Learning to use PICS

Hi Dave, Since you're experienced with the BASIC Stamps, you might consider PicBASIC

or one of the other BASIC compilers. The commands are more-or-less the same, but you can buy your PIC processors for a few dollars in the temp range that you need. You'll need to build/buy a programmer. I made a "picall" programmer, and use the free software for it:

Not quite as fast or code-space efficient as assembly - but much better than the Stamps.

You can try out PicBASIC free at

There are also a few BASIC compilers available free for the AVR's - sorry, no links for those.

Arch

Hi Dave,

You should take a look at the Atmel AVR microcontrollers. The C compiler is free (GNU GCC) and they don't need any special programmers. You just connect them to the parallel port of your PC and then you can program them. You can program them in different ways if you need to and they're supported by different programming languages. You can see a simple AVR project I did here:

I've used PIC microcontrollers quite a lot and I think the AVR's are better (and cheaper). But if you're determined to use a PIC then something like the PIC16F874 is a good place to start. It has a lot of the features offered by other microcontrollers (USART, PWM, ADC, Timers, etc etc). You'll need a programmer of somesort, the PICSTART Plus is a common one but it's probally cheaper to make your own. This site has a homemade programmer (do a google for others):

A free assembler and IDE can be downloaded from the Microchip website. It's called MPLAB. They also offer a restricted C compiler for free. You have to pay for the complete C compiler.

PIC's are good, but I would recommend the Atmel AVR's.

Hope that helps,

Craig

"David Harper" schreef in bericht news: snipped-for-privacy@posting.google.com...

Dave,

Look at

A lot about PICs, PIC programming and PIC program developement. Plus links to other interesting PIC sites.

petrus bitbyter

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So those compilers allow standard PICS (from Microchip Technologies) to be programed in BASIC? How much slower is a PIC program in BASIC than assembly?

Thanks! Dave

Is C the only language they're programmable with? The reason I ask is that I'm a mechanical engineer by job and major, so I have not (yet) learned C.

Thanks! Dave

There is a good PIC tutorial (13 pages) that covers PIC assembly programming. There are only 35 instructions to learn.

And for good hardware prices, look at Randy Jones site at

Most of his pics are less than $3.

-Bill

Here is a nice list of references:

If you are looking for basic, I'd stick with the stamp. However, I find it cheaper and easier to program in assembler.

A nice reference site is

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Regards,
   Robert Monsen

"Your Highness, I have no need of this hypothesis."
     - Pierre Laplace (1749-1827), to Napoleon,
        on why his works on celestial mechanics make no mention of God.

compiler is

The AVR's do support other languages. The 2 most common (for any microcontroller) are assembler and C. Because the AVR C compiler is free, most AVR examples are programmed in C. A lot of PIC examples are programmed in assembler just because the assembler is free. PIC assembler is very very easy to learn whereas AVR assembler can be a bit more involved.

If you want to get the most out of your microcontroller then you should consider either assembler or C. Assembler is lower level than C and so offers you more control. But well programmed C can be just as good as assembler and has the advantage of being more readable (and portable if that matters). Also, trying to program complex problems in C is much easier (and therefore less prone to error) than assembler. If you already have experience of programming in BASIC and you understand the idea of registers, then moving over to C isn't so daunting. You also have the advantage of various programming newsgroups who can help you solve any problems you encounter.

My advice is take the plunge and learn C using an AVR microcontroller. The whole setup will cost no more than £10. And once you've got some experience with C you'll be able to program whatever you want.

Dave,

You're going to get 10,000 suggestions. But given your situation I would suggest taking a look at the XC Structured Basic Compiler (XCSB) by Sergio Masci. It's a highly optimized Basic along the lines of the Stamp. So migration is easy. Since it is compiled, you should get much better performance than the Stamp. Also you can load it into the 16F chip of your choice. I would suggest the 16F877A if you have the space.

While you stated in another post that you didn't want limited software I would strongly suggest that you try before you buy. XCSB has a limited Lite version that will let you test our some ideas. Then if everything works you can purchase the standard or pro edition of the software.

