18F452 to SL811HS interfacing

Please post a schematic.

Let's just say that is it. After the original post I received an e-mail alerting me to the project. It was nearly identical to mine, so I rearranged a few IO lines to make it compatible (except the uC on mine runs at 8MHz). Then I changed a few "#define"s in my source to match. Amazingly enough my alterations didn't change anything for better or worse.

Going from a feeling, it's like either D0 is stuck high, or the nWR line isn't working. I can't find a sign of either being the case though.

Given that the value it regurgitates isn't changed even if I write a value to an address and read it back immediately the problem is a little hard to pin down.

So, you removed the '245 from your circuit ???

I never had one. I was asking if I should put one in. Sorry that my post lacked clarity. At any rate, last night I went through and checked again for open circuits and shorts. Couldn't find anything.

Lets start over.

Is your circuit the same as the one on the schematic on:

Is the timing of your circuit the same as:

Is your code is C or assembly ?

Do you have a scope ?

Do you have an LED and a 1K resistor ?

Have you written a monitor program to read and write I/O ports ?

Do you know for sure that the I/O ports are working ??

When you set port B for input, can you tell that each bit is working ?

When you set port B for output, can you tell that each bit is working ?

Take this in small steps.

If you don't have a scope, then an LED will work as well, just slower.

Good Luck

donald

Close enough. The differences are as follows:

• I have larger power filter caps

• The clock for the uC is derived from an external 7.881988MHz clock.

• I don't have the LEDs or the pushbuttons.

• There is a piezo for debugging feedback on otherwise unused pins.

• My 3.3v rail regulator is different (but correct and tested).

Yes.

C. Using CCSC. It's more or less a port of the MicroUSB code (6502 asm).

Unfortunately not.

In abundance.

Only to read and write preset values via my IO functions to the 811HS. Good idea. I'll make a generic one for testing all pins.

The RS232 and the piezo function. I believe the /RESET line works also because resetting the SL811HS then gives a false reading of having a USB device detected, indicating the line is working.

Port B? Haven't tried. Will check. Same for output.

thankyou for your help. I'll go over it a bit later. In the meantime, I'll knock up a monitor.

Something to note is that earlier on in the project it was more sane. This was before I picked up on a few truly bizarre fabrication mistakes. Since then I've even replaced the SL811HS to be sure I didn't kill it. Even though my mistakes probably wouldn't have. Most notably one of the grounds of the 811HS going via a resistor. I hate to think how that happened.

thanks, I need it.

Tristan.

Opps, sorry its port D.

I hope you are not using port D as a PSP (Parallel Slave Port).

The PIC chips can _not_ input or output from this port programmaticly. Its only used by an _external_ device to access a configured PSP.

Not in PSP mode. Checked that a couple of times. Been writing the monitor. Ran into one silly hitch. input(pin) only accepts constant pin numbers. CCSC is good for some things but a pain for others.

I know it's a self-reply. Just thought I'd say I've gone over it and the source of the problem eludes me. Well, I know the source. It's sitting in front of the PC right now. I'm going to start from scratch with a different board layout (Still flying lead style) with the '811HS on its own small daughterboard with support circuitry. That way it's easier to debug and reuse for other experimental projects.

I know there are better ways to do it but it's mostly for educational and experimental purposes anyway.

Thankyou for your help. Unfortunately I can't really nail the problem with my current equipment, so it's easier just to start again. It gives me an opportunity to make some more additions anyway.