BlinkLED_WithIRQ

This example demonstrates

• How to read the internal ADC
• How to show the state of charge by Blink an LED without using a timing loop delay, allowing the MCU to do other things while waiting to turn the LED on or off again.
• How to implement a simple state machine

Inspiration: This example was inspired by the public domain BlinkWithoutDelay example from Arduino.

Hardware Circuit

By default, the LED is placed on the PA6 pin* (Port A, Bit 6) with a current sink configuration.

This means the negative leg (or cathode) of the LED is connected to the digital pin of the IC, and the positive leg (or anode) of the LED is connected through a current limiting resistor to VDD.

• When the digital pin is LOW, current will flow through the LED and it will light up.
• When the digital pin is HIGH, no current will flow and the LED will turn off.

*Note: Please consult the pinout for the specific microcontroller package used to identify the correct physical pin.

Internal Peripherals Used:

• 16-bit timer (T16): Timer and timer interrupt used by time_keeper_has_timed_out() for timekeeping.

Toolchain:

• The open-source Small Device C Compiler (SDCC)
  • Requires version 3.9.0 or newer - version 4.0.0+ preferred
• The open-source Easy PDK Programmer
  • Requires version 1.3 or newer
• The open-source pdk-includes repository
  • Integrated via local copy into the include/ directory
• The open-source easy-pdk-includes repository
  • Integrated via local copy into the include/ directory
• Also requires 'make' and other common build tools

Build Commands:

make clean
make build
make size (also calls build)
make program (also calls size which calls build)
make run

Note: These commands can be chained as well. i.e. make clean program run

Customization:

Edit the variables at the top of the Makefile to:

• DEVICE: Use a different Padauk MCU (defaults to PFS173)
• F_CPU: Use a different frequency for the system clock (defaults to 8MHz, i.e. IHRC/16)

  Note: The AUTO_INIT_SYSCLOCK() macro in the STARTUP_FUNCTION() method will automatically choose the correct internal oscillator (IHRC or ILRC) and clock divider based on the desired frequency. The AUTO_CALIBRATE_SYSCLOCK(vdd) macro will install a placeholder for the correct internal oscillator (IHRC or ILRC) that the Easy PDK Programmer will use to calibrate to the desired frequency.

• TARGET_VDD_MV: Use a different voltage while calibrating the internal oscillator (IHRC or ILRC) (defaults to 4000mV)
• TARGET_VDD: Use a different voltage while the IC is operating (defaults to 4.0V)

Note: All of these variables can be changed on the command line as well. i.e. make DEVICE=PFS173 clean program run

Compatibility

This example should run on every currently known Padauk microcontroller that is supported by SDCC and the Easy PDK Programmer. A device specific include file (pdk/device/*.h) may need to be supplied for less common devices.

Build Stats

• Code Size: 380 words (760 bytes)
• RAM usage: 34 bytes + stack
  • Most of the 21 bytes are used by the millis() routines and variables (defined in the time_keeper.h include file), as well as the millis related comparison/math found in main(). Using smaller data types, or more efficient techniques, would help out if running into resource limits.