Need some help with programmer

[wmmullaney]

Sorry to keep on asking silly Q's, Im really new to this and know hardly anything. Today I got my PIC16f628a in the mail, and I wanted to start programming, but I was confused by (on the programmer) which direction the PIC's notch go?(toward the ICSP plug or the other way)

Does this programmer(JDM) use HVP or LVP?

Does it need 12v to operate correctly?

 

[mvs sarma]

indicate the make and model or a schematic of the Programmer-- JDM)-- no point in just telling JDM-- indicate 18 pin zif or 40 pin zif- and if 40 pin how is it wired?
If you try to use LVP facility, perhaps you loose one pin for real use and your programm should not use that pin.
the pin counting is very standard and instead of asking a querry which you feel is silly, perhaps you may see the datasheet for PIC16F628A and everything becomes clear as you start studying that

however google for JDM or JDM B for the schematics.

 

[eblc1388]

Does this programmer(JDM) use HVP or LVP?

Most definitely HVP. I have yet to see one using only LVP.

Does it need 12v to operate correctly?

Oh, definitely yes.

However, the original JDM design tries to derive the required +12V and +5V from the Serial port pin signals. This method usually works for older desktop PC because their serial port signal match that required by the RS232 specification closely. The old driver ICs inside the PC are powered by +/-12V. (The MC1488 and MC1489...etc...)

With modern PC and laptop, the signals level are somewhat reduced for whatever reasons and therefore in some cases the JDM circuit can no longer produce the required +12V to program a PIC correctly.

Many people attribute this to the fault of the JDM design but this is a bit unfair as it works correctly before.

 

[Nigel Goodwin]

Many people attribute this to the fault of the JDM design but this is a bit unfair as it works correctly before.

Considering the author of the JDM admitted this back when it first appeared, it's obviously the fault of the design - and he never pretended it wasn't.

The JDM was purely a (very clever) design to use the absolute minimum of components - reliability and repeatability were never really concerns. It also relied on the serial port actually exceeding the RS232 spec, which many old machines did.

It's unfortunate really, the low reliability of the JDM has probably put more people off PIC's than anything else?

 

[mvs sarma]

Considering the author of the JDM admitted this back when it first appeared, it's obviously the fault of the design - and he never pretended it wasn't.

The JDM was purely a (very clever) design to use the absolute minimum of components - reliability and repeatability were never really concerns. It also relied on the serial port actually exceeding the RS232 spec, which many old machines did.

It's unfortunate really, the low reliability of the JDM has probably put more people off PIC's than anything else?

i feel that the JDM may not give the load currents to the extent of USB or external power.
if the modern PCs are not able to give Vpp directly, due to modernized circuitry, at least they can give 5V with reasonable load. now I would suggest to use a dc-dc converter chip for deriving 12.5 or say 13V . There is not much load on this. Thus, we may perhaps try to see this as a concept instead of depending on the uncertain Vpp from a conventional JDM. agreed that there is nothing to think to put external power supply. I do understand that the original design was meant for those times with chips like 1488 or 1489 in the PC.

New laptops don't even have COM ports. they only have usb.
Perhaps the best is to go for USB based witha cheaper support PIC in 18F series. and use the 5V.
for old versions, the best appears to steal power from usb and use the com port only for signals,. the Vpp may have to be generated inside the programmer by Dc-DC conversion as discussed earlier.

 

[wmmullaney]

Sorry, I think I figured it out, anyway this is the page. My old desktop's srial port is 11.5v, is that enough?

https://www.sparkfun.com/commerce/product_info.php?products_id=8

 

[mvs sarma]

Sorry, I think I figured it out, anyway this is the page. My old desktop's srial port is 11.5v, is that enough?

https://www.sparkfun.com/commerce/product_info.php?products_id=8

replace C1 to 47uF/25V if you have, the LED has to be RED color-- then measure the voltage across C1 it will be 1.4+6.2+5.1=12.9 approximately.
the voltage across the other cap should be 5.1 v.
check and let us see.

IMPORTANT: ensure that the COM port cable is shortest at say less than 18 inches. the supplier gave you 6 feet (too bad for our purpose), if i get the data from the site.
I don't know how, but have a shorter one.

for driver try using winpic800

 

[wmmullaney]

Thanks, I don't really want to mod my programmer, I'd mess something up, I just want some way to program it with the hardware I have. What will it do if I tried to program now?

 

[Nigel Goodwin]

Thanks, I don't really want to mod my programmer, I'd mess something up, I just want some way to program it with the hardware I have. What will it do if I tried to program now?

It will either work, or it won't.

 

[blueroomelectronics]

PICs are pretty robust, a RS232 port is only capable of a few ma so just hook it up and give it a try.

 

[skyhawk]

My old desktop's serial port is 11.5v, is that enough?

According to the programming specifications for 16F627A/628A/648A
10.0< Vpp<13.5, so it should be fine.

https://www.electro-tech-online.com/custompdfs/2008/01/41196g.pdf

One combination of options to avoid with the JDM programmer is internal oscillator and RA5 as I/O. You may not be able to reprogram because the JDM programmer can't do VPP before VDD.

 

[Hero999]

Some PIC must require 13V or the PIC programmer which I built wouldn't have a 13V supply, it'd just use a standard 12V supply.

 

[Nigel Goodwin]

Some PIC must require 13V or the PIC programmer which I built wouldn't have a 13V supply, it'd just use a standard 12V supply.

A lot of PIC's require 12V on Vpp to switch to programming mode, not 11.9V, it must be at least 12V - by using a 13V supply you are guaranteed more than 12V even after the Vpp switch transistor.

Because of problems on the very early programmers, many of which had adjustable Vpp for that reason, 13V became the standard amongst hobbiest programmers.

This is why the JDM programmers give the 'verify error at 0x000', because they don't provide enough Vpp voltage.

 

[Funny NYPD]

voltage is one requirement from the new chips, power sequence between vpp and vdd is another "new" requirement.