PICAXE Labels (20M) LAB055 ?

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moxhamj

New Member
Underneath it lists a 20M under the 14M and none of the existing picaxes are missing in the list so maybe it is not a misprint? In which case, a very interesting find!
 
lbenson

lbenson

Senior Member
If a 20M would have the same limited code space as a 14M or 08M, I personally would as soon skip it. Now, a 20X1--there you'd be talking.
 
hippy

hippy

Ex-Staff (retired)
Well spotted tarzan.

If my research is right ( no beta version here if such a thing exists ), Firmware version 3.A, 256 program size shared with data as per 08M/14M.

My guess would have been 16F685, 16F687 or 16F689. Those would be logical developments from the 16F684-based 14M. My money's on 16F685, unfortunately that doesn't have I2C/SPI/UART where the other two do.

In Programming Editor 5.1.7, press F1 (Quick Syntax Check), "Applies to..."

Looks like we all missed the clues of the 20M's arrival !
 
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manuka

Senior Member
Mmm-a 20M- this makes a round dozen PICAXE offerings (some of course now run out). MicroChip announced new 20 pin PICs 18 months ago => http://www.anglia.com/newsarchive/1369.asp?article_id=2244 ... Naturally we all hanker after more horsepower & features, but the 18X usually fits the bill at this mid range level, with the 28X1 for fire breathers. What happened to the 28X2? IMHO,as even the Easter 2007 released 14M has yet to take wing, such a 20M (especially if DIP) may fragment the market and bewilder? This is especially an issue with ever harassed educational buyers. Stan
 

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Technical

Technical

Technical Support
Staff member
You're an observant lot! Yes the 20M will be launched in February.

The biggest market for the M range is our educational market. We've had feedback that many school student projects, although quite simple, often like to use more than 5 inputs. The X and X1 parts are sometimes not an option for this type of educational use because they contain many extra features not utilised in these simple educational projects, which adds slightly to their cost. This is a very important budget factor when a school is buying, say, 300 at a time.

We also need to move with the times, as Microchip improve their technology parts change and newer devices get cheaper. For instance the base PIC microcontroller used for the original 18 is now far more expensive than the base PIC to be used for the 20M - yet the 20M provides more memory, better resolution ADC and more i/o pins.

So the 20M provides almost exactly the same features as the 08M/14M but with a fixed 9 inputs (0-7 + RXD) on left and fixed 9 outputs (0-7 +TXD) on the right. However it does not provide the same advanced functions (i2c etc) as an 18X, which will still be the medium size chip of choice for most hobbyists. We do not expect to sell many 20Ms outside of the educational market.

Stan, your table and figures are very out of date, the 14M is actually a very big seller and some of the chips listed in your table are not even for sale any more!

The recommended 2008 line up is

Educational
08M
14M
20M

Standard
18X
28X1
40X1

Professional (coming in the summer)
28X2
40X2

08, 18, 18A will still be available for those who want to continue using them.
 
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hippy

hippy

Ex-Staff (retired)
I can understand the worry over market fragmentation and confusion. Anyone who visits Microchip's site to choose a processor will know just how difficult too much choice can make.

I was pleased to see the 28X1 replace the existing 28 series. I'd also like to see the 18 series replaced by a single 18X1 and all PICAXE's converge ( rationalised ) to having the same abilities as each other ( as best the PICmicro hardware will support ).

While a price differential remains though it's not likely; people still want cheap and will accept difference in capabilities and commands as the price of that. The 28X1 wins there because the 16F886 is better and cheaper than all it replaced.

I think cost is more important than chip size for the overwhelming majority so if the 28X1 were as cheap as the 08, Rev-Ed could reduce the range to just 28X1/40X1. Control is not in Rev-Ed's hands though.
 
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Mycroft2152

Senior Member
The 20m seems a very logical step for the education market. Many school projects seem to include driving a 7 segment LED display. With 9 outputs, this will now easily be accomplished.

Also the 20M could easily be the basis of a multiplexed multidigit display.

For the model rocketeers, the 20M could be a single chip countdown sutstem with audible conituity and ignition (9 outoputs)!

The 64 thousand dollar question is; "Will the 20M footprint be compatible with the 14M and 08M footprints?"

That would make a very flexible protoboard.

Myc
 
Peter M

Peter M

Senior Member
coming in the summer ??

