LAB-XUSB Experimenter Board help

[aerostar]

This
cfg = _XT_OSC ; XT oscillator

Should be
cfg = _HS_OSC

Check this syntax

[ERMEGM]

Well, changing the config did it, but only for the LCD sample program where it just repeats saying Hello World. On this key press program, I am getting mixed results. Sometimes it's a single line of blocks. Other times it's a cursor or 9 characters like arrow symbols and slashes. When I press a button, each one yields a ?. If I hit the reset button, those characters side step off of the lcd.

At one point, when I played with the power up and watchdog timers, I did get the words "press any key" however, several of the letters were missing.

The schematic of the board is available at the links provided. Nothing was changed, or requires to be changed on the jumpers. I have JP2 set to USB power instead of a wall wart.

The chip I have matches the pinout of the 4550 exactly, so the configuration should be the same. I thought buying the completed board and using the sample programs was going to be straight forward. Silly me.

[Scampy]

Well, changing the config did it, but only for the LCD sample program where it just repeats saying Hello World.

this is confusing - from what I can see the crystal on the board is 20 Mhz, but the OSC value in the first bit of code is 48 !

What happens if you change the OSC to 48 or 40 in your code ? - Also, comment out the section of the code that deals with the key pad and make the main loop a simple LCDout "hello world" - once you get that part running then you know you have the config and LCD setting right, and then you can un-comment the switch routines and debug them.

[towlerg]

this is confusing - from what I can see the crystal on the board is 20 Mhz, but the OSC
value in the first bit of code is 48

check out the fuses, PLL etc. 48Hhz is needed for USB

[ERMEGM]

It IS confusing. As I said, I made the change to the LCD program that just says Hello World over and over again, but it doesn't work on the keypad program.

I'm still learning this type of code, so the error could be right in front of me and I won't see it. That's why I'm asking for help deciphering this type of coding.

Thanks,
Tony

[AvionicsMaster1]

Demon hit on an issue that comes up here repeatedly. Writing define osc 20 doesn't do the job but define OSC 20 will. I use his method and write the whole define statement in caps like DEFINE OSC 20. That needs to be addressed first.

[Tabsoft]

Absolutely.

From the PBP manual in the "DEFINEs Defined" section.
For the practical PBP user, there are a couple of fundamental points to consider:
1) DEFINEs are CASE SENSITIVE!

All PBP DEFINE parameters are UPPERCASE.

So when you use "osc"' "Osc" "oSc" "osC" "OSc" "oSC" "OsC", PBP will not recognize these as OSC defines and will use the default OSC setting.

ONLY "OSC" will actually tell PBP you are setting the OSC speed.

The correct statement for your program is:
"DEFINE OSC 20"

The Microcode Studio UI will change the "DEFINE" keyword to lower case when it is displayed I.e. "define" but that is only what is displayed in the UI. It does not actually change the text in the file to lowercase. More importantly it does not change the "OSC" parameter. It will leave it as you typed it.

[Scampy]

check out the fuses, PLL etc. 48Hhz is needed for USB

But how would you get the timing right with a 20mhz crystal. I thought HS setting means that you run at the crystal speed, and the HS_PLL is typically a multiplier (of 4). IE to get 48 Mhz a 12 Mhz crystal is required, OSC is set to 48 and the fuse set to HS_PLL. - From the pictures of this LAB it's not clear if you can interchange the crystals, which is why I found that confusing.

[Tabsoft]

Malc,

ERMEGM is not using a 18F4550 in the board. He is using a 16F874A.
It's max rate is 20MHz using HS mode.

The 18F4550 is a bit of a different animal as far as I can tell looking at the DS.

It can take a 20MHz input in HSPLL mode that then gets divided by 5 to drive a 4MHz input into the PLL to get a 96MHz PLL clock. You can then select to divided down to 48MHz for the MCU clock. This allows the USB and MCU to run from a common source but at different rates.

[Scampy]

Malc,

ERMEGM is not using a 18F4550 in the board. He is using a 16F874A.
It's max rate is 20MHz using HS mode.

The 18F4550 is a bit of a different animal as far as I can tell looking at the DS.

It can take a 20MHz input in HSPLL mode that then gets divided by 5 to drive a 4MHz input into the PLL to get a 96MHz PLL clock. You can then select to divided down to 48MHz for the MCU clock. This allows the USB and MCU to run from a common source but at different rates.

Thanks for the explanation... learning something new every day