BOE-DAR project & SureLink data noise

JED1

Does anyone know how to deal with the noise on the signals of the SureLink in the BOE-DAR project? I have been trying to implement the BOE-DAR
project and almost have it completed. In following the instruction on the application note (page 8) instead of getting the orderly progression of data
in the debug screen as shown. I am getting the following (just powered on and not started in the routine, if I start it you can see the real data change
in the data stream.)

80800040!8

Chris Savage

Hello,
·· It should be simply enought to isolate if the noise is coming from the transmitter or receiver.· Simply turn off the transmitter.· If you're still getting noise, it's being picked up by the receiver.· If not, it's probably being sent by the transmitter somehow.· I still fail to see how the noise would cause the program to not be able to open the COM port, but I will attempt to find the author and see if I can get him to jump in on this one and see what he thinks.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

Phil Pilgrim

Hi JEDI,

This looks like a communication problem between the SureLink host adaptor and your PC. Some suggestions:

1. Make sure the SureLink is set up to use RTS/CTS flow control. (There's a checkbox for that in the SureLink setup screen.)

2. Make sure that the serial cable connecting the host adaptor to your PC is fully wired for hardware handshaking. A simple 3-wire cable having only RX, TX, and GND will not work here. The RTS and CTS lines need to be present.

3. Make sure you have a fresh 9V battery powering the SureLink host adaptor.

If none of this works, try testing with a wired connection. Change the line in the BS2 program that reads:

RFXmt PIN 0

to:

RFXmt CON 16

This will transfer the SureLink comms to the Debug port so you can examine the output directly. If you see the same problems here, you may need to switch to a lower baud rate.

'Hope this helps...

-Phil

JED1

Thank you Chris and Phil

First Chris, I also thought of that but failed to tell you in the first write up that when I turn off the receiver that the data (and noise) update in the debug
Window also stops as I would expect.

Phil I performed all your suggestion as well.

1. Yes the RTX is tag and when it is not no data will appear plus I can see the RX screen indicator active when the data is being updated.
2. While I haven't run out the cable yet. The fact that I was able to see the RX indicator pulsing I believe is a pretty good indicator this S/B okay.
3. I also this on both the BOE and the SureLink Host adapter.

When I do your last suggestion I get a nice and clean debug screen (no noise).

I have also tried the following with no real success.

I purchase a couple more SureLink Modules and programmed it first a point B and then swapped it with the original. Then I did the same for the other Point A.
No noticeable change.

I put filter caps on the Boe board one at a time 0.01 .1 and a 10 across the GND and VDD with not improvement.

I have rewired and positioned the module on the BOE twice. The first time is the only time I believe I saw some improvement (but still not clean).
The second looks worse.

I tried switching the SureLink host adapter and that didn't change anything either.

I believe it is the wiring environment on the BOE proto board that is the cause.

I am going rewire the BOE again. I don't have the RF module with pin hanging off my board. I was able to carefully put all the LED / IR and wheel
Encoder on the front half of the proto board and dedicated the portion closest to the STAMP to the SureLink RF Module.

I have also gone to the Needham's web site and looked over the Users manual and web page on the SureLinks with no real new clue as what to try next.

Any other suggestions are welcome.

Jeff

Chris Savage

JED1 said...(trimmed)
Thank you Chris and Phil
First Chris, I also thought of that but failed to tell you in the first write up that when I turn off the receiver that the data (and noise) update in the debug
Window also stops as I would expect.

Hello,

·· My suggestion was to turn off the transmitter, not the receiver.· Turning off the receiver is going to turn off all the signal, and is thus not a usable test.· Turning off the transmitter as I suggested would tell you if the interference was coming from the transmitter or if the receiver was just picking up noise from the air.

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Chris Savage
Parallax Tech Support
csavage@parallax.com

JED1

Thank you Chris That was my typing error I have also turned off the transmitter only. The debug screen stops with updates and will remain so until the transmitter is
turn back on. Of course the link LED extinguishes on the receiver when you do this.

Jeff

JED1

I tried to move the RF module to the BOE expansion application board to see if that might help. But it made no change.

Phil, Please tell me what exactly are the entire jumper setting on your QuickLink RS232 module I am wondering if I have something not right here.
I have followed the setting in your application for the programming of the RF module and am quite confident it matches.

In the Needham's User manual they make a statement under the Command/ AT Command Mode section that states that in order for a peripheral to receive data from a command unit the address must be set to something other than 0000. If I am not mistaken we should be good in that the notes show this set to FFFE, is that correct? On the same tab for the surelink_control.exe what S/B the UART settings? The notes show 57600 Baud 8,n,1 Hardware. The only aspect that could be a wild card is your note at the top of page 3 concerning this. Is there a simple test you know of, to determine which is needed? Have you used that display window?
I tried it and got similar results once again.

Jeff