PICAXE

Key takeaways

PICAXE belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect PICAXE to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of PICAXE from memory before moving on to harder problems.

Reference excerpt

PICAXE is a microcontroller system based on a range of Microchip PIC microcontrollers. PICAXE devices are Microchip PIC devices with pre-programmed firmware that enables bootloading of code directly from a PC, simplifying hobbyist embedded development (similar to the Arduino and Parallax BASIC Stamp systems). PICAXE devices have been produced by Revolution Education (Rev-Ed) since 1999.

Hardware There are currently six (6) PICAXE variants of differing pin counts (8-14-18-20-28-40) and are available as DIL and SMD. PICAXE microcontrollers are pre-programmed with an interpreter similar to the BASIC Stamp but using internal EEPROM instead, thus reducing cost. This also allows downloads to be made with a simple serial connection which eliminates the need for a PIC programmer. PICAXE is programmed using an RS-232 serial cable or a USB cable which connects a computer to the download circuit, which normally uses a 3.5 mm jack and two resistors.

Programming language PICAXE microcontrollers are programmed using BASIC. The PICAXE interpreter features bit-banged communications:

Serial (asynchronous serial) SPI (synchronous serial) Infrared (using a 38 kHz carrier, seven data bits and five ID bits) One-wire The "readtemp" command reads the temperature from a DS18B20 temperature sensor and converts it into Celsius. All current PICAXEs have commands for using hardware features of the underlying PIC microcontrollers:

Hardware asynchronous serial Hardware synchronous serial Hardware PWM DAC ADC SR Latch Timers (two on X2/X1 parts which have settable intervals, only one on M2 parts with a fixed interval, older parts have none) Comparators Internal temperature measurement

Program space All current PICAXE chips have at least 2048 bytes of on board program memory available for user programs:

08M2 - 2048 bytes 14M2 - 2048 18M2+ - 2048 20M2 - 2048 20X2 - 4096 28X1 - 4096 40X1 - 4096 28X2 - 4096 per slot with four slots for a total of 16 KiB 40X2 - 4096 per slot with four slots for a total of 16 KiB

Clock speeds The default clock speed for all M2 and X1 parts is 4 MHz and for the X2 parts is 8 MHz. The SETFREQ command allows speeds from 31 kHz up to 8 MHz for X1 parts, 31 kHz up to 32 MHz for M2 parts and 31 kHz up to 16 MHz for X2 parts (up to 64 MHz for the 20X2) using the internal resonator. An external resonator can be used with the X1 parts for from 4 MHz to 20 MHz clock speeds and with the X2 parts for 16 MHz to 64 MHz clock speeds.

Project boards Project boards for different applications are sold by Rev-Ed which contain the PICAXE, download circuit and may also contain a prototyping area or high power output drivers.

Software Revolution Education develop software for writing programs for PICAXE.

PICAXE Programming Editor PICAXE Programming Editor is a Windows-only IDE for writing PICAXE programs in BASIC code or a simple flowchart. PICAXE Programming Editor features:

source code colour syntax highlighting auto indentation syntax check and program download code explorer to shown variable, label and constant values full on screen simulation with animated chips and line by line code highlighting simulation breakpoints by line number and variable value debug and serial terminal windows AXE027 download cable testing and port identification tools various testing tools such as the analogue calibration wizard various code generation wizards (pwmout, tune, RTC setting, etc.)

AXEpad AXEpad is a cross-platform application recommended for Linux and Mac users. It lacks some of Programming Editor's wizards, simulation and MDI.

Logicator for PICAXE Logicator is an easy-to-use shareware flowcharting program. The Logicator web page is out of date as the free version does support all commands but shows nag screens. PICAXE Programming Editor 6, the successor to PICAXE Programming Editor 5, has Logicator flowcharting merged into it so separate Logicator software is no longer required. Like PICAXE Programming Editor 5, PICAXE Programming Editor 6 is freeware.

Third-party software

Yenka Yenka is a program developed by Crocodile Clips Ltd which has flowcharts and simulation.

Others Many companies and organizations have put out their own editors with special features. Some include language translators or serial connectors, so there is a wide variety of consoles to be used.

Support Support is available at the Technical Support section of the PICAXE website and at the PICAXE Forum. The PICAXE Forum has a finished projects section where completed projects and PICAXE programs are posted, plus there is a similar section on the PICAXE website.

See also Arduino BASIC Atom BASIC Stamp Maximite OOPic KodeKLIX - PICAXE chip based snap-together educational system

References

Illustrations

Worked examples

Example 1 — a first encounter with PICAXE

Start with the simplest possible case. Write down what PICAXE claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to PICAXE before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about PICAXE ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of PICAXE

In research: PICAXE appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses PICAXE in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: PICAXE is common in secondary-school and first-year university syllabi. It links to neighbouring topics Microchip Technology hardware, Microcontrollers, so understanding it makes those chapters shorter.
In everyday life: Look for PICAXE outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study PICAXE in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what PICAXE means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain PICAXE out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is PICAXE in simple terms?

PICAXE is a microcontroller system based on a range of Microchip PIC microcontrollers. PICAXE devices are Microchip PIC devices with pre-programmed firmware that enables bootloading of code directly from a PC, simplifying hobbyist embedded development (similar to the Arduino and Parallax BASIC Stam…

Why does PICAXE matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study PICAXE?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on PICAXE.