PIC programmer via PIC18F4455

[Vizier87]

Hi guys,

1. Usually the DIY-ers who built their own USB PIC programmers use the ubiquitous 18F2550. However, since PIC18F4455/4550 are also enables USB connections, are there documentations on how to use a PIC18F4455/4550 to do the same thing? I have a 4455 main board already, and I don't wan't to spend too much time building a new one, rather I'd just mount another circuit on the main board for the ICSP function.

2. I was rather thinking of a circuit purely based on resistors/caps just to load programs. Simply put, a USB>>PIC>>ICSP terminals kinda thing.

For instance, I got this schematic:
**broken link removed**

and I wondered if omitting the MOSFETs would still render the programmer functioning?

Thanks
Vizier87.

 

[Wp100]

Hi,

Would suggest you use Bills BlueRoom Pickit2 Lite design - it works !

 

[Vizier87]

Wp100 you rock!!! thanks for the schematic, I'll be constructing it ASAP. It's PICkit 2 compliant, isn't it? Also can I have the link to the bootloader hex files?

 

[Wp100]

Hi,

Yes, you burn the chip with the free Microchip Pickit2 v2.32 software found here **broken link removed**
The program also burns straight in to a 4550 chip, have done it myself.

You do not actually need the ferrite on the usb line, but use it if you have one.
The little choke is shown as 680uh but have found it still works ok with 470uh.
Just ensure you get the correct pin out for the transistors you buy.
Also ensure D2 is a schottky type otherwise the voltage drop is too great.

As wel as all standard Pk2 programming and debugging functions you can also use the Usart tool and the logic analyzer tool.

Though set for 5v only, you can program a 3.3 v chip by powering the whole PK2 circuit with 3v3.

 

[Vizier87]

The program also burns straight in to a 4550 chip, have done it myself.

Hi,
I assume the passive components should be assigned to the 4550 pins according to the same designations on the 2550. Is that correct?
Thanks.

 

[Wp100]

Hi,

Yes , its easy to mix them up by mistake, particulary the VUSB, D+ and D- pins

On the circiut diagram I would remove all the Pin numbers 1 - 28 then write in all the 4550 pin numbers all at the same time.


Have you see this link about using the PK2 to program the Megas, not tried it with the Pk2Lite, it would need the Aux connection to Pin6 making, would a simple wire and resistor do ? - not sure if it needs other parts to control it or not.
http://pickit2.isgreat.org/

If you download Pickit2 V2.61 stand alone program it contains the Pk2 user Guide which includes the full circuit diagram, plus details of how to configure your targets board for ICSP and Debugger.

Note that V2.61 is a totally separate programmer utility to the MPLAB PK2 programmer and debugger.

 

[Vizier87]

Alright Dr Wp100, I'll take note all of that. Thanks a lot man.

 

[Vizier87]

Hi, I noticed that Q1 doesn't have a real load for itself therefore it'll directly turn on, dissipating power. I found out that it heats up uncontrollably. Is it supposed to be like that? The red LED also turned on. I wonder if there could be anything else which I should take note here? The Inductor is not 470uH, so I settled down for a 330uH (or I think it is, since it has two orange stripes and a gold stripe), is that the main cause?
**broken link removed**

 

[Wp100]

Hi,

The circuit is a very well proven design so it must be a fault in your construction.

For a part to heat up like you describe is clearly wrong, that part should be replaced after the fault found.

Common problems apart from obvious wiring /soldering errors are the incorrect pin outs of the transistors.
The Inductor should be 680uh, I found 470 did work but no idea if 330uh works properly.

 

[Vizier87]

yeah, I built mine on a donut board. It looked pretty neat but I suspect it has some misconnections somewhere. I guess I just have to rebuild it on a PCB now.

Anyway, thanks. I'll take into account the rest of the advice.

Vizier87.

 

[Wp100]

Vizier87
so I settled down for a 330uH (or I think it is, since it has two orange stripes and a gold stripe),

Not 100% sure of inductor colour coding, but my 470uh is Yellow,Violet,Brown then Gold which kind of implies yours may be just 33uh ..?

Perhaps search this forum for Pickit2 Lite / Bill at Blueroom Electronics to see if there is any comment about the value / range needed to give the required voltage.