Programmer

[GatorGuy]

I have found this PIC programmer in several places and was wondering if this would still work for the 16F627?

 

[williB]

i've never seen a 78L05 being powered by the serial port..but thats just me..
to answer your question it would depend on the programmer software
since both the F84 & the F627 are 14 bit cores it should work..

 

[upand_at_them]

No, it won't work.

TXD is supplying the power, which means it will get switched on and off. The 16F627 needs MCLR to be held high without interruption. Don't try gimmicky stuff. If you want a programmer powered by the serial port then get an Olimex PG-1 or PG-2.

Mike

 

[GatorGuy]

What if you added a power circuit to the schematic and took it off of the TXD? If that would fix it could it also be used to program other 14 bit PICS?

 

[Nigel Goodwin]

No, it won't work.

I wouldn't go as far as that! - it's basically another varient on the JDM type programmer, presumably it comes with the required software?, and does that support the 627/628?.

However, generally the 'serial' port programmers like this have a reputation for poor reliability, parallel port programmers are generally more reliable - or a proper serial port programmer, which has an onboard processor.

 

[upand_at_them]

Dude, this has already been worked out. It's called a JDM programmer. Olimex makes then and various places on the web sell them.

Mike

 

[Jay.slovak]

However, generally the 'serial' port programmers like this have a reputation for poor reliability, parallel port programmers are generally more reliable - or a proper serial port programmer, which has an onboard processor.

Nigel, do you have personal experience with JDM (or other serial) based programmers? I just want to know, because everybody says that, but I don't know anybody who had such problems... 8)

 

[Nigel Goodwin]

However, generally the 'serial' port programmers like this have a reputation for poor reliability, parallel port programmers are generally more reliable - or a proper serial port programmer, which has an onboard processor.

Nigel, do you have personal experience with JDM (or other serial) based programmers? I just want to know, because everybody says that, but I don't know anybody who had such problems... 8)

Not personally, but I've had MANY emails from people who have had problems - the author of ICProg doesn't offer any support (presumably because ICProg supports the JDM?) - so people email ME? instead.

I don't see how it can be very reliable?, even the guy who designed it says it's not - as I've always seen it, it's a very clever piece of design (which is quite obscure in operation!), but designed more as a design exercise in parts reduction than as a practical programmer.

As someone who's been involved in PIC programmers since before Microsoft Windows, I've seen a lot of different types, and a simple look at that circuit shows you could have problems. Serial ports vary greatly on their output voltages, and the original JDM requires it to exceed the RS232 specification. Some of the later designs are better, but can still fail on a port which is still within the RS232 spec.

 

[Jay.slovak]

However, generally the 'serial' port programmers like this have a reputation for poor reliability, parallel port programmers are generally more reliable - or a proper serial port programmer, which has an onboard processor.

Nigel, do you have personal experience with JDM (or other serial) based programmers? I just want to know, because everybody says that, but I don't know anybody who had such problems... 8)

Not personally, but I've had MANY emails from people who have had problems - the author of ICProg doesn't offer any support (presumably because ICProg supports the JDM?) - so people email ME? instead.

I don't see how it can be very reliable?, even the guy who designed it says it's not - as I've always seen it, it's a very clever piece of design (which is quite obscure in operation!), but designed more as a design exercise in parts reduction than as a practical programmer.

As someone who's been involved in PIC programmers since before Microsoft Windows, I've seen a lot of different types, and a simple look at that circuit shows you could have problems. Serial ports vary greatly on their output voltages, and the original JDM requires it to exceed the RS232 specification. Some of the later designs are better, but can still fail on a port which is still within the RS232 spec.

I knew about JDM's vulnerabilty, I just wanted to know if you used it.... cool :lol:

 

[upand_at_them]

I've used the JDM and it usually works. I do run into problems every now and then when it just won't work; I think it's OS related, because I never had problems when I was running Win98.

Mike

 

[KMD]

I bought a JDM programmer, it worked ok for about 2 or 3 days using icprog, then it just stopped. Nothing on the PC or software changed, it just wouldn't program anymore. I would advise anyone getting started on these to just spend the extra cash on an externally powered programmer, it made my life a lot better.

 

[Jay.slovak]

I bought a JDM programmer, it worked ok for about 2 or 3 days using icprog, then it just stopped. Nothing on the PC or software changed, it just wouldn't program anymore. I would advise anyone getting started on these to just spend the extra cash on an externally powered programmer, it made my life a lot better.

You Actually bought it? I made it like for 1$... and I didn't regret that, served my well.

 

[KMD]

Yea, I'm kind of lazy sometimes. . Actually, I'm such a newbie at all this electronics stuff, including uC, I didn't want to spend an hour building one and then 10+ hours trying to figure out why mine didn't work. So instead, I spent $10 and 20+ hours trying to figure out why the one I bought just stopped working all of a sudden. On the plus side, I leaned allot about serial ports, JDM programmers, how all programmers work in general, and a bit more about general electronics.

 

[Jay.slovak]

Yea, I'm kind of lazy sometimes. . Actually, I'm such a newbie at all this electronics stuff, including uC, I didn't want to spend an hour building one and then 10+ hours trying to figure out why mine didn't work. So instead, I spent $10 and 20+ hours trying to figure out why the one I bought just stopped working all of a sudden. On the plus side, I leaned allot about serial ports, JDM programmers, how all programmers work in general, and a bit more about general electronics.

I prefer to learn on others misstakes, that's much cheaper :twisted:

 

[GatorGuy]

Okay I have made a quick schematic of Lothar Stolz's LVP JDM programmer. Could some one take a look at it and tell me what you think? I am thinking about using this for the 16F627/16F627A. Please forgive me if something is off. I am doing my best at learning. Everyone on here has been a big help!

-C

 

[Jay.slovak]

Okay I have made a quick schematic of Lothar Stolz's LVP JDM programmer. Could some one take a look at it and tell me what you think? I am thinking about using this for the 16F627/16F627A. Please forgive me if something is off. I am doing my best at learning. Everyone on here has been a big help!

-C

Well, I would definitelly add 2x 100nF capacitors + 100uF capacitor to filter the input volatge.

Also I have to say that this "scheme" is not very carefull to the PICs (it is using internal diodes to limit the voltage and RS-232 limiting resistors)...

 

[GatorGuy]

Well, I would definitelly add 2x 100nF capacitors + 100uF capacitor to filter the input volatge.

Adding the Caps. :wink:

Also I have to say that this "scheme" is not very carefull to the PICs (it is using internal diodes to limit the voltage and RS-232 limiting resistors)...

How would you change the power supply to be "safer"?

 

[Jay.slovak]

Also I have to say that this "scheme" is not very carefull to the PICs (it is using internal diodes to limit the voltage and RS-232 limiting resistors)...

How would you change the power supply to be "safer"?

The Power supply is not the problem! But the way the PIC is connected with serial Port is not good. Because RS-232s voltage levels of +-12V :? are "Clamped down" to 0-5V using PIC's internal diodes...
I would definitelly use JDM design instead...

 

[GatorGuy]

Another quick question. The schematic has the ground from the power supply hooked up to Vss. Which is also connected to pin 5 on the serial port. If the 78L05's com is on the same ground could it hurt the serial port at all?

 

[GatorGuy]

The Power supply is not the problem! But the way the PIC is connected with serial Port is not good. Because RS-232s voltage levels of +-12V :? are "Clamped down" to 0-5V using PIC's internal diodes...
I would definitelly use JDM design instead...

I'm sorry, that is what I meant. But wouldn't the resistors bring the voltage down before entering the PIC?