LED Blinky Tutorial

FPGA's and SoC can be used for many more advanced functions as making a LED to blink. However "LED Blinky" is considered a "Hello World" for systems that can not otherwise say Hello.

Requirements

To make LED to Blink (under user control) following requirements are needed:

1. Some Programmable Device: MCU, CPU, CPLD, FPGA, SoC
2. Working Programming or Configuration interface or means to boot the Programmable Device
3. Timing Source (Clock), can be external or internal, must be be enabled
4. Active Power to all required power domains of the Programmable Device
5. Release of main Reset
6. LED Connected to some user controllable I/O Port of the Programmable Device
7. LED must be assembled with right polarity and proper current limiting resistor
8. Valid I/O Voltage applied to the I/O Bank with the user LED

If any of those requirements are missing, you will most likely fail with the simple task to get an LED to Blink.

Programmable Device

Timing Source

Valid I/O Voltage

It is very common that modern Integrated Circuits have separate power supply pins for I/O Voltage. That voltage if applied control the output levels from the device, if the Voltage is too low or missing then it is not possible to have enough current from the device I/O Pin to make a LED Lit.

FPGA and SoC SoM's can have fixed and user controlled Voltages for the I/O Banks. It is important to assure that the I/O Bank that controls the LED has a valid Supply Voltage applied.