Suggestion of which PIC to use

[zevon8]

I have a project in mind that would use a PIC driving logic level FET's to flash lamps. The lamps would flash at one of 2 different intensities. The intensity would be set by reading a CDS cell. There would be 5 PWM output channels, and which of the 5 PWM outputs are on being determined by membrane switches. All five channels would flash at the same time, smae PWM rate, when selected.

I have seen a similar setup using a 16C54C, but am not sure if this is the best chip for the job.

I have all the input / output combinations and states worked out, flash rate, PWM ratio, interface hardware, FET's, etc, I just need to select a chip, and start programming.


Any suggestions appreciated.

 

[Nigel Goodwin]

I have a project in mind that would use a PIC driving logic level FET's to flash lamps. The lamps would flash at one of 2 different intensities. The intensity would be set by reading a CDS cell. There would be 5 PWM output channels, and which of the 5 PWM outputs are on being determined by membrane switches. All five channels would flash at the same time, smae PWM rate, when selected.

I have seen a similar setup using a 16C54C, but am not sure if this is the best chip for the job.

I have all the input / output combinations and states worked out, flash rate, PWM ratio, interface hardware, FET's, etc, I just need to select a chip, and start programming.

The 16C54 is a very old, low end, OTP PIC - not really suitable for anything these days!.

The 16F628 (or any of the FLASH/EEPROM PIC's) will easily perform any job the 54 could do. If you choose one with A2D (like the 16F88), it would be even easier.

 

[zevon8]

Thanks Nigel, I was wondering just how old the '54 was.

Most of the requirements for the design are pretty straight-forward ( methinks ) , such as the CDS cell being connected to a transistor, so that it is set to switch at a certain light level, so A2D may not be needed for that. The only real challenge is getting PWM at 2 frequencies, and scanning the 5 membrane switches ( matrix ) to see if any have been pressed.

The idea is to have a flashing sequence occur, ( PWM based on the hi/low from the CDS cell circuit ) appear on up to 5 outputs depending on which switches have been pressed.

I am currently doing this with discrete gates/comparators, but modifying any parameters is such a hassle, changing time constants, redoing logic, you get the idea.

I was hoping to do a more generic design based on a PIC, so I could alter flash rates, levels, sequence, etc all in code, leaving the circuit alone.

From some rough designs, I think I could get what is now a PCB with about 60 components down to around 20 or less.

I have d/l the MPLAB software, and have barely started to use it. What I was wondering is, if there are any really basic programs available that I could play with so as to have something tangeble to work with as a starting point. Doesn't matter what they do, it's just that I am a practical experience kind of guy, and seem to learn faster when I have something to work with. even something that, say makes an output go high when an input appears. Does Microchip have any fragments on their site? Or is there any really basic stuff to begin with on your site? ( I had a quick look but wasn't sure what I was looking for yet )

Thanks for your response!

 

[Nigel Goodwin]

Thanks Nigel, I was wondering just how old the '54 was.

Most of the requirements for the design are pretty straight-forward ( methinks ) , such as the CDS cell being connected to a transistor, so that it is set to switch at a certain light level, so A2D may not be needed for that. The only real challenge is getting PWM at 2 frequencies, and scanning the 5 membrane switches ( matrix ) to see if any have been pressed.

The idea is to have a flashing sequence occur, ( PWM based on the hi/low from the CDS cell circuit ) appear on up to 5 outputs depending on which switches have been pressed.

I am currently doing this with discrete gates/comparators, but modifying any parameters is such a hassle, changing time constants, redoing logic, you get the idea.

I was hoping to do a more generic design based on a PIC, so I could alter flash rates, levels, sequence, etc all in code, leaving the circuit alone.

From some rough designs, I think I could get what is now a PCB with about 60 components down to around 20 or less.

I have d/l the MPLAB software, and have barely started to use it. What I was wondering is, if there are any really basic programs available that I could play with so as to have something tangeble to work with as a starting point. Doesn't matter what they do, it's just that I am a practical experience kind of guy, and seem to learn faster when I have something to work with. even something that, say makes an output go high when an input appears. Does Microchip have any fragments on their site? Or is there any really basic stuff to begin with on your site? ( I had a quick look but wasn't sure what I was looking for yet )

Thanks for your response!

There are a great many application notes on the MicroChip website, which are always worth a look.

I take it you don't have access to the C54 source code?.

 

[Jay.slovak]

You can use almost any PIC from 16F or 18F series...
16F628 is good choice, it only misses AD.. If you are looking for more pins, go for 16F877.

16C54 was the pioneer of Microchip, but now it's retired...

 

[zevon8]

There are a great many application notes on the MicroChip website, which are always worth a look.

OK, sounds good, I'll have a look at what's there

I take it you don't have access to the C54 source code?.

Unfortunately, as Jay.slovak said of the '54, the person that wrote it is also retired, so I am starting fresh. Might be a good thing

thanks!

 

[Nigel Goodwin]

Unfortunately, as Jay.slovak said of the '54, the person that wrote it is also retired, so I am starting fresh. Might be a good thing

Didn't he leave the source code?, or even a HEX file used for programming the chips?.

 

[zevon8]

The programming/developement was done on a really old IBM PC, running DOS, and it has succumbed to age also. It hosted an emulator board for other micro's also, but there is a hardware problem preventing it from booting. I believe the hard disk ( 540 meg :shock: ) to be the issue.

The biggest obstacle to ressurecting the old hardware is that the hard drive uses an ESDI controller card, so taking the drive to another PC may be a big hassle, or I would try and read it on another machine.

There are some print-outs of what appears to be code dumps, but being on thermal paper, they have faded to the point of pretty much complete illegibilty.

( I get all the fun projects :wink: )

 

[Nigel Goodwin]

I won't mention the word 'backups' :lol:

Oops! - too late!.