PIC18F2550-I/SP programming issues

[The_JinJ]

Are you using a aready made cable to connect the MegaDrum to the computer COM port? . if you are be aware that their Are two typesof cable one with Straight Connection and one with Crossover Connections.
This site explains it
http://digital.ni.com/public.nsf/allkb/ ... 720071DECF

No, using a DIY one.....

[The_JinJ]

At a loss now

Checked for shorts....changed components....rebuilt cable....changed computer....new PIC....

Still fails to write to PIC

ANY other ideas? HELP!

[jman 31]

Have you powered it up to see if it works? Mine said failed to write, but it worked. I have no idea why except maybe a glitch in the program.

[The_JinJ]

Have you powered it up to see if it works? Mine said failed to write, but it worked. I have no idea why except maybe a glitch in the program.

XP doesn't detect it - nothing appears to be written, when read it reads all 00ffff so def appears to not have written anything.

[jman 31]

If you are in the states and you want to send it to me, I can program it for you. No charge or anything. Just pay shipping both ways.

[The_JinJ]

If you are in the states and you want to send it to me, I can program it for you. No charge or anything. Just pay shipping both ways.

Thanks for that but in the UK - I may use a breadboard to program to isolate from the rest of the circuit.

[oliboy]

had the same problem as yours...changed the board three times and even bought 2 new pics with no success of programming...what i did is programmed it using a different programmer and WALLA!!it worked when i connected it to the board and magically the 3.3V at pic 14 just appeared...WEIRD!!

[The_JinJ]

Quick question, using ICSP should VPP (pin1) voltage increase to enter into programming mode? Sits at steady 5v

Edit, seems I've answered my own question

25.10
Single-Supply ICSP Programming
The LVP configuration bit enables Single-Supply ICSP
Programming (formerly known as Low-Voltage ICSP
Programming or LVP). When Single-Supply Program-
ming is enabled, the microcontroller can be
programmed without requiring high voltage being
applied to the MCLR/VPP/RE3 pin, but the
RB5/KBI1/PGM pin is then dedicated to controlling
Program mode entry and is not available as a general
purpose I/O pin.
While programming using Single-Supply Program-
ming, VDD is applied to the MCLR/VPP/RE3 pin as in
normal execution mode. To enter Programming mode,
VDD is applied to the PGM pin.

When i read the chip LVP is disabled - can it only be enabled with a programmer using high voltage on pin 1 VPP?

Once LVP has been disabled,
only the standard high-voltage programming is
available and must be used to program the device.

[Firelord]

ANY other ideas? HELP!

Try changing COM port baud rate.

[The_JinJ]

ANY other ideas? HELP!

Try changing COM port baud rate.

No joy

Now have the PIC on a breadboard and trying that way so removes Megadrum circuit problems. Trying with non LVP to program but the voltage doesn't rise above 5v on Pin 1 - is this a comm port issue?

Wired like this:

Pin 1 --> 10k resistor --> Pin 20 VDD
Pin 20 --> 5V
Pin 19 --> GND --> DB9 Pin 5
Pin 26--> 10k --> DB9 Pin 3
Pin 27 --> 10k --> DB9 Pin 7
Pin 28 --> 10k --> DB9 Pin 4
Pin 28 --> DB9 Pin 8

+5v and GND from USB