# Stuck at "Getting Param"

If I’m trying to scope the signal, which pin do i measure across? And what sort of signal should I be observing to know that it is the right signal

No. Tx means transmit. Rx means receive ie. DOUT to RX.
You only need one board for the airside. The link you posted is good.
You measure between GND and TX or RX. You need to make sure the levels are valid logic levels. See learn.sparkfun.com/tutorials/logic-levels

Yup I got your Dout to RX and Din to Tx
Do I measure the TX/Rx and ground from the apm board?
Can I use a digital multimeter instead of an oscilloscope? Or I have to see the signal to verify i got a logic 1.

I’ve measure using multimeter across Tx(apm side) to ground and Rx(apm side) to ground and both gave me around 5volts value

You cannot use a multimeter. And the main issue is not the logic 1. But logic zero not being low enough, ie lower than 0.7V

Okay, i will get back to you on Tuesday because I only be able to use an oscilloscope on then. Thank you for your help billy!sorry for taking much of your time

Last qns, if I manage to find out that my logic 0 is not low enough at my apm side, i have to solder out the components?

I have called the shop that sells the xtreme xbee adapter board, and they are out of stock… so my last bet is on this explorer board

Yes, you will need to remove the components.

Check DOUT is the correct levels first, and remove Q2 and the two resistors next to it, if it is not. Then check to see if it works, if not check DIN and then remove Q1 and the resistors.

See updated diagram for help

You mention adding inline resistor to have a better voltage drop… Do I have to consider that?

I couldn’t find an Input Voltage Max definition in the XBEE data-sheet. My guess is that data-in should ideally not be >3.3V. Measure the voltage of what would be connected to DIN and if it’s higher than 3.3V add a series resistor to create a voltage drop to be below 3.3V. Try a 1K. What I suspect will happen is not much as the input impedance is high, so little current will flow and it will work with or without the resistor.

The reason I am being cautious is that I did the mod with a Roving Networks Bluetooth module with a XBEE footprint. RN-41. It’s also a 3.3V part. I didn’t use a resistor and it worked by removing the parts as described. I haven’t tested the same with an XBEE, but the same theory applies…

If you really need it to work now, remove Q1/Q2. And resistors. But you may damage the XBEE without a resistor in series, or buy the XBEE Extreme adapter if you don’t want to risk it.

I honestly think you will be fine, but there is that chance, and without me testing it personally I just want you to be aware of that.

I wanted to get the Xtreambee board in Singapore, and the shop i searched for does not sell this product anymore. Also 3dr does not provides shipping to Singapore already

Btw the signals which I’ve to measure across the oscilloscope is “DOUT” or “OUT”

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I have two question after reading the website you sent me.

1. The signals I’m measuring across the XBEE both are Voltage Output??

2. I should measure at Location 1 or 2 at the image shown above and are the values I stated the right amount of value to indicate a valid logic

DOUT or OUT. you can measure at both points. With the components in place, the levels should be as you have indicated. Though 0.3V at OUT would be better.

The levels you are measuring are in respect to GND and are the voltage of the signal lines. OUT and IN represent the signal and if the signal is control by thay device i.e. OUT or by an external device i.e. IN.

Hope that helps

Hi Billy, you mentioned on Input Voltage Max definition in datasheet and i came across while researching the datasheet of my XBEE and i found this website
http://www.digi.com/support/kbase/kbaseresultdetl?id=3522#General
Under the General information i saw "
The ADC on XBee radios are 10-bit, which will provide a resolution from 0 to 1023 (0x03FF). Each XBee has varying requirements for acceptable ADC voltage ranges. Please refer to the individual product manual or the chart below for the XBee you are using in your design. Regardless of which XBee you chose, you must not exceed 3.3V on any pin or you will damage the radio module.

Does that mean that If i remove the fets and resistor my Out will be exceeding 3.3volts as it is becoming 5Volts, will I have a problem with this?

[quote=“billbonney”]I couldn’t find an Input Voltage Max definition in the XBEE data-sheet. My guess is that data-in should ideally not be >3.3V. Measure the voltage of what would be connected to DIN and if it’s higher than 3.3V add a series resistor to create a voltage drop to be below 3.3V. Try a 1K. What I suspect will happen is not much as the input impedance is high, so little current will flow and it will work with or without the resistor.

The reason I am being cautious is that I did the mod with a Roving Networks Bluetooth module with a XBEE footprint. RN-41. It’s also a 3.3V part. I didn’t use a resistor and it worked by removing the parts as described. I haven’t tested the same with an XBEE, but the same theory applies…

If you really need it to work now, remove Q1/Q2. And resistors. But you may damage the XBEE without a resistor in series, or buy the XBEE Extreme adapter if you don’t want to risk it.

I honestly think you will be fine, but there is that chance, and without me testing it personally I just want you to be aware of that. [/quote]

This is why I suggested Q2 and resistors first, as this is the line out from the module, not the in. If you remove Q1 which is the line in (data in) if you put a resistor of 1K in series with the connection, it will protect against the voltage damage, but it maybe to large and still not work, you just need to measure the voltage on the pin to XBEE and see if it complies with the levels.

The impedance to the input lines in quite hight, so even though they say don’t go over 3.3V sometimes it works. It works ok with the RN41 Bluetooth module. One way of seeing if it works is to try, if it doesn’t you will blow up the module, but if it works, it works. You choice to try it, otherwise wait till you can get a XTremeBee adapter.

Have you tried, or are you still waiting for further advice?

Thanks

Thanks Billy, I wanted to try it out this week. but something crop up with my schedule so I will be only to test it out on Monday, Sorry for the delay!

Hi Billy, I’ve accidentally damaged my old explorer board, and the 5V and GND seems to be shorted permanently already, so I went to purchase a new one and tested.

This new board was actually able to connect the XBEE to mission planner! Hooray!. Nevertheless, I have use the oscilloscope to test the signals and both the high and low are at the acceptable logic level. However I can see some sharp spike and if my quad is quite farm, let say about 5m? The mission planner screens starts to have a slight delay of updating the states like roughly 1 second, is that fine?

That’s good news.

If you go 20m away, does it improve? when you are really close the signals can swamp each other.

It won’t make any difference if the update rate slows. It won’t have any negative effect other than latency increasing

I had immediate solution to this when I unchecked RTS CTS (old serial connection “hardware handshake” protocol from the modems stone ages) check boxes for both 3DR Radios here in Mission Planner Initial Setup/3DR Radio. If you cannot resolve changing the checkboxes using the MP interface, use your FTDI configuration adapter and config software.

RTS CTS probably has this effect because your radio (like mine) does not implement RTS CTS hardware connections between it and the APM. Old modems “in the day” used these 2 extra crossed over wired lines between the computer (terminal) modem to synchronize data transmissions. Looking on my 3DR radios, these signals are not broken out to the connector, nor are they on the APM, so it makes no sense to use these settings in software without the hardware support. Other radios may use these, but APM doesn’t, so the same problem would also exist in that case as well. In this situation Mission Planner does the best it can with erroneous information.

I use a RFD900+ modem with Pixhawk cube. I have this same issue. All my wiring is correct as the same setup was working a couple of days ago, now it suddenly gets stuck at “getting params” forever.
I have tried swapping modems, autopilot, different cables, different batteries, different GCS but with no luck. Any suggestions?
Thanks,
Karthik