Ummm.... Technical I gather you mean summer in the UK (around June) for the release of the x2 parts?
 
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manuka

Senior Member
Technical- thanks for a breakdown of 2008 offerings. Any price points for this 20M? This is actually pretty crucial "down-under", as our academic year starts in early Feb. & budgets are already being drained!

I've no apologies for that overview table (which is clearly labeled DRAFT & shows R for runouts), as it's meant to be a features reference for PICAXEs past & present - I'm continually pointing folks to it. I'll look to add the 20M but would be delighted to offer a more up to date/complete version if available. Stan
 
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inglewoodpete

Senior Member
If you've been waiting as long as some forum members have for the X2s, any summer will do!

Let's hope that hippy is right on the choice of PIC. The 16F685 has 4k of flash which means there is a good chance that the user program could be stored in flash. The 256 bytes of program space in the 08M and 14M is very restrictive. A 20M with only 256 bytes of program would confine it the education arena.
 
hippy

hippy

Ex-Staff (retired)
@ Mycroft2152 : If 16F68X, the electrical footprint is compatible, although how that pans out regarding pin numbering remains to be seen. Having numbered the 14M LHS inputs from bottom to top would mean re-runumbering pins in-program or having them out of order on the 20M chip pinout.

@ inglewoodpete : 256 bytes shared code and data only from my investigations no matter which the PICmicro used is. Although the 16F68X have 4K Flash it's not self-writable.
 
hippy

hippy

Ex-Staff (retired)
From F1 ( Quick Syntax Check ) it also looks like we're due to get a new SERVOPOS command which I guess allows servos to be udated at anytime without restarting the 20mS frame to avoid jitter etc. That should please the R/C crowd. It appears it will be available for all PICAXE's which support SERVO.
 
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Tricky Dicky

Senior Member
20M Price and pinout

Revolution included a four page Spring 2008 Newsletter in the IEE magazine - Electronics Education. An exact price for the 20M was not quoted except to say that the education price for bulk purchases (presumably 50 units at a time) would come in at less than £1 each. They also included a pinout diagram.

Richard
 
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manuka

Senior Member
The IEE Spring 2008 mag. itself is on line (free) as a ~10MB download => http://www.theiet.org/education/supportteachers/electronicseducation/ & it includes a VSM based article (P.30-) by Clive. Since it was apparently a paper based insert, the Rev.Ed newsletter mentioned above is not shown...

Footnote: This colourful high quality IEE seasonal mag is well worth both educators & motivated students browsing & submitting to, & you may even score some points by adding "IEE contributor" to your CV ! The rationale behind this relates to IEE (Inst. Electronics Education) being confusingly very akin to the ultra prestigious IEEE (Institute of Electrical and Electronics Engineers)- the world's leading professional association for the advancement of technology! When the chips are down on a job short list, the harassed interview team may well fumble the "E" number to your benefit- I've seen this exact blunder happen in fact.
 
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manuka

Senior Member
TD: Thanks! I've sliced off the key 08M/14M/20M juicy bits (below)-note the "favourable" footprints. IMHO the PIC16F685 looks the likely PIC engine. Stan
 

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lbenson

lbenson

Senior Member
Stop the madness

Until Rev-Ed releases the details we are free to treasure-hunt and speculate. Below is a chart of what appear to be the 5 Microchip (tm) candidates for the PICAXE (tm) 20M. Below them are 6 implemented PICAXES, the 14M, 28X, 40X, 18X, 28X1, and 40X1. I had thought that hippy's analysis of the unavailability of more than 256 memory lines in the prospective 20M were based on the lack of "Self-write" capability. But while the 18X, with 600 lines of code, had that, the 28X and 40X did not, and they also had 600 lines of codespace. So it seems possible that if 20M is based on one of the larger (and up to 20 cents more costly) candidates, with 7K of program space instead of 3K, we might still hope for more space for PICAXE programs.

@hippy--or did you have another reason for thinking the candidate chips could not go above 256 lines?

@technical--since the horse has left the barn, and we have the pinouts, any reason not to provide more info?

@stan--if the 685 is the winner, can we please have more codespace?
 

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hippy

hippy

Ex-Staff (retired)
According to my 16F873A/874A (28X/40X) datasheets they both have self-write and would not be viable without that. I think the raw data for that thumbnail is wrong in that respect.

