SX28 with 50m resonator not working

T Chap

Using the Blitz, the SX programs no problem. The program runs using the following:

OSC4mhz Turbo
4_000_000

But when I program it with OSCHS1 Turbo and 50_000_000 the program will not run after downloading the program sucessfully to the SX. The resonator is at the pins with no caps.

Any ideas on whats going on?

Post Edited (originator99) : 9/5/2006 6:08:47 AM GMT

Bean

Try OSCHS2 and/or add BOR42 to the device line.

Bean.

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·

T Chap

Thanks Bean I have tried every setting for the external osc. I added the BOR42, no luck. I have tried a 10k as shown in the manual across osc 1 and 2 as well. I have tried 2 resonators, both from Parallax. I have tried pulling the Blitz after programming, and leaving it in, no difference. The basic circuit is the resonator to th eosx pins and the center pin on the resonator to GND. There's got to be something I am missing.

T Chap

I don't really need the 50m except you suggested it for serial. So far the communication has been rock solid with internal only on both send and receive SX chips. I intend to use the 433 Tx and Rx however. If it works with internal using the uhf, is there a reason to still go to 50m?

Post Edited (originator99) : 9/5/2006 4:59:49 PM GMT

Bean

No reason. 50MHz is WAY overkill for the baud rates you will be using. Plus running at 50MHz will use ALOT more power.
If this is the same low-power circuit you are talking about in other threads, then I would recommend a 4MHz resonator. If you can be by with the internal 4MHz that's great. But I wouldn't recommend it.

Bean.

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·

T Chap

No luck with the 4's either.

Circuit is only the resonator across osc pins with center to GND.

Steps:

1. Program SX with Blitz using OSCHS1, 2, OSCXT1, 2 and both 50m and 4mhz res, with respective FREQ set for each
2. Remove Blitz and insert resonator after programming
3. Reset power


The program doesn't run with the Blitz plugged in using external osc modes (with no resonator in place)

I have tried 2 SX chips on two different breadboards that run fine in internal, resonator is close as possible

The chip programs so the pins must be connected on the breadboards.

5vdc on osc2
1.5vdc on osc1

No obvious clock on either pin in ac or dc modes

Bean

Are you using the SX-Tech board or your own PCB ?

Bean.

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Spend less than you make.
Make more than you spend.
·

T Chap

Using two different breadboards and the exact schematic as shown here. Although I ran across something in the manual that showed a 10k across the osc pins so I have tried that as well. When I put in the resonator the center pin goes to GND. It never causes a problem to program having the resonator in, and the Blitz manual says it doesn't cause problems usually. I have tried several different 50's and several different 4's. I always change the FREQ to the frequencey of the resonator, 4m res = FREQ 4m adn 50m Res= 50m.

John Couture

According to the SX28 prototype board, the MCLR pin is connected to a 10K resistor, THEN to VDD (+5vdc).· Bean, does that make a difference?· (I'm away from my lab so I can't test it.)

http://www.parallax.com/dl/docs/prod/boards/SX28ProtoBDRevBschematic.pdf

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John J. Couture

San Diego Miramar College

Bean

John,
· In my experience if MCLR is not connected the SX will not program either.

Bean.

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Low power SD Data Logger www.sddatalogger.com
SX-Video Display Modules www.sxvm.com

There are only two guaranteed ways to become weathy.
Spend less than you make.
Make more than you spend.
·

T Chap

I have tried with 10k and direct to 5. I have seen both with and with the Resistr on schematics, it would be great to know if the resistor is really needed.

T Chap

Update::

Bean, I discovered something. The only test I have been using for the resonators is the code posted above which is a serial Rx program. I have another Sx doing the Tx, and the code works fine on the internal 4mhz. It does not work using any variation of resonators and directives.

I just did a test with a program that does nothing but blink an led, and the program runs fine on the 4mhz resonator, so now my problem really is that the serial Rx doesn't work when using the resonator. The Tx chip is using internal osc. I'll test having the resontaor on both Tx and Rx tomorrow.

Guenther Daubach

Here is how I would try to fix the problem:

1. Write a simple LED-blinker program, connect an LED with a 470 Ohm resistor in series between the SX pin used for LED-control and ground, and disconnect the resonator in case there is one installed.
2. Make sure that the code contains a FREQ 50_000_000 directive, launch the debugger from the SX-Key IDE, and hit the RUN button.

When the LED blinks, you can be sure that the hardware is fine, and your test program as well.

3. Re-program the SX from the IDE using the "Run/Program" option to get rid of the debug code inside the SX.
4. Select "Run/Clock" from the IDE, and set the clock frequency to 50 MHz.

When the LED blinks again, you are still in good shape.

5. Quit the SX-Key IDE, power down the system, remove the SX-Key, and insert or connect the 50 MHz resonator.
6. Power up the system again.

When the LED does not blink, the resonator might be defective. If you have an oscope with sufficient bandwidth available, you might check the signal at the SX OSC1 pin. You should see a 50 MHz sine wave when the clock is working.

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Greetings from Germany,

G

T Chap

Gunther Thanks for the test ideas. The chip will run fine with the 4m resonator on an led test, but will not run on a serial Rx test at baud 9600. The chip runs fine to receive the serial trasmission when using the internal 4mhz. I have tried multiple 4 meg resonators. Sincde the led program works, ad not the serial receive program, I have some other mysterious problem that affects serial receive but not blinking programs.

Thanks

Chris Savage

Hello,

·· It seems in all cases you're not using a resonator on the Send SX.· Perhaps they're out of sync, so to speak.· I would make sure you have a 4 MHz resonator on both sides so they're at the same speed in terms of serial communication.· I hope this helps.· Take care.

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Chris Savage
Parallax Tech Support

Dave Hein

After reading all your posts I think I understand what you are doing. You have one SX chip sending codes to another SX chip over a 9600 baud serial link, right? When you say that the program doesn't run with the resonator, you mean that the receiving SX is not getting the right codes from the transmitting SX, correct? It seems like there is a mismatch in clock rates between the two chips.

The transmitting chip may be sending at a rate that is higher or lower than 9600 baud. When you use a 4 MHz resonator on the RX chip, what are you using to clock the TX chip? The clocks on the two chips must be consistent with each other.

Dave

T Chap

You guys are correct...

The moral of the story is to have resonators on both chips and save yourself a lot of frustration. Just because it works with no resonator on either side, does not mean that you can stick a resonator only on the Rx side only and expect the same results. All is fine! I can't wait for the 433 modules to be restocked.