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Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
I want to program a chip to control a PWM and track two inputs (voltage and current). It does not have to do a lot. Bjorn has made some suggestions for an ARM. I have heard about a few others.
What would be good to get and who should I call (company name and product). How do I program the chip without buying expensive hardware? I have heard that some companies will give the programmer for free.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
I hate to suggest it, but you might want to look into the Arduino. It is an AVR that has a bootloader pre-loaded on it, so you can use a simple program on the computer to get code on it. There is even a nice gui program that has a code editor/compiler/uploader/etc you can get for it, and a special dumbed down version of the code to make it easy to do things like pwm and serial i/o. The bare chips with a bootloader are about $10 on ebay or the likes, the software is all free, and you can get a simple development board for them for about $20 that has the crystal oscillator, a usb-serial adapter, and a led or two.
Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
... wrote ...
I hate to suggest it, but you might want to look into the Arduino. It is an AVR that has a bootloader pre-loaded on it, so you can use a simple program on the computer to get code on it.
Why did you say "you hate to suggest it"? Is it not a good solution? Again, I am totally new at this topic.
I called the company and looked at their website. I can get the DEV-00666 which is the Arduino along with the programming board and power from a USB. I can program it on my computer and upload the software using the USB. When I am ready to move to my circuit board I can use the DEV-09218 after I have programmed it with the 09115.
Does this sound reasonable? For those that have used this chip will it do what I want? The company said it has analog inputs up to 5v, so I will have to make sure I use a high impedance voltage divider and some 5v zener clamps to keep the voltage within the range.
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
They are kind of the ipod of the microprocessor world, easy to use and wildly popular, but to anyone that has used a 'real' microprocessor and development tools they seem expensive and overrated. But for someone just getting into the hobby they are great, which is why I recommended it.
As to the dev-00666 aka 'Arduino Duemilanove', it should work great for your application. I have one myself actually, and it is a pretty good starting point. It was certainly easier/cheaper to get up and running than my PIC based system.
Just one point--if you want to move the chip off of the board you will need to add a 16MHz quartz crystal, and tie the reset pin to +5v for it to run (and of course apply +5v to the chip). Also, I would recommend getting a spare microprocessor in case you damage one (as can happen easily when working with high voltages), the project I was using mine for ( ) managed to produce a spike large enough to fry my processor--and waiting the week to get a new one was quite agonizing!
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
Does this sound reasonable? For those that have used this chip will it do what I want? The company said it has analog inputs up to 5v, so I will have to make sure I use a high impedance voltage divider and some 5v zener clamps to keep the voltage within the range.
You have not explained in detail what you want but as long as the frequencies are low enough it will do what you want.
A microcontroller can't easily make just any frequency, it can only make frequencies where the period is some multiple of the period of the oscillator. So at high frequencies the resolution is limited. The same with the analog inputs, there is a fixed limit where the sample rate can't go any higher and any frequencies above that will be lost or cause aliasing. As long as your requirements are within reason there should not be any huge problems.
There is nothing wrong with the Arduino way of doing things. The main argument against is that some gritty details are hidden from you to make everything simpler. In many cases that is not a problem but sooner or later you will wish you knew about the details.
Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
It is amazing how much one starts to learn, and then realize that something may not work. I was thinking about getting the Arduino chip. The frequency of the signal I will be analyzing is near 100khz. The chip only has analog read speeds of 10khz. I don't know the digital sampling rate.
If I want to accurately compare the phase shift of two pulses, I will need a much higher sampling rate. I think one needs at least 2x the frequency to reconstruct the pulse, but to compare the phases I would think I need a significantly higher rate, like 50-100x more? Would a PIC be the best choice then?
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
PICs have asynchronous inputs, so you might be able to use one. I know the old PIC16F84s have been used as frequency counters up in the 50MHz range! AVRs on the other hand have synchronous inputs, and can only count up to around half of the oscillator frequency. Analogue reading is even slower like you noticed.
You might want to ask NeonJohn what he did for his induction heater, I remember he made some kind of digital PLL.
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