Can anyone recommend a good AVR book...

... for a beginner?

And what's the difference, anyway, between the AVR and the ATxxxxxxxx series of chips?

TIA

Michael

Reply to
mrdarrett
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AVR is so simple, you don't need a book. Just get a development kit and go through some examples on line and off line.

Which AT? Generally speaking, ATtiny, ATmega and AT90 are similiar AVRs.

Reply to
linnix

Ah, so the AT90Sxxxx series is also an AVR... thought it was something completely different.

So, about that book... ;-)

Michael

Reply to
mrdarrett

Hello Michael,

Seriously, as Linnix wrote, you may not need one. I started with the TI MSP430, thought about buying a book but after taking a look at one I realized how fast some of the contents become obsolete. By the time it's printed there is a slew of new uC variations that are now used by everyone.

Main things to get started: Learn the design environment, play around, try to make the blinky-LED work, try to change blink rates or pattern, load again and so on. Then study the family guide and the data sheet for a long, long time. After that you know all the assembler words the uC of choice understands and what they mean. Even if you never do assembler you need to become familiar with the peripherals on board and how they can affect or impair each other.

If you really want a book recommendation I'd post again at comp.arch.embedded where among many uC experts there is also Ulf Samuelsson from Atmel. I am sure he'd know which books are good. Ulf is very responsive, I wish TI and others would participate as well.

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

Ah ok. (Actually until you menti Michael

Reply to
mrdarrett

Try avrfreaks.net I think there is a tutorial on there.......

Reply to
martin.shoebridge

[snip...snip...]

There is some slop-over, with the relatively new AT90CAN128 chip being an almost identical twin to the ATmega128.

All you really need to get started is, say, an ATmega8, an AVRISP programmer or the STK500 (if you don't have breadboards and bench power supplies handy), a copy of the free AVR Studio, and the device manual. The individual chapters in the manual do a good job of explaining how to tickle the various peripherals. The on-line help in AVR Studio handles the assembler and instruction set.

Like Joerg, I typically approach a new processor with the embedded equivalent of "Hello, world!": get one pin to toggle at an intended rate using one of the chip's timers and an interrupt service routine. That's enough to validate that I grok the toolchain, can create a runnable image and get it loaded, and can sling around the necessary bits to handle ISRs and I/O. From there, the rest is just coding ...

--
Rich Webb   Norfolk, VA
Reply to
Rich Webb

On 27/09/2006 the venerable Rich Webb etched in runes:

You can also download a demo version of a C compiler from the Imagecraft website. It's free for 45 days and then becomes code limited to 8K which is still fine for the mega8.

--
John B
Reply to
John B

The latest version of Atmel's AVR development environment works together with winavr. This means that you can write a C program and single-step it in the simulator, watching register, memory and i/o port values.

One thing to watch out for if you use a serial in-circuit programmer - it is easy to lock yourself out of the device by setting the fuses incorrectly.

In particular, setting the watchdog timer to "continuous" prevents reprogramming of the device or even the watchdog fuse!

John

Reply to
jrwalliker

I Agree with the others, but If you still want a reference book for programming in C the AVRs, I can recomend you this one: Embedded C Programming and the Atmel AVR Authors are Barnett, Cox &Ocull you can get it from B&N

Reply to
Simon Dice

Ok, thanks for the reference.

I think I'll try and build my own programmer. I'll try the ATTINY11-6PC: $0.53 each at Mouser. What a deal! At this rate I can buy more than one, in case I burn it out.

I've found some schematics for a programmer out here:

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I think the pinout is compatible with the AT90S2323, but I'll check the data sheets on the ATTINY11 to make sure...

Questions:

1) For the parallel port, is Pin 1 the pin on the upper-left looking at the Printer Port on the PC, or the upper-left looking at the Printer Cable (IOW, upper-right looking at the PC)?

2) Let's say I want to make a simple AA battery tester (0 to 1.5 VDC range), and interface it to the PC via serial port. I know I'll need an ADC, and I can probably get away with using the one on the chip (comparator, right?). Anyone have any schematic for building such an AVR-to-Serial interface?

fwiw, I went over to Borders last night, and even the PIC books didn't discuss in much detail how to interface with the PC. Just only how to interface the programmer with the PC. Sheesh.

Thanks!

Michael

Reply to
mrdarrett

Yes, a Max232

Here is a battery charger with RS232 and LED read out. The LEDs are time multiplexed and maintain a rather constant brightness across voltage range of 2.4V to 2.8V (two NiMH cells). It's using the Atmega169, but should work with 165 (cheaper) as well. The basic components are:

165/169 Max232 w/ 5 Cs Analog power filter (L, C and 2 R) LM317

SMPS is optional Analog multiplexer is not needed.

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Reply to
linnix

A Maxim part? From previous threads, I think I should stay away from those...

Pretty neat! You used a drive bay, huh. I couldn't find the schematics on your site though. I'm mostly interested in the serial output circuitry. Is yours a bit-banger?

