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Looking For PWM Chip That Can Be Controlled From The Serial Port Of A Computer


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I am looking for chip that has serial control (Copressor) that i can control from a computer with PWM outputs and i need a total of 24 outputs for L.E.D.s, 8 for red, 8 for green and 8 for blue. I will probably have to use more than 1 chip that is fine as long as i can control them by software or they are addressable so they have their own identity. If the chips have other features for RGB control that would be great! I also need to be able to dim each output to be able to do color mixing.

I have used the PakV chip from A l Williams but have had some address pin issues and they are not willing to enlighten me as to what could cause the chip to fail just by setting the address pins, these chips cost $25.00 each and i have had problems with 2 of them.
Kevin Roach

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I do not know enough about the chips you already have used to make a comparison; but you can talk to a microcontroller through the serial port and you can certainly send out data bits to the port pins to control PWM devices. PWM is simply a matter of "ON" times vs "OFF" times. You would not need additional chips for 24 outputs. This is only 3 ports. The biggest overhead is coding the port pins to do what you want.


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Do you have a microcontroller in mind that would work? Is this a hardware PWM or software PWM? Yes i understand PWM that's why i chose PWM as a control standard for RGB L.E.D. Control. 24 outputs from 1 chip seems like an awfull lot, but if you have a chip in mind i'm ready to listen.

Maybe i need to clarify my lighting, i need 24 outputs for 8 modules with 3 leds each, 1 red, 1 green & 1 blue. I want all 8 molues to be able to change to any color at any time by computer control.

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You will not find a micro with this many hardware PWM options, but you can configure any pin as a software based PWM. On a micro with a port A, portB, port C, and Port D, there are 8 pins per port. You would use the RX and TX for your communication. this would still leave you with 24 pins using outputs of 3 ports for your PWM control and 6 pins left over which can be used as specific inputs for other tasks. Or, you could skip the whole RS232 thing and add a keypad and display.
One such chip that will work is the ATMega16. You can get chips with even more outputs than this one.

If you want a chip with PWM channels, Atmel has one with 10 PWM channels. It is the AT90PWM3.

Here is a link where you can get a comparison of all:



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