Re: TI-H: More AVR Qs
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Re: TI-H: More AVR Qs
>> 500kHz clock (saves power and gives you a little processing power)
>
>No, in this case it will be digital.
You could get away with a real slow clock.
>Specificly I have two
>phototransistors, one sensing ambiant light, one sensing ambiant + the light
>from a 2-5mW laser pointer at about 15M. The ambiant light sensor is
>bypassed with a resister, output of the sensors is fed into a comparator,
>the output of which will be read by the AVR.
The comparator compares two voltages, so you'd have to have a refrence.
Each AVR pin can supply 20ma. If you tie two together...
>This gives me 4 parts for the sensors, two phototransistors, a quad
>comparator and a resistor.
>Since the 1200 has an onboard analog comparator, and my phototransistors
>pass 20 mA at saturation, would it work to connect the emiters of the
>phototransistors to the 1200's comparator input, and the collectors to one
>or more port B or D pins? The docs say that those pins can source some
>current, but not how much.
>This would eliminate the need for the external comparator chip.
>> You can put SRAM on a 1200 though it only has a 3 layer stack.
>
>How do you communicate with an SRAM chip?
Address, data, output enable, write enable... Any SRAM doc will have the
timing available.
>Is that the communication protocol that would be the simplest to use with an
>external EEPROM?
3 wires is better than 20. :)
Marshall will give you free samples of their I2C eeprom. Look for the
atmel parts.
You could also use DataFlash. for ~$4 you get 512kbyte and a SPI interface.
>Perhaps I should rephrase that, since you think building a mini-webserver
>with an AVR is not difficult :)
Well :) , all you have to is make a software uart that uses the external
interrupt for receive and the timer for clock...but all that work has
already been done. You can either get a software uart or software
interrupt uart from atmel's www site.
If you REALY need serial, the 2313 is $1 more and has a hardware uart.
>Would it simply be a matter of hooking up the MAX232, connecting it to some
>pins on the AVR and pasting in some already written AVR code?
Yes.
>Or am I going
>to have to write AVR code to handle receiving bits myself?
One of the first things I did was to use their UART code. That must have
been 2 years ago. Its gotten better since then.
>> MAX232 works fine. Get them free from maxim-ic
>
>Thanks for the refrence, I was acutally having trouble finding them locally.
Free samples!!!
>Another question, other than the fact that it is a HLL, do you have any
>information about the E-LAB Pascal compiler product? It is a pascal
>compiler that will compile code for the AVR2313 and up (and several PIC
>micros).
There is a $99 C compilier for the AVR. There are also a free "Keep it
simple yet powerful" pascal compiler. I use IAR C to program insanely huge
programs and use ASM modules where C is too slow.
>Obviously the code it generates will not be as efficent as hand-coded ASM,
>but since few of my projects will require that kind of efficency, I'm
>considering using it where possable.
Your logging thing could use it. The AVR runs rings arround what you need
to do. :)
>The problem is that it doesn't work on the 1200 (I'm making a guess that it
>needs the onboard SRAM).
It needs a real stack.
>I was kind of hoping that someone might know of a
>way I could use the code it generates anyway, or of another free HLL for the
>AVR (I prefer pascal but micro compilers are all pretty easy to learn, so
>thats not a requirement. Free or usable demo is a requirement. E-LAB
>pascal is limited to <4k code in the demo, but thats not a problem for me).
Hua? Do you mean write a routine and use the ASM thats generated?
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