DOS is a "program loader."
Not that that's a bad thing, nor does it disqualify it from being an "operating system."
If RPi is toggling a pin at 21MHz, that's without the linux operating system being involved.
Talking to IO in fast system is always slower than the internal cycle time. Switching a pin at (relatively) high power at the edge of your circuitry and with a potentially significant load capacitance is "difficult."
(You also don't want to look too closely at how slow that RAM memory access is, on cache misses.)
OK, that is something I suspected and hoped was not true, but thanks for the information. On the Atmel chips you can get a square wave at clock divided by four, 21Mhz on a 700Mhz system is clock divided by thirty three. I was hoping that the Raspberry Pi was a cheap and simple route to working with higher throughput chips, like high-speed ADCs with parallel interfaces (e.g. 8 bit 100Msps), but I can see that was a pipe dream. I'd rather write code than figure out how to get a FPGA to work.
You might be able to connect those via the memory interface, or via some sort of DMA scheme. But you probably can't get 100MHz; that's only 10ns for each byte, which is down near the propagation delay for individual logic-gate chips...
GoForSmoke:
What you do with the data is going to make a difference. Hope it's not high-res face or voice recognition.
Nah, I had some dumbass idea to make a simple oscilloscope out of it. Just something to look at dv/dt.
westfw:
high-speed ADCs with parallel interfaces
You might be able to connect those via the memory interface, or via some sort of DMA scheme. But you probably can't get 100MHz; that's only 10ns for each byte, which is down near the propagation delay for individual logic-gate chips...
In the end if I can't get a microcontroller that can keep up I am thinking of a pure logic solution that just plows it into static RAM once the trigger voltage is hit, maybe with a CPLD or an FPGA, and then have the microcontroller read it out of memory and analyze it. I have to figure all that out, it is outside of my skill level right now but probably not for very long.
GoForSmoke:
Are you making square waves or reading waveforms?
You talkin' to ME? I will assume so...
I would be reading, not writing, if I was looking to pull data off an ADC. I was just using the data the guy posted about square waves being the likely upper limit for reading bits off the GPIO pins as well as writing to them. I am not sure if that is true, but I am going with that for the time being. My Raspberry Pi arrived from Newark today so I will have to get an image ready for it and see what it can really do.
It may be possible to read at 100MHz for long enough to take a useful sample, but getting a 100MHz ADC working well will be a challenge I think, you won't be able to play with is on a breadboard at that speed.
I played with a similar idea a while back, I eventually decided to use hardware for the sampling into external RAM and a fast uC for triggering etc.
That said some processors have a camera interface (I think that's what it's called), most notably the PICs. AFAIK this is designed to read a parallel port directly and DMA the results into memory. That may be a good option.
Isn't that a bit old? Shouldn't you be looking at ColdFire microcontrollers instead? (ok, I haven't checked whether there's a Coldfire+TPU version. There ought to be; 68332 is getting ancient!)
I have a 68331 development board around somewhere. It's left over from an actual 68331 development project that I was pretty deeply involved in (the cisco-500 Terminal Server!)
Being as the LPC1114 is the only DIP ARM around I'd say it will be a popular chip. You can get in a TSSOP as well and that will fit inside the DIP footprint IIRC. So you could make a board that allowed for PHT and SMD, one for hobbyists/protoyping and the other for production.
Coridium have loaded a BASIC interpreter, maybe Picaxe had better look out. I'd post about this on their forum but they are very touchy about posts regarding other products and they get summarily deleted.
Japan's Nissan Motor Co plans to equip some of its luxury cars with a system to control steering electronically, rather than mechanically, the first time so-called "steer-by-wire" technology will be used in mass-produced vehicles.
And, in theory, you could hook an Arduino into that too! ]
I broke down and bought a lamp/magnifier that has 36 white LED's rather than a weird circular flouro tube.
It seems whiter than my last illuminated magnifier, maybe a tad brighter as well.
Japan's Nissan Motor Co plans to equip some of its luxury cars with a system to control steering electronically, rather than mechanically, the first time so-called "steer-by-wire" technology will be used in mass-produced vehicles.
And, in theory, you could hook an Arduino into that too! ]
They may be doing it to cut cost, like replacing tactile buttons with touch screens. By the way, I tested the MPG for my car. On highway if I use cruise control I can get the advertized 38MPG at 75MPH. I was on the other hand trying my best but only got 24MPG on local roads. They promised 27MPG. I was driving like a senior citizen.
I think the CVT is very good at high speed. It shifts to a gear ratio that optimizes engine efficiency. My engine is running at 2,000 RPM or less at 75MPH. You want to always drive with cruise control otherwise if you step on the gas, the RPM goes up and ruins your MPG. But the same CVT is horrible at low speed, especially at stop to go. It easily revs at 2,000 when I was trying to get from 0 to 20MPH and then shifts down to 1,250RPM when I hit 30PMH. Maybe I need a tune-up.
Try one of the head-mounted magnifiers, they are great, a bit cumbersome but you can really see the small stuff clearly.
Rob
After getting the same advice from Grumpy Mike last year I went to Harbor Freight and checked theirs out. The one to get is the most expensive, almost $10 before the discount coupon -- I paid $7. It's got a light and has a box with 4 different double-lenses and clips on the visor I expect to hold the lens at 2 distances though you can put 2 lenses in at once (gets heavy) and maybe see germs with.
The lens flips up or down, the visor does too (and occasionally needs tightening), it's always in the right position as you move your head and it leaves both hands free. I was using a magnifier with base but the visor is so much easier to work with I won't go back. It's well worth the money or even 2x-3x what I paid.
This is the item, compare to the next cheaper one if you go there:
Try one of the head-mounted magnifiers, they are great, a bit cumbersome but you can really see the small stuff clearly.
Rob
After getting the same advice from Grumpy Mike last year I went to Harbor Freight and checked theirs out. The one to get is the most expensive, almost $10 before the discount coupon -- I paid $7. It's got a light and has a box with 4 different double-lenses and clips on the visor I expect to hold the lens at 2 distances though you can put 2 lenses in at once (gets heavy) and maybe see germs with.
The lens flips up or down, the visor does too (and occasionally needs tightening), it's always in the right position as you move your head and it leaves both hands free. I was using a magnifier with base but the visor is so much easier to work with I won't go back. It's well worth the money or even 2x-3x what I paid.