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ARMing a Breadboard – Everyone Should Program an ARM

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Re: ARMing a Breadboard – Everyone Should Program an ARM

#51

Post by kefka »

ju-st wrote: post #49
kefka wrote: post #25

Earlier quoted context omitted.

That's not true. They are just hidden. Stm8, $1.28 http://m.aliexpress.com/item/32351992629.html Stm32, $3.06 http://m.aliexpress.com/item/1568685935.html Edit: my phone did a stupid.

Nice! So there is basically no reason to buy Atmega anymore (for me, at least).

The only reason is network effect.

Most "shields" and devices are tested and libraries made easily available for Arduino/Atmel 324P. Going to ARM means having to rebuild some of your toolkit, or finding it.

But again, it's ARM. And the "more expensive one" is 32bit.

Re: ARMing a Breadboard – Everyone Should Program an ARM

#52

Post by d9fb698e010974b »

analog31 wrote: post #34
d9fb698e010974b wrote: post #32

Earlier quoted context omitted.

Others are suggesting power supplies, but I think you can just use a voltage divider from a 5V supply. Like maybe a 2.7K resistor followed by a 5.6K to ground?

It needs to be regulated, because the microcontroller draws varying amounts of current. But a simple regulator is just a three-legged IC and a capacitor.

Ah okay, I didn't realize that.

Re: ARMing a Breadboard – Everyone Should Program an ARM

#54

Post by mikechml »

pcwalton wrote: post #37
0xcde4c3db wrote: post #10

If you're interested in low-level code (assembly, JITs, Forth, etc.), note that official documentation for the ARM ISA has considerable encumbrance. It's not like most architectures where you just go to the manufacturer's website and download a PDF of the programming manual; ARM makes you register an account and agree to a rather restrictive clickwrap license (something to the effect of "you're only allowed to use th…

The situation still isn't great, but this has gotten better over time with the documentation on infocenter.arm.com, which Google usually pulls up as a top result when you search for various ARM instructions. For example, Googling for "arm tbl" brings up this: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.... which contains links to the rest of the AArch64 instruction set. The documentation has scary "Su…

It's only got the "Superseded" notices because it's an old version, if you browse to the latest one in the menu on the left they're not there.

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc....

Re: ARMing a Breadboard – Everyone Should Program an ARM

#56

Post by vardump »

Animats wrote: post #55

That's a nice little part, but it has very limited memory: 32 kB on-chip flash, 4 kB RAM. That's less than some Atmel ATMega-based Arduinos. The Arduino Due (an ARM CPU) has 512 KB flash, 96KB RAM. To get more memory, though, you have to go surface-mount.

4 kB RAM + 32 kB flash is plenty for a lot of projects, assuming it's possible to execute directly from flash. Just attach SPI flash for extra data storage.

Re: ARMing a Breadboard – Everyone Should Program an ARM

#57

Post by shortsightedsid »

ChuckMcM wrote: post #13

I too am often surprised at how often people reach for an Atmel 8 bit AVR chip rather than an ARM. It is a testament to the momentum that Atmel built, the avr-freaks community and the amazing cost effectiveness of it all. But now we're seeing ARM chips with built in clocks, and fewer base components required and I think the end of that AVR dominance is on the horizon. And that is why Dialog is buying Atmel[1]. Gettin…

I'm using a PIC12 in product that replaces an existing one. At Volume Pricing 8 Bit PICs are pretty much incomparable to ARMs. A quick check on Digikey shows that for 10000 pieces, the cheapest 8 Bit Micro is a PIC10 - 35Cents/Unit (that's for today only). ATTiny is about 2 Cents more but that can change. The cheapest 8051 from Energy micro is in the same range as well.

The cheapest ARM Cortex M3/M0 or even a ARM7 is $1+. When you are shipping products (and not doing a hobby project), BOM cost is a major factor. If you sell a Million Units each with a micro in them, the cost difference is about $700,000. Even keeping cost aside, size matters. The smallest 8 Bit micros from Atmel or Microchip or any 8051 is around 3x3mm. Most ARM micros are much larger.

Rule of thumb that I use is to pick the micro by function, price and size. Sometimes a 8-Bit micro is more than enough for the job. Buying something that costs more, bigger in size and for which the MHz is not an advantage is an overkill.

Having said that, a companion product that also working on requires the MHz and so, a Cortex-M3 fits perfects there.

Re: ARMing a Breadboard – Everyone Should Program an ARM

#58

Post by yuubi »

ajross wrote: post #8
Turbo_hedgehog wrote: post #5

Earlier quoted context omitted.

You can also use a voltage divider if you are willing to suffer a bit of leakage current. That's just 2 resistors.

The linear regulators we are talking about are basically voltage dividers with feedback. They aren't significantly more efficient than your design, though they are ton less noisy.

Because of that feedback, you get to use your load as the lower half of the divider, so the total current drawn from the source is the load current plus a few microamps for the regulator's internals.

In the passive voltage divider circuit, if the load varies its current draw, you have to have a resistor in parallel with the load so that the total current through both the load and the resistor doesn't vary significantly (where "significant" is derived from your tolerance for voltage variation).

Re: ARMing a Breadboard – Everyone Should Program an ARM

#59

Post by NonEUCitizen »

d9fb698e010974b wrote: post #30

This is really cool. One cautionary thing though. I think that because of breadboard capacitance if you try any sort of high frequency stuff on the breadboard (like >= 10MHz) you'll get all sorts of weird effects. (This is just a breadboard problem that occurs at high frequencies, not an ARM problem). I'm just an amateur in this area, so if someone who is more knowledgeable could confirm or deny with I wrote above th…

1. Others estimate higher max frequency. This one's on the high side of estimates:

http://dangerousprototypes.com/2011/12/05/breadboard-limitat... [might have to ask EE friends about transmission line termination at those frequencies]

2. See also this video (and comments on video) where they measure:

https://www.youtube.com/watch?v=6GIscUsnlM0

Re: ARMing a Breadboard – Everyone Should Program an ARM

#60

Post by TD-Linux »

ChuckMcM wrote: post #13

I too am often surprised at how often people reach for an Atmel 8 bit AVR chip rather than an ARM. It is a testament to the momentum that Atmel built, the avr-freaks community and the amazing cost effectiveness of it all. But now we're seeing ARM chips with built in clocks, and fewer base components required and I think the end of that AVR dominance is on the horizon. And that is why Dialog is buying Atmel[1]. Gettin…

One of the reasons that 8-bit AVRs are still popular is that the architecture was specially designed for C - compared to many other popular 8-bit microcontrollers, it has a C-style stack, lots of registers, and low latency for most instructions. The 8-bit PICs are much less amenable to C compilers.

I also use the ST micros for most of my projects, but the AVR is also a great device with a well supported toolchain - I think it's generally easier for most beginners due to easy to use peripherals and simpler clock trees than the ST chips, while still being production-ready.

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