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PICAXE FAQ:
Where can I purchase PICAXE microcontrollers?
All microcontrollers can be purchased from within the
Educational Systems>PICAXE section of the online store at
www.tech-supplies.co.uk
There appear to be two PICAXE download cables – which
should I use?
We supply two cables, both are wired identically, but
one ends with a straight 3 pin header and the other ends with a stereo
style 3.5mm plug. If making your own board we recommend the stereo cable as
it is cheaper and our sample PCB files use this connector, but either can
be used with any size of PICAXE microcontroller.
Can I make my own PCB?
Yes, we actively encourage students to make their own
boards, incorporating the download cable connector on the PCB. Sample PCB
Wizard files are available by following the links at the bottom of the
page. If you use another PCB package you can print out the image of the PCB
and then trace it!
Do I need to connect unused inputs or outputs?
No, unused inputs or outputs can be safely left
unconnected, as long as you do not reference them within your control
program.
Can I simulate my program on-screen?
If you create your program as a flowchart you can
run/simulate it on-screen. However the BASIC language has many additional commands
so it is not possible to simulate BASIC programs on-screen.
I’ve bought some blank PICs and they don’t work in the
PICAXE system!
The PICAXE microcontroller is not a blank PICmicro! It
is a microcontroller that has been pre-programmed with a ‘bootstrap’
program that enables the download via the direct cable link (the bootstrap
program tells the microcontroller how to interpret the direct cable
programming commands). Therefore you must buy ‘PICAXE’ microcontrollers,
rather than blank microcontrollers, to use with the PICAXE system. However
we sell PICAXE microcontrollers at approx. the same price as blank devices,
so there is very little price difference for the end user, particularly if
you purchase the multi-packs.
I’ve programmed a PICAXE microcontroller using a
conventional programmer and it will now not work in the PICAXE system!
You have overwritten, and hence deleted, the PICAXE
bootstrap program (see above). The microcontroller can no longer be used as
a PICAXE microcontroller, but you can naturally continue using it with your
conventional programmer.
Can you reprogram microcontrollers (that I have
accidentally erased) with the bootstrap program?
No. We do not accept microcontrollers from unknown sources
due to the correct storage/handling procedures required by these devices.
It is also likely that if we did offer this service the handling cost would
end up more expensive than new PICAXE microcontrollers anyway!
Can you supply the bootstrap program so that I can make
my own PICAXE microcontrollers?
No. The small royalty made on each PICAXE chip sold is
the only financial benefit to our company to support the PICAXE system –
the software is free and the cables/development kits are sold at very low cost.
Therefore we do not allow anyone else to manufacture PICAXE
microcontrollers.
Can I see the assembler code that is downloaded into the
PICAXE?
If you own a Revolution Serial PIC Programmer, you can
convert PICAXE BASIC programs into assembler code, to program blank PICs or
to just learn how assembler code works. However some of the more complex
commands (e.g. serin) are not supported, and the assembler code program
generated is optimised for sequential learning (not optimised for
compactness as with the PICAXE system) and so the code is not identical to
that downloaded to the PICAXE.
Can you alter the input/output pin arrangement of the
PICAXE microcontroller?
The PICAXE-08 has 5 pins that can be configured as
desired. The PICAXE-18 and PICAXE-28 input/output pin arrangements are
fixed and cannot be altered.
How long a program can I download into the PICAXE
microcontroller?
This varies on the commands used, as not all commands
use the same amount of memory. As a general rule you can download about 40
lines of code into the PICAXE-08/18 and 80 lines into the PICAXE-28.
However some commands, such as sound and serout use more memory and so will
reduce this count. In our experience most educational programs that are too
long to download are generally badly composed, and can be greatly reduced
in size by use of sub-procedures etc.
Do I need to erase the device?
How do I strop a program in the PICAXE microcontroller
running?
Each download automatically overwrites the whole of the
previous program. There is generally no need to erase the memory at any
point. However if you want to stop a program running you can select the
‘Clear Hardware Memory’ menu to download an ‘empty’ program into the PICAXE
memory.
How often can the PICAXE microcontroller be reprogrammed?
The manufacturer datasheets state the devices can be
reprogrammed at least 10,000 times. In practice this number may be much
greater.
How vulnerable to damage are the microcontrollers?
The microcontrollers have a high level of static protection built into each
pin and so handling them without any personal static protection in an
educational environment is perfectly acceptable.
Can I control servos using the PICAXE?
Yes, the PICAXE-28 system has a ‘servo’ command that allows control of up
to 8 servos (one on each output).
Can I control an LCD display?
Yes, the PICAXE supports serial LCD modules (like the Serial LCD/Clock
Module AXE033) via the serout command. Note that the AXE033 module can also
be pre-programmed with up to 8 messages to reduce the memory usage of the
PICAXE microcontroller.
How fast does the PICAXE operate?
The PICAXE-08/18 microcontrollers have an internal 4MHz
resonator, and the PICAXE-28 uses an external 4MHz ceramic resonator. This
means the microcontroller processes 1 million assembler commands a second,
which equates to roughly about 10,000 BASIC commands per second.
How do I create time delays longer than 65 seconds?
The best way of creating long delays is
to do minute delays with a loop, e.g. to wait an hour (60 minutes)
for b2 = 1 to 60 ‘start a for..next loop
pause 60000 ‘wait 1 second
next b2
‘next loop
The PICAXE microcontroller works at a nominal 4MHz, but
due to device manufacturing tolerances there is likely to be a drift of a
few seconds over long time periods (e.g. a day). Note that the Serial
LCD/Clock module (AXE033) has a precision clock and ‘alarm clock’ function
that can be used to trigger the PICAXE at predefined interval or at certain
time/dates with much greater precision.
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