If you're willing to spend some time learning another language, and BTW no matter what you do you'll be learning another language to some degree, consider JAL. This Open Source, Pascal like, compiled HLL primarily targeted to the PIC has a large following and lots of libraries for doing different things. Also it's completely free and without restriction.

Finally you can always go back to the source and write PIC assembly. As you step into the wider PIC world you'll find that lots of code and examples are written in PIC assembly. So having at least a reading knowledge of it can be helpful.

One last interesting place to look is Myke Predko's Basic87X interpreter. Like the microcomputer BASICs of old (C64, TRS-80, Apple II) the interpreter , program code, and parser are all embedded on chip:

There are lots of resource links. Hope these help:

JAL and XCSB can be found on my PIC langages page:

Jal's Open Source page is here:

Lots of resources on the PICLIST website:

hope this helps,

BAJ

Hi Dave, You can write your BASIC code, and then compile it into a standard ..HEX file - with which you can program any PIC of your choice (TONS to choose from for just a few $$ each!).

There are a bunch of different BASIC compilers for both PICs and AVRs. Some are more efficient - but all will run much faster than the Stamps. I don't have much experience with 'pure' assembly, so can't compare speed of the BASIC compilers to ASM - but from things I've heard the BASIC compilers run maybe 25 - 50% slower depending upon how complex your code is.

Arch

Everyone, Thanks for the help so far. I have a question in regards to speed. I'm trying to figure out how to equate clock speed (for SPI/3-wire interface) to oscillator speed. From what I've read, it's adjustable...? I'm basically wondering how much faster the clocks are for various PICs. The Basic Stamp clock speed is about 16.6kHz, and I'm wondering how PICs (or Amtel's chips) compare?

I've also eyed the SX chip from Ubicom, distributed by Parallax. Anyone have any experience with those?

Thanks in advance! Dave

-Everyone,

-Thanks for the help so far. I have a question in regards to speed.

-I'm trying to figure out how to equate clock speed (for SPI/3-wire

-interface) to oscillator speed. From what I've read, it's

-adjustable...? I'm basically wondering how much faster the clocks

-are for various PICs. The Basic Stamp clock speed is about 16.6kHz,

-and I'm wondering how PICs (or Amtel's chips) compare?

The BS clock speed is actually 4 Mhz. The 16.6Khz speed is probably the speed of interpretation.

As for SPI if you use the hardware SSP module you can clock it up to the instruction rate of the chip. For a 20 Mhz part this is

5 Mhz. It's fast.

-

-I've also eyed the SX chip from Ubicom, distributed by Parallax.

-Anyone have any experience with those?

None personally. It's a 75 Mhz low end PIC clone. Doesn't have flash, so you'd have to have to go the programmer/eraser route.

JAL, which I mentioned before has Ubicom support. May give you an avenue for HLL development for a really really fast chip.

But you may be overstating the speed issue. Some 18F PICS can be clocked at 40 Mhz giving a 10 MIPS instruction rate.

Fast chips + fast hardware can lead to unbelievably performance. Working with the Stamp is like driving an earth mover in terms of speed. Raw PICs will feel like a high performance sports car in comparison, while the SX will feel like a rocket.

BAJ

This depends on three things (1) the person doing the programming in assembler, (2) the BASIC compiler and (3) the complexity of the problem.

A good BASIC compiler WILL produce code that is within 10-20% of that produced by an experienced assembler programmer. If the assembler programmer is not very experienced then a good BASIC compiler WILL produce code that is MUCH more efficient.

As the complexity of a problem increases so too does the ability of a good compiler to outperform the assembler programmer. The compiler is a tool that enables the computer to automatically perform hundreds of thousands of tests on your code. A good compiler will search for optimisations that an experienced assembler programmer would find laborious and a non-experienced assembler programmer would not even know about. Most importantly, the compiler can do all this work each and every time you make a change to your program. An assembler programmer would typically only look at a small part of the program when he changes it.

Some compilers convert BASIC source code into a special internal form that requires an interpreter to run. This internal code is downloaded into the PIC and then processed by an interpreter that is running on the PIC. Each instruction in the BASIC program is effectively executed by the interpreter. If the instruction is executed 10 times in the BASIC source then it will be executed 10 times by the interpreter.

