ICD2 Variable VPP?

[William At MyBlueRoom]

Your MAX232 doubler is really quite elegant but I'm interested in this PIC 1-chip solution for my ICD2-USB clone which will not have a MAX232 serial port on it.

Mike

What firmware do you hope will run on it?
Are you going to write custom programming software?

Given you can avoid the MAX232 with 2N7000s but you still need a VPP source.

The simple version would need at least PIC 16F876A + 12Fxxx (PWM & A/D) for the SPI to VPP boost converter (I like this solution, a few more parts (PIC, fet & choke) and one more chip to program though) Or a pair of 9V batteries I've seen done on the EPIC programmer. Cheap & cheerful but batteries yeech.

I like my take on Mr Stoltzs programmer (Inchworm) , simple & cheap. The VPP is very basic and if I could build it with less parts I would have.

Add programmable VPP would be nice, another choice is a simple switch with a couple of diodes inline to drop the voltage by another 1.4v

Again it's just a hobby grade programmer, IMHO much better than most roll your own programmers (except you need a preprogrammed PIC)

 

[Mike - K8LH]

Bill,

I'm building a USB only version of the new MC ICD2 based on the discussion/research on EDABoard. It uses an 18F4550 and a 16F877A (just like the new MC ICD2). Both PICs are programmed with bootloader firmware. Actually, I think the 18F4550 file we have contains an operating system too.

So, it's simply an inexpensive USB ICD2 "Inchworm", of sorts (grin), which is powered from the USB port.

Mike

<added>

I'd still like to hear about your L-C Meter.

 

[William At MyBlueRoom]

Bill,

I'm building a USB only version of the new MC ICD2 based on the discussion/research on EDABoard. It uses an 18F4550 and a 16F877A (just like the new MC ICD2). Both PICs are programmed with bootloader firmware. Actually, I think the 18F4550 file we have contains an operating system too.

So, it's simply an inexpensive USB ICD2 "Inchworm", of sorts (grin), which is powered from the USB port.

Mike

<added>

I'd still like to hear about your L-C Meter.

I tried building that part, could never get past the USB driver for the 18F4550. Nice ICD, tell me if you get it to work.

As for the LC Meter, Heres the site with the 16F628A code & schematic.
**broken link removed**

And here's a photo of mine.

 

[Jay.slovak]

After reading **broken link removed** I have decided to include Variable Vpp in my new design. ICD2 is not that dumb after all.

I will probably stick to MAX632 + MCP41010 solution.

 

[Mike - K8LH]

After reading **broken link removed** I have decided to include Variable Vpp in my new design. ICD2 is not that dumb after all.

I will probably stick to MAX632 + MCP41010 solution.

That's great Jay. Just remember, no one is exactly sure how the ICD2 firmware controls VPP through that 256-step digital pot.

I may do it the same way you are but only after exploring the possibility of using a single chip to accomplish the same task.

Mike

 

[Mike - K8LH]

I tried building that part, could never get past the USB driver for the 18F4550. Nice ICD, tell me if you get it to work.

I'm still laying it out my version, however there are several guys on EDABoard who have theirs up-n-runnin' already.

As for the LC Meter, Heres the site with the 16F628A code & schematic.
**broken link removed**

And here's a photo of mine.

Looks very nice Bill.

That's the same design I tried but I think I was a little too agressive in my design changes and I have to get back to work on it sometime soon. My design used the serial port and Hyperterminal instead of an LCD and I also eliminated the LM311 comparator (the LC oscillator) in favor of the '628A internal comparator (also used as an LC oscillator). This required using TMR1 for the frequency counter instead of TMR0.

 

[Mike - K8LH]

I'm just getting ready to start experimenting with the 12F683 boost regulator design after studying the Inductor formulas in a spreadsheet. I suspect I might be able to get away with the little radial 220uh/130ma inductor for variable 10v to 13v output at 25-ma. What do you Gentlemen think?

Bill was right. You need A2D feedback for a "pulse skipping" boost design.

Any comments/suggestions/criticism welcome. Regards, Mike

 

[William At MyBlueRoom]

Question, which is better; do you "skip pulses" or vary the duty cycle?

 

[Mike - K8LH]

Question, which is better; do you "skip pulses" or vary the duty cycle?

At this early point, I have no idea (grin) but it'll be fun to experiment with the values.

Mike

 

[Mike - K8LH]

One of the guys on EDABoard just passed along this link to a reasonably comprehensive Boost Calculator which is helping me figure out the relationships. Pretty cool.

**broken link removed**

 

[mramos1]

I'm still laying it out my version, however there are several guys on EDABoard who have theirs up-n-runnin' already.

That's the same design I tried but I think I was a little too agressive in my design changes and I have to get back to work on it sometime soon. My design used the serial port and Hyperterminal instead of an LCD and I also eliminated the LM311 comparator (the LC oscillator) in favor of the '628A internal comparator (also used as an LC oscillator). This required using TMR1 for the frequency counter instead of TMR0.

Is this a working unit? Any .HEX file for it. I have some 628A I ordered and have not opened yet. And a good LC meter I need for sure.. I can hook to an old 386 laptop with a serial port. Is the TTL RS232 inverted?

 

[Mike - K8LH]

Single Chip L-C Meter ?

I need to dig out the circuit board and work on it again soon. The code was not complete but I did have the comparator setup correctly and it was oscillating around 500-KHz. The frequency counter on TMR1 was working too but I was disturbed by the amount of oscillator frequency drift and I was wondering if it was because I was using 1/8th watt resistors and had everything crammed into a very small space.

When I figure it all out I'll publish it in the Projects forum for everyone to enjoy.

Meanwhile, that dual-chip (628A/LM311) design is proven and tested so you might want to check that out.

Mike

 

[mramos1]

I do not have the LM331, I thought if it was done and I had the 628a sitting here.. Will wait, my meters (I have like 8 of them) work. I have my favorite ones for tasks, like C and uA, mV.. They are close enough for now..

Think I will go drill the ICD2 inchworm board. Bits never showed, but I can use the old dull one.

Thanks for the feedback. I have a ATMEL 1200A curcuit I guy wants me to drop from 1Mhz (INT OSC) to 32.7Khz.. Maybe I will work on that. Lots of timing loops in it.. Nigel had to tell me how to get things to run longer on battery. Now I am redoing stuff.. But it is cool, running on battery is not a bad thing. The pic takes the 32Khz xtals well, lets see how Atmel does, but they have always been rock solid for me.