====== T02 - LED display driver ======

4-digit LED display is connected to microcontroler by the use of two serial-in shift registers with output latches [[http://www.ti.com/product/SN74LS595|SN74LS595]]. To display any information on the display it is necessary to send two bytes:

  * 1st byte represents individual segments of single LED display (D7..D0)
  * 2nd byte represents address of digit (A7..A0)

Used pins of microcontroller:

  * GPIOA9 - serial data
  * GPIOA8 - clock
  * GPIOB5 - latch

Figure 1 shows time diagram of communication between microcontroller and LED display. Bits are sent starting from MSB. 

{{ :courses:be2m37mam:tasks:shieldled2.svg |}}

Example of serial data sequence (two bytes) to show number 0 on 1st digit (from the left): ''1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1''