Michael

Reply to
mrdarrett

Ah, I think I'm starting to get it. Use a dedicated RS-232 chip. And here I was banging my head against a wall trying to figure out how to build my own.

Well, surprisingly, Mouser actually seems to have a few MAXIM 232s in stock...

Hmm... if I'm going to use an output chip to control my computer interfaces, maybe I should just bite the bullet and look for a USB output chip... any suggestions? ;-)

Thanks!

Michael

Reply to
mrdarrett

OK, I should say TI, ST or Sipex RS232 driver chip.

Yes, charging batteries while working on the PC, and logging the charge/discharge behaviours of the cells.

I don't have one either. I went directly to layout from specs.

No, the 165/169 has hardware UART on pin 2 (RX) and 3 (TX).

AVR pin 2 to 232 pin 10 and AVR pin 3 to 232 pin 11

Reply to
linnix

The AT90USB128 is almost pin compatible with the 165/169/329/649. Unfortunately, you have to rewire pin 2 to 5 for USB and RS232 to other pins. Actually, we simply bring out the pins to vias and wire them for either chip. This is a lousy design by Atmel. I wish there is a AT90USB128/Atmega649 combo.

Reply to
linnix

Looks like the AT90USB128 is about $14 from Digikey. A (Texas Instruments!) MAX232 is about $0.90. For a beginner, I think I'll stick with RS-232. (Should be easier to write the software for the PC side too.)

Thanks a bunch.

Michael

Reply to
mrdarrett

We won't be buying that much, but the qty 10K price is $2 to $3.

Reply to
linnix

In sci.electronics.design snipped-for-privacy@gmail.com wrote: [snip]

The ATtiny11 has no RAM, only registers. C really needs some RAM for its stack, or you have to do some funky things to make it work at all. You can't have much fun with just 32 registers to store all your data (this paragraph contains more than 8x that much data). The small ones really are incredibly limited.

Best advice for a hobbyist: Buy big. Considering the cost of shipping, it's a false economy to buy the really low-end chips. You'll end up making another order very soon when you find your first project is larger than you expect. What you though was a saving ends up as being more profit for FexEx.

I'd suggest an ATmega8 (or two) and a few matching sockets - you can then swap the chip from project to project (no need for the sockets if you don't plan to solder stuff together yet, a breadboard is one big socket!). The ATmega8 has a UART, which means it has hardware to make talking to a PC's serial port easier[1]. It has a good amount of RAM and flash, which means you can use things like C's printf function to make life easier (printf and associated gubbins takes up around 2.5K of flash). It has multiple timers, plenty of pins, PWM and a bunch of other stuff you'll soon find you want.

[snipped a question]

You can use a comparator (gives a signal when one input has a higher voltage than the other) as an ADC, but you have to use it to measure the time it takes for the voltage you are measuring to charge up a capacitor to some reference voltage. You have to provide the capacitor, reference voltage, code to time it accurately, coded to turn that exponentially varying number into a linear voltage and make sure the current you take charging the capacitor doesn't affect what you're trying to measure (this method has a low input impedance - it puts a significant load on what you're measuring, changing it in the process). It takes two pins and you can only measure one voltage with your one comparator. This is not much fun, though it can shave a few cents of the price of your device, which might be worth it if you want to make a million of them. I doubt you want to make a million of them. Buy a chip with a proper ADC built-in; no external components, very little code, more accurate results, multiple inputs which take just 1 pin each and you can connect the pins directly to virtually anything without it affecting what you connect to (the ADC inputs have very high impedance). Don't connect the inputs to anything outside the AVR's supply range (0-5V probably, but you have some choice in the matter) though, or you'll fry it.

For the battery, connect - to circuit ground, + to an ADC input on the AVR. The AVR's ADC can then measure the voltage with half a dozen lines of code. That wouldn't actually make for a great battery tester; there's more to testing batteries than just measuring the voltage, but that's another subject.

Best to use the serial port, as that's by far the easiest. You might need a USB-serial converter if your PC doesn't have serial ports. Sending raw bytes is most efficient, but you'd then have to write software for the PC to decode those bytes. Much easier to just buy a nice big AVR and use printf to send ASCII text, at least at first. You can then use something like Hyperterminal on the PC and get text output on screen with minimum hassle. You can do clever, efficient protocols and squeeze them into the really cheap AVRs when you've learnt some more.

[1] You will need a MAX232 or equivalent chip to convert the AVR's 0-5V serial port (UART) signals to the +/- 15V RS-232 signals a PC serial port expects - remember to buy the 4 capacitors such chips require too, if you don't have that kind of thing lying around. You need to think about the cable from the chip to the PC as well.

If you haven't already, check out AVRFreaks. There is a lot more there than there may appear to be at first.

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Tim

Reply to
Tim Auton

-=snip=-

-=snip=-

Thank you for taking the time to give very good advice to us newbies. I appreciate it.

I think you're right. ATmega8. For about the price of a Six Dollar Burger at Carl's.

Michael

Reply to
mrdarrett

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