There's no magic way to self-write if the PICmicro doesn't support that so the larger Flash would only be useful for extra Basic commands. The 16F690 would have been best choice IMO, delivering I2C and high-speed serial, but if target market cost and simplicity is the prime concern then lowest price to be 14M compatible with six extra pins makes sense.
 
lbenson

lbenson

Senior Member
The raw data from the thumbnail on the 16F683A and 16F684A (with "No" in the "Self-write" column) came from a chart on the Microchip site:

http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1002&mid=10&lang=en&pageId=74

But the datasheets rule. I'm thinking about a 14M "core duo", finding that 256 lines aren't enough to do even relatively simple processing on 8 inputs and 8 outputs. That does complicate the coding, tho. Hate to use a $12 part (28X1) when a $2 or $3 part comes so close.
 
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demonicpicaxeguy

Senior Member
i'd like to see a picaxe based on somthing in the 18f range that stores the user program in the program memmory but on power up copies it to ram and executes it from there it would make a pretty quick picaxe

i'm got a hinkering that the x2 range might actaully be based on the 18f series

couldn't drop a few hints could we technical?
 
hippy

hippy

Ex-Staff (retired)
Yes, the X2's are 18F2420 and 18F4420.

Copying Flash to Ram is only possible if there's a lot of Ram and even on the 18F's that's still often in short supply. Reading token code from Flash isn't really that much slower than reading from Ram. The best gains would come from reworking the token code format so it was faster to decode but that could be quite extensive work.
 
Technical

Technical

Technical Support
Staff member
PIC16F677-I/P

PIC choice is based on a range of points, the main ones being:
1) memory type and capacity
2) raw PIC cost in bulk (we buy hundreds of thousands each year, and the costs do vary considerably at this quantity!)
3) programming/testing dwell time
4) target use (i.e. target sell price)

The 677 is the most cost effective choice for the M series commands.
i2c etc is not supported on M series parts - for this you need an X part.

The 20M supports all the 08M/14M commands with a couple of exceptions:
1) the i/o pins are always fixed so 'let dirs' (dirsc) etc. are not required
2) the 20M does not support pwm/pwmout/hpwm
3) it does additionally support the 'serrcv' command

Apart from this it is very similar to the 14M, supporting all the usual servo, serout, tune, pulsout type commands and with 256 byte capacity, around 80 lines of BASIC code.
 
hippy

hippy

Ex-Staff (retired)
I was way off mark with the 685 then. I'd discounted the 677 with just 2KW of Flash and 128 bytes of Ram, but it's testimony to just how much one can cram into a small PICmicro.

Any reason Leg 3 / Input 7 doesn't support ADC ? I'm guessing it's because it's on a different port and makes the Firmware just too complex for the slight gain.
 
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Mycroft2152

Senior Member
Hippy, It was a good call.

The 15% price difference between the chips is significant at the volumes Rev-Ed purchases. As they said in the IEE artical, the target is under 1 pound per chip in tube quantities for the educational market.

Also, the 20M is more of a "stretch" M chip rather than a "super" M chip. Though a "super" M chip would be really excellent.

Its's going to be interesting to see what Rev-Ed offers for project boards based on the 20M.

Myc
 
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manuka

Senior Member
PIC16F677! Like Hippy I'd considered the 128 bytes of RAM too small...

Technical (or anyone)- does an official PICAXE overview chart exist? Something in the style of mine at => www.picaxe.orcon.net.nz/pcxtype11.jpg (which I'll keep adding to unless better options exist) would be VERY helpful. I continually run into otherwise switched on folks who haven't a clue about PICAXE offerings, & even some electronics teachers still think only a single type (the initial 08) exists. You know how it goes- they attended a course back in 2003 & developed reliable modules, lesson plans & worksheets to suit, so why change or upgrade?

Technical minds tend to work best when they can ponder pathways/maps of possibilities of course. IMHO,as we now have a dozen of your darlings (with 14 when X2 arrive), something in a graphical "bill of fair" style would be very well received. For inspiration, & since you are a "Best of British" firm, consider the ~24 variants of the WW2 Spitfire => www.supermarine-spitfire.co.uk/spitfire_variants.html . The Mk XVIII seemingly matches the PICAXE-18X in fact!
 
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