PICAXE-28X2 microcontroller

Product Details

A very popular enhanced X2 PICAXE microcontroller. Favoured in hobbyist projects due to its powerful features and capabilities, but also suitable for more advanced educational use. This is the universal voltage version 28X2 chip  (based on the PIC18F25K22).

The 28X2 supports up to 22 inputs/outputs with 16 analogue/touch sensor channels with an operating speed up to 16MHz using an internal oscillator and up to 64MHz using an external resonator or crystal. This chip supports 4 internal and up to 32 external program slots and is capable of acting as an i2c slave device.

All X2 series parts support enhanced features such as configurable i/o pins, ring tone music and touch sensor inputs, i2c, spi and high-speed serial with background receive. Scratchpad memory plus separate Data EEPROM and Data Table are supported.

Click here for more X2 series information.

For more details see the What is PICAXE and PICAXE Pinout pages.

The PICAXE-28X2 replaces the older PICAXE-28, 28A, 28X, 28X1, 28X2-5V (PIC18F2520) and 28X2-3V (PIC18F25K20) chips.


Pack size 50x10x15mm
Pack weight 4.2g

The following table gives a brief summary of the various PICAXE chips.
For a more detailed comparison please see the PICAXE manuals and pinout diagrams.

Feature 08M2 14M2 18M2 20M2 20X2 28X2 40X2
Memory Capacity (bytes) 2048 2048 2048 2048 4096 4096 4096
RAM (bytes) 128 512 256 512 256 1280 1280
Byte Variables (bytes) 28 28 28 28 56 56 56
Input/Outputs Pins 6 12 16 18 18 22 33
ADC/Touch Pins 3 7 10 11 11 16 27
Max. Freq. (MHz) 32 32 32 32 64 64 64
Serial In/Out Yes Yes Yes Yes Yes Yes Yes
Infrared In/Out Yes Yes Yes Yes Yes Yes Yes
I2C Yes Yes Yes Yes Yes Yes Yes
Tune (ring tones) Yes Yes Yes Yes Yes Yes Yes
Parallel Tasks 4 8 4 8 1 1 1
Program Slots 1 2 2 2 1 4 4

The same software, BASIC language and USB download cable is shared between all the PICAXE chips.



PICAXE-28X2 Microcontroller Datasheet PDF Datasheet
X2 Series Product Summary PDF Datasheet
Details of using 'pwmdiv' options with the 'pwmout' command on the PICAXE-28X2 Forum Link


Revision History

Current PICAXE-28X2 production firmware is version B.3 Known issues: ISSUE - SHIFTIN/SHIFTOUT IDLE HIGH MODES DO NOT WORK CORRECTLY The xxxx_H 'idle high' modes of shiftin and shiftout do not operate as expected. To workaround this issue use the bit-busting routines described in manual part 2. ISSUE - KBLED COMMAND DOES NOT WORK CORRECTLY The kbled command does not light the keyboard LEDs as expected. There is no workaround for this issue. ISSUE - NAP 1 CAUSES RESET At K31 CLOCK FREQUENCY To workaround this issue do not use 'nap 1' after 'setfreq k31' All other values (e.g. 'nap 2') work correctly. ISSUE - CALIBADC IS UNSTABLE AT >= 32MHz CLOCK FREQUENCY To workaround this issue use two consecutive 'calibadc' commands to give time for the Vref to settle. Previously resolved issues: B.3 was the first release of the PICAXE-28X2 (PIC18F25K22). Previous firmware versions were the discontinued PICAXE-28X2-5V (PIC18F2520) part.

Related Products