Some compilers convert BASIC source code into machine code which is the same stuff that assemblers produce. A mediocre compiler will generate several machine code instructions for each BASIC instruction. A good compiler will combine multiple BASIC instructions and generate fewer machine code instructions.

Programs executed by an interpreter WILL run much (several hundred times) slower than an optimised machine code executable produced by a good compiler that produces machine code.

The XCSB compiler will convert the following to just 6 machine code instructions:

proc inline set_bit(ubyte *addr, ubyte id) *addr = *addr | (1

Looks like "C" to me. I know this must be so, as I can't understand it :-). Yet I can easily read the 'Proton','CH-flash', 'iL_Bas16' etc Basics. regards john

It supports pointers like "C" but unlike many C compilers for the PIC it doesn't generate a ton of code to build and pass the pointers and then dereference them if it can determine the address at compile time. PEEK and POKE would be more in keeping with other BASIC dialects but pointers allow the programmer to give the compiler more information which in turn helps the compiler trap silly errors and generate better code.

The reason I chose the above example is because it shows how the compiler converts some very complex functionality into very tight code

Regards Sergio Masci

- optimising PIC compiler FREE for personal non-commercial use

Assembly language programmers do that in 3 instructions.

and

allow

the

No they could not.

They could rearrange the code to give the equivalent of:

clear_bit(&b, 2)

if test_bit(&a, 1) then set_bit(&b, 2) endif

Then yes the assembler programmer could reduce it to 3 machine code instructions but in this case the XCSB compiler would then generate 4 machine code instructions (still infinately better than many other PIC compilers).

BUT THIS IS NOT THE SAME AS THE ORIGINAL CODE

In the original, bit 2 of "b" follows bit 1 of "a" exactly, in the rearranged code bit 2 of "b" will glitch (temporarily change from 1 to 0 and back to 1) when bit 1 of "a" is 1. If "b" is used to send messages to an interrupt service routine this may cause you problems, also if "b" is an alias of an I/O ports this WILL cause you problems.

The XCSB compiler will not perform this kind of optimisation behind your back because there are MANY ways that it could cause problems.

Regards Sergio Masci

- optimising PIC compiler FREE for personal non-commercial use

All, I appreciate everyone's suggestions and help so far. Right now I've started diving into understanding the architecture and memory of a typical PIC (16C84), which I figure is the best place to start. After that, I figure the programming will be a lot easier to understand.

The program memory I understand, no problem (like the BS2, only it seems only instructions can be written at these locations for PICS, and only during programming).

However, with the data memory allocation, I'm having some difficulty based on some of the online datasheets:

and beginner guides (from piclist.com):

From what I've read, there are 2 banks each divided into 128 registers. The first 12 registers are SPR, which more or less define the chip's current state. The next 32 registers are GPR (like RAM?). What are the next 88? It's defined as "unimplemented data" according to Fig 4-2 in the 16C84 datasheet.

Secondly, figure 4-7 (pg 18) shows 4 banks, not just two... just how many banks are there for this chip? Can it be more than 2 banks for different PICS, which is why they're showing it as 'off limits', so to speak?

Lastly, back in figure 4-2, it states the 36 GPR in bank 1 are mapped to bank 0. Does this mean they're connected, and if a GPR in bank X changes, then the same GPR in the other bank will change also? If so, are any of the SPR connected in this fashion?

Thanks for the patience if you've made it this far, and I really appreciate the help!

Dave

Secondly

The part you picked is ultra anchient. Might I suggest a 16F88. I have a page on rationale here:

Correct to a point. Chips like the 16F88 are self programmable, so they can write their own program memory. This leads to the possibility of a bootloader where there is no true programmer because the chip programs itself. Note that you have to use a traditional programmer to get the bootloader onto the chip.

They give you access to periperals such as the timer and I/O ports. Later chips have a bunch more.

RAM. An ultra limited amount too.

As specified. Nothing there. Unusable.

Right.

Yes.

Some. For example the STATUS register is usually mapped into every bank.

No problem.

But I beg of you not to get caught with the 16C84 or 16F84. They are older than dirt. The newer chips bring a lot to the table, and cost less than the older chips. Take a read of my page for more info.

BAJ