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_Sync_:
Yep, there are some free toolchains for almost every chip!

I'd personally prefer AVRs because I have experience coding for them and I like gcc ;)

We could discuss that for ages, it's the old Atmel,Microchip,Younameit discussion...
badSCR:

--- Quote from: _Sync_ on February 04, 2010, 10:07:53 pm ---We could discuss that for ages, it's the old Atmel,Microchip,Younameit discussion...

--- End quote ---
lol, yep we could.  So far AVR is winning in the poll for this.


I feel my skills are not high enough for me to contribute much of anything.  
But, if the specs are good enough, the price is right, and I like the design; Then i think i will probably build one.  Just now getting a lab together and looking for a job.

https://www.eevblog.com/forum/index.php?topic=187.0    (General Chat >  Whats your Work-Bench/lab look like? Post some pictures of your Lab.)

sorry, not try to hijack.
alm:
The main argument I see for using a 32-bit micro (ARM) is a graphical LCD (or OLED ;)). This might be nice for large numbers (your standard character LCD is a bit small for bench DMM IMO, and 7-segment is less flexible), dual display (like the Fluke 45) or graphs (both bar graph and histogram). I believe 8-bit micro's are a bit short on memory for this task (unless you go for the largest parts that costs more than a basic ARM). I don't have experience with ARM though, I've only used AVR.

Apart from this, an 8-bit micro should be plenty. The fastest most commercial units can sample is 2kS/s (Agilent 34401A, Keithley 2000, the most recent modules might be faster), and this is obviously at reduced resolution. A 20MHz 8-bit micro should be able to handle this unless you do tons of floating point math. I think sampling this fast is only useful in assembly line testing anyway, where you want to test a continuous stream of products. It's nice if you have a bar graph that's reasonably fast (most Flukes do 50S/s AFAIK). We will need a fair amount of I/O's though (display, buttons, ADC, relays for things like range selection, serial/USB/ethernet out).

Alson
_Sync_:
As I said, I think our major concern should be designing a usable ADC!

The userinterface and interfacing with other stuff is not really complicated.

I don't have much time on my hands now but I will look into reverse-engineering and drawing schematics for something that is based on the Keithley 196. This should provide a good basis from which we can work on...

And I agree, only fancy graphical interfaces would require a bigger ammount of computation time, but people get along with just 8-seg displays ;)
xani:

--- Quote from: alm on February 04, 2010, 10:52:00 pm ---The main argument I see for using a 32-bit micro (ARM) is a graphical LCD (or OLED ;)). This might be nice for large numbers (your standard character LCD is a bit small for bench DMM IMO, and 7-segment is less flexible), dual display (like the Fluke 45) or graphs (both bar graph and histogram). I believe 8-bit micro's are a bit short on memory for this task (unless you go for the largest parts that costs more than a basic ARM). I don't have experience with ARM though, I've only used AVR.

Apart from this, an 8-bit micro should be plenty. The fastest most commercial units can sample is 2kS/s (Agilent 34401A, Keithley 2000, the most recent modules might be faster), and this is obviously at reduced resolution. A 20MHz 8-bit micro should be able to handle this unless you do tons of floating point math. I think sampling this fast is only useful in assembly line testing anyway, where you want to test a continuous stream of products. It's nice if you have a bar graph that's reasonably fast (most Flukes do 50S/s AFAIK). We will need a fair amount of I/O's though (display, buttons, ADC, relays for things like range selection, serial/USB/ethernet out).

--- End quote ---
For me main argument in favour of ARM is not graphical LCD but fact that those micros have much more things inside, like AT91SAM7X256 with Ethernet, USB and several serial interfaces and it doesn't cost much more than similar AVR ( 10$ vs. 6$ for atmega128)
But then, if u get analog frontend right, u can use pretty much any micro u want and AVG have advantage of large community behind it (thousands of ppl possibly hacking meter ;]

Imo analog frontend should be something like i2c/SPI for adc + few lines for switching multiplexers etc. or some small cheap 8 bit micro as "controller"

So someone who want "just meter" can get some atmega8 + 2x16 LCD, few buttons and encoder, but someone else can connect 8 analog "cards" to atmega128 hooked to LCD touchscreen to create "meter to end all meters"  ;D
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