ICD2 Compatable + PCB layout

[William At MyBlueRoom]

Bill,

Sorry if I'm goin' off-topic again but I thought you might be interested in a neat layout I just stumbled upon for a USB-ICD2 clone from a chap in Hong Kong. It really looks like a decent layout for through-hole components and it includes the 74HCT125 buffers which will allow 3.3v target operation for dsPIC and PIC24 devices. I may change my USB-ICD2 layout to look a little more like this one.

BTW, I emailed this chap to ask if he'd sell me blank printed circuit boards and I'll let you know what he says.

Mike

It's a beautiful looking board, what's the cost I wonder. I have a Hong Kong connection if you need to contact him. I assume that's a 18F4550 on the left.

What USB driver did you use with the 18F4550? I tried the Microchip driver but no go.

PS he's got a 16MHz xtal on the left IC, most use either 20 or 24 MHz for USB. And what's the multiturn pot for?

PPS I've left the error LED off my design, never seen it lit. What sort of errors is it for?

 

[William At MyBlueRoom]

Yea, I will drill, I was just all of a sudden in a hurry to have one.. But will start tonight. I have new bits in the mail today as well, mine is dull.



They have a USB unit for $23 or $29. But no ICD. Yea, they just dropped the wallwart. I have 4 on my bench, so that is not a bad thing for me.

I will drill tonight and try to get it finished, then start getting parts. I get that far. I will order the PICs There are a lot of wholes I can skip and but the pins on the socket. That will help.

And let me know what the fellow says on the USB-ICD2 clone for sure.

Lots of the 40 pin 16F877 holes aren't used, don't drill just cut the socket leads

 

[Mike - K8LH]

It's a beautiful looking board, what's the cost I wonder. I have a Hong Kong connection if you need to contact him. I assume that's a 18F4550 on the left.

Yes, that'll be an 18F4550 on the left.

What USB driver did you use with the 18F4550? I tried the Microchip driver but no go.

I've got an 'image' of the ICD2 '4550 bootloader + OS from the chaps on EDABoard.

PS he's got a 16MHz xtal on the left IC, most use either 20 or 24 MHz for USB. And what's the multiturn pot for?

The 20-MHz xtal is used for both the '4550 and the '877A. That 16-MHz xtal and trim pot is probably being used for the little 8-pin VPP chip at bottom left (I'm guessing).

PPS I've left the error LED off my design, never seen it lit. What sort of errors is it for?

I don't know. I left it off my Serial ICD2 too since the ICD2 tab in MPLAB always tells you when there's an error.

I'm trying to see how small I can make my USB-ICD2 board. This (below) is just a test layout and that's why it looks like crap. All ground connections are on the hidden top ground plane layer. I'm using the USB LED as a power LED (it seemed redundant to have both). I still need to hook up a few transistors, a VPP generator of some sort, and an ISP connector.

The picture is of one chaps USB clone (on EDABoard) and I have the complete project file, single sided PCB artwork, and hex files if you need them.

 

[William At MyBlueRoom]

Yes Mike please post or email all the files for the new USB version.

 

[mramos1]

Post would be nice.

Did not get to drilling the board, wound up doing a Windows GUI project that ran longer than planned.

 

[Mike - K8LH]

Hi Guys,

Here's the files for user PiCS's through-hole USB ICD2 project including schematic/pcb file (pdf) and the two hex files.

Mike

 

[jcdup]

William,

Thanks for the Inchworm details. I built it on strip board-- too lazy to make a pcb.

Initially Mplab lost connection with it often and lots of operations failed. To test the hardware I loaded the PIC (16F877) with a LED blinking program which did not run. However, sometimes when I touched the board or a component it would run. Initially I thought the oscillator was not running but it turns out that MCLR was not held high. After adding a 10K resistor between MCLR (pin 1) and +5V Mplab now connects and I succeeded in downloading the OS to my Inchworm.

I'm not sure whether it is the Inchworm design, or simply a peculiarity of my board, but I thought this might help someone else.

Thanks again

Johann

 

[William At MyBlueRoom]

After adding a 10K resistor between MCLR (pin 1) and +5V Mplab now connects and I succeeded in downloading the OS to my Inchworm.

I'm not sure whether it is the Inchworm design, or simply a peculiarity of my board, but I thought this might help someone else.

Thanks again

Johann

Glad to hear you got it running, it's a great tool and decent programmer. I've noticed that too that some serial ports may not pull DTR (rs232 pin 4) high. The inchworm is based on the many common ICD2 designs on the web, and I've not seen any with the pullup. Many use a single 5.1V zener for D8 and omit D7. I avoided all zeners in the inchworm, for some people they're hard to find.

