digit)
- /LE_0 (Latch Enable for least significant digit)
- You can also optionally define the /CLR ('164), /LT ('4511) and /BL ('4511) signals
In the serial configuration, it is possible to control the decimal points (8th segment) of the LED displays by using the unused output pins on the 74HC164 chip. Connect QD to the most significant decimal point driver signal and QC to the least significant decimal point driver signal. Note that both decimal point driver signals need current-limiting resistors, just like all the other LED segments controlled by the '4511 BCD chip.
To control the decimal points, first store the values with the setDP(ms, ls) method, and then call writeBCD() to send the values out the shift register and change the decimal point control lines.
See the sketches included in the examples folder.
First, include the library header file:
#include "LED744511.h"Next, create an LED object. There are multiple forms for the constructor, depending on the configuration and whether you are using one or two 7-segment digits.
LED744511 myLED(BCD3, BCD2, BCD1, BCD0, BCDLE);This creates a single-digit 7-segment object which does not control the /LT or /BL pins (they are assumed to be tied high). It uses 5 output pins.
LED744511 myLED(BCD3, BCD2, BCD1, BCD0, BCDLE, LT, BL);This creates a single-digit 7-segment object which also controls the /LT and /BL pins. It uses 7 output pins.
LED744511 myLED(BCD3, BCD2, BCD1, BCD0, BCDLE1, BCDLE0);This creates a two-digit 7-segment object which does not control the /LT or /BL pins (they are assumed to be tied high). It uses 6 output pins. BCDLE1 is the most significant digit (tens) and BCDLE0 is the least significant digit (ones).
LED744511 myLED(BCD3, BCD2, BCD1, BCD0, BCDLE1, BCDLE0, LT, BL);This creates a two-digit 7-segment object which also controls the /LT and /BL pins. It uses 8 output pins.
LED744511_Serial myLED(CLK, DATA_IN, BCDLE);This creates a single-digit 7-segment object which does not control the /LT or /BL pins (they are assumed to be tied high). It uses 3 output pins.
LED744511_Serial myLED(CLK, DATA_IN, BCDLE, CLR, LT, BL);This creates a single-digit 7-segment object which also controls the /CLR, /LT and /BL pins. It uses 6 output pins.
LED744511_Serial myLED(CLK, DATA_IN, BCDLE1, BCDLE0);This creates a two-digit 7-segment object which does not control the /LT or /BL pins (they are assumed to be tied high). It uses 4 output pins. BCDLE1 is the most significant digit (tens) and BCDLE0 is the least significant digit (ones).
LED744511_Serial myLED(CLK, DATA_IN, BCDLE1, BCDLE0, CLR, LT, BL);This creates a two-digit 7-segment object which also controls the /CLR, /LT and /BL pins. It uses 6 output pins.
Once you have created an LED744511 or LED744511_Serial object, the following methods can be used to control the displays:
void writeBCD(int value)Writes value to the display. When used with the LED744511_Serial object, the writeBCD() method will also change the decimal point control signals if QD and QC are connected to the decimal point control lines. See setDP() below.
Negative values blank the display.
On a single-digit display, a positive value is displayed modulus 10. For example, a value of 22 will be displayed as 2.
For two-digit displays, there is a mechanism to display a leading blank or leading zero for values less than 10.
- To display a leading blank, then use a value less than 10.
- To display a leading zero, then use a value from 100 to 109.
For example:
writeBCD(-1)will blank both digits of the display (all segments off)writeBCD(9)will display a leading blank and the digit 9:9writeBCD(109)will display a leading 0 and the digit 9:09
void lampTest(int onoff);Enables or disables the /LT (Lamp Test) signal. Since it is an active-low signal, a value of 0 will turn it on, and a value of 1 will turn it off.
This function only has an effect if the LT pin was defined in the constructor.
void blankDisplay(int onoff);Enables or disables the /BL (Blank Display) signal. Since it is an active-low signal, a value of 0 will turn it on, and a value of 1 will turn it off.
This function only has an effect if the BL pin was defined in the constructor.
void clr74HC164(int onoff);Enables or disables the /CLR (register clear) signal on the '164 chip. Since it is an active-low signal, a value of 0 will turn it on, and a value of 1 will turn it off.
This method is only available in the LED744511_Serial object, and only has an effect if the CLR pin was defined in the constructor.
void setDP(int ms, int ls); This method sets the most signifcant (ms) and least significant (ls) decimal point stored values when using the LED744511_Serial object type (the values default to zero when an instance is created). This command does not change the decimal point control signals itself. You must follow this with a writeBCD() to actually change the decimal point signal levels.
The software and other files in this repository are released under what is commonly called the MIT License. See the file LICENSE in this repository.