How to Use PICAXE-28A: Examples, Pinouts, and Specs

The PICAXE-28A is a versatile microcontroller designed for educational and hobbyist projects. It features 28 pins, enabling multiple input and output connections, making it ideal for controlling a variety of electronic devices. The PICAXE-28A is programmable using a simple BASIC-like language, which makes it beginner-friendly while still offering enough functionality for advanced users. It is commonly used in robotics, home automation, sensor-based systems, and other interactive electronic projects.

The PICAXE-28A microcontroller offers the following key technical details:

• Operating Voltage: 4.5V to 5.5V
• Clock Speed: 4 MHz (internal resonator)
• Programming Language: BASIC-like syntax
• Number of I/O Pins: 28 (including digital and analog pins)
• Memory: 256 bytes of EEPROM for program storage
• Communication Protocols: Serial (via programming cable)
• Power Consumption: Low power, suitable for battery-operated devices
• Package Type: DIP-28 (Dual Inline Package)

The PICAXE-28A has 28 pins, each with specific functions. Below is the pin configuration:

Note: Some pins have dual functionality, such as supporting analog input or PWM output. Refer to the PICAXE datasheet for detailed pin-specific capabilities.

1. Power Supply: Connect the VDD pin to a 5V power source and the VSS pin to ground.
2. Programming: Use a PICAXE programming cable to connect the Serial In and Serial Out pins to your computer. Install the PICAXE Programming Editor software to write and upload code.
3. Connecting Peripherals: Attach sensors, actuators, or other devices to the I/O pins. Ensure that the connected devices operate within the voltage and current limits of the PICAXE-28A.
4. Code Upload: Write your program in the BASIC-like language supported by the PICAXE-28A. Upload the code using the programming software.

• Power Supply: Ensure a stable 5V power supply to avoid erratic behavior.
• Pin Protection: Use resistors when connecting LEDs or other components directly to the I/O pins to prevent damage.
• Programming Cable: Use the official PICAXE programming cable for reliable communication.
• Debugging: Use the Serial Out pin to send debug messages to your computer for troubleshooting.

Below is an example of a simple program to blink an LED connected to pin B.0:

' Blink an LED connected to pin B.0
' The LED will turn on for 1 second and off for 1 second in a loop.

main:                     ' Define the main program loop
  high B.0                ' Set pin B.0 to HIGH (turn LED on)
  pause 1000              ' Wait for 1000 milliseconds (1 second)
  low B.0                 ' Set pin B.0 to LOW (turn LED off)
  pause 1000              ' Wait for 1000 milliseconds (1 second)
  goto main               ' Repeat the loop

Explanation:

• high B.0: Turns on the LED by setting pin B.0 to HIGH.
• low B.0: Turns off the LED by setting pin B.0 to LOW.
• pause 1000: Introduces a delay of 1 second.

1. The PICAXE-28A is not responding to programming commands.

   • Solution: Check the programming cable connections. Ensure the Serial In and Serial Out pins are correctly connected to the computer.
   • Tip: Verify that the PICAXE Programming Editor software is installed and configured correctly.

2. The microcontroller behaves erratically.

   • Solution: Ensure a stable 5V power supply. Check for loose connections or short circuits in the circuit.

3. Connected devices are not functioning as expected.

   • Solution: Verify that the devices are compatible with the PICAXE-28A's voltage and current ratings. Use pull-up or pull-down resistors if required.

4. The LED does not blink in the example code.

   • Solution: Double-check the LED polarity and ensure it is connected to pin B.0 with a suitable resistor.

• Q: Can the PICAXE-28A handle analog inputs?
  A: Yes, some pins on Port B support analog input. Use the readadc command to read analog values.

• Q: What is the maximum current output per pin?
  A: Each I/O pin can source or sink up to 20mA. However, the total current for all pins should not exceed 90mA.

• Q: Can I use the PICAXE-28A with batteries?
  A: Yes, the PICAXE-28A can operate with a 4.5V to 5.5V battery pack. Ensure the voltage remains within this range.

• Q: Is the PICAXE-28A compatible with Arduino shields?
  A: No, the PICAXE-28A is not directly compatible with Arduino shields due to differences in pin layout and programming.

This documentation provides a comprehensive guide to using the PICAXE-28A microcontroller effectively. For further details, refer to the official PICAXE datasheet and programming manual.