I'm working on an assembly manual for the retailer that wants to carry it. I'll make a note about adding a 10K pullup as it should hurt the design.

I originally wanted to add a JDR bootloader to the design. So you could program the 16F877 bootloader in the inchworm then switch off the JDR mode. Although in such a modest design I wanted to keep the costs very low.

Maybe for the next inchworm 2...

Did you handwire or make a pcb?

 

[Mike - K8LH]

I used the zener on my serial clone and have not experienced that problem (having only used it on 6 or 7 different computers).

 

[jcdup]

Did you handwire or make a pcb?

I did not create a pcb, but built it on strip board (vero board?).

Thanks again.


Johann

 

[Nigel Goodwin]

I did not create a pcb, but built it on strip board (vero board?).

Do you have a picture of it?.

 

[jcdup]

Do you have a picture of it?.

Successfully programmed and debugged a PIC16F819 last night. I got a few framing errors on verification but I think it is my serial cable as it succeeded if I retried.

I stilll have to add a connector for the power supply and cut the lid for the target connector.

Cheers

Johann

 

[William At MyBlueRoom]

That's awesome jcdup. Nice work. Try removing unsoldering 1 lead of the the 10K mclr resistor you added, it should still work with mplab (not sure if it's loading the DTR line)

 

[mramos1]

FYI: Drilled the inchworm PCB last night. Will start stuffing it tonight. I need to get an 877 on the way..

Has a couple little drill slips getting back into it. But all can be fixed.

 

[Mike - K8LH]

This from MPLAB ICD2 Release Notes in my MPLAB 7.40 installation;

6.1 MPLAB ICD 2 Power

Serial (RS-232) connection to the PC:
Power supply required.

USB connection to the PC, target not powered from MPLAB ICD 2 or no target connected:
No power supply needed.

USB connection to the PC, target powered from MPLAB ICD 2:
Power supply required. (USB cannot power both.)

Note: Plug in USB first, then power supply.
The MPLAB ICD 2 cannot be powered from the target board.

6.2 Target Board Power

The MPLAB ICD 2 can provide 5 V and up to 200 mA to a target if the ICD itself is powered by a power supply. (USB cannot power both.) This is enabled by checking "Power target circuit from MPLAB ICD 2" (Debugger>Settings, Power tab).

Note: Plug in USB first, then power supply.

They dissallow powering the ICD2 from the Target board. Not sure if that's important or not.

I think a Target VDD switch (2N3906, 2N4403, 2N2907A, etc.) may be important to have in your design (if it isn't too late). I used a P-channel MOSFET on my clone.

Mike

 

[Mike - K8LH]

Mramos1,

Bravo. Glad to hear you're makin' progress. Email me. I can probably post you an '877A tomorrow with the bootloader installed, as well as the other few silly one-off parts you might be missing to complete that puppy.

Mike

 

[jcdup]

That's awesome jcdup. Nice work. Try removing unsoldering 1 lead of the the 10K mclr resistor you added, it should still work with mplab (not sure if it's loading the DTR line)

Thanks William. I will revisit that pull-up register on MCLR, but for now I'm just happy that it works

Cheers

Johann

 

[jcdup]

I think a Target VDD switch (2N3906, 2N4403, 2N2907A, etc.) may be important to have in your design (if it isn't too late). I used a P-channel MOSFET on my clone.

Mike

Thanks Mike for the VDD switch shematics. It should be easy to add this to my strip board. It looks like RA4 is active low. I could also add an LED to this to then indicate whether power is being provided to the target or not.

Once this one's done I'm planning to build the USB ICD2 clone as described on edaboard.com.

Cheers

Johann

 

[mramos1]

Mramos1,

Bravo. Glad to hear you're makin' progress. Email me. I can probably post you an '877A tomorrow with the bootloader installed, as well as the other few silly one-off parts you might be missing to complete that puppy.

Mike

Thanks Mike,

I will pull the schematic today and start a parts list. See if there are parts I might have missed.. Will shoot an EMAIL..

 

[Mike - K8LH]

Thanks Mike for the VDD switch shematics. It should be easy to add this to my strip board. It looks like RA4 is active low. I could also add an LED to this to then indicate whether power is being provided to the target or not.

Once this one's done I'm planning to build the USB ICD2 clone as described on edaboard.com.

Cheers

Johann

You're very welcome Johann.

You're correct, RA4 is active low.

Please note that you should probably move the top of resistor R3 (4K7) over to the Target VDD pin on the ICSP connector if you install the Target VDD switching circuitry. This way the Target VDD ADC will truly be reading Target VDD wether it's being supplied from the Target board or the ICD2.

Good luck on your upcoming USB-ICD2.

Take care. Have fun. Regards, Mike