Problem: Node supply voltage report moves along with AD1


I am new to here. Please help.
I set the node to report AD1 value and supply voltage each 5 seconds. Problem is that the node supply voltage value moves along with AD1 inputs. When AD1 gets high, supply voltage report also goes up. Please see the picture I made.

Actual supply voltage doesn’t move since no current difference occurs while changing AD1 inputs. And AD1 is the only connection to the outside, that is only connected to a tact switch now. I am just switching it high and low.

Does anybody know this problem?

Here’s my node setting:

I also performed the same input to local xbee, and read by the IS command.

The phenomenon in which VCC is similarly affected by AD input.
The test was done by S2 and S2B.

I can consider this problem on the level which should be contacted to support.

Hi Chobichan,

Thank you for trying. I will contact to the support. This is a big problem for my product. It seems I need to try reading VCC by other AD port though not sure if it won’t be affected by the other port.

Nice to know you. You are from Japan. Maybe we can meet up somewhere. I am in Kawasaki.

Best Regards,


When VCC was connected to AD1, GND was connected to AD2 and IS command was performed, 0x55 was visible to AD2.

When performing an AD conversion continuously, changing two or more analog input by one multiplexer, it is sometimes often subject to the influence of a front conversion result.

From the above-mentioned reason, also as subject to the influence of AD1, I can consider AD2.

In order to change AD input correctly, every one AD input is validated using remote AT command, and unless it uses the method of obtaining a conversion result at every time, it may not go well.

Yes,i’m in sagamihara!.

> Maybe we can meet up somewhere.

I hope so,may be next eleki-jack forum in akiba(w).

and more.

1.2V was put into AD1 input, AD2 input and GND were connected, and the following results were brought when IS command was performed.


The value of VCC will begin to be affected if AD input exceeds 2V about.
It seems that the result of other AD input will be affected if AD input exceeds 2.5V.

From this thing, it seems that it is necessary to certainly make the maximum of AD input less than 1.2V.

Thank you very much for testing the other ports!!!
1.2v is mentioned as the VREF internal volatge in the manual. I was wondering if the AD converter for reading Vcc is also used for AD ports.
So I have to 1/3 the Vcc to read from some other port. Then there will be a difficulty in accuracy with the outer resistors. I have ±5%tolerance resistors. When Vcc was 3.0v, it can be read as 3.1v or 2.9v. It doesn’t work for a bettery monitor. Getting more accurate resistors may be the most reasonable solution to it.

I will check the Eleki-jack forum!

Thanks alot,

A strange solution is found… I checked the compelete product with external circuit instead of the dummy nodes with a simple switch. Now it reports enough good stable values. Please see the capture image.

The external circuit gets a little power from Xbee’s CTS port to drive a PNP transistor. The base of PNP transistor is connected to CTS port to work while Xbee is awake. So, by some more affection from CTS or others, it helps ADC to work stable above its limit.

I hope it won’t be “affected” by future addings.

Thanks alot,


> Getting more accurate resistors may be the most reasonable solution to it.

There are 2 simple ways.

One, You can get register with high accuracy called metal film register.

The thing of accuracy can be purchased 0.1%.
The stability over temperature can also choose 25 ppm.
But it is slightly expensive.

Two,If it is network register module which is contained in one package 4 circuits, it obtains a little at a low price.

Although the accuracy on specification is not high, since the characteristic has gathered, all resistance in one package can be outputted in high accuracy, when resistance division is carried out.


Thank you very much, Chobichan.
I found a method to solve this.
I was using 1 mega ohm resistor to pull up AD1. That led AD converter to work stable. That needs killing the internal pull up. On my occasion, 1 mega ohm resisitor was needed to drive the photo transistor. This can be a useful case report to handle the Xbee supply voltage monitor in case 1 mega ohm pull up fits the reading AD port.

Best Regards,


I finally understood your advice. The thing I had to touch was AD1 maximum voltage. AD1 needs to be regulated to maximum 1.2v so that Vcc reading works fine. I changed it to 1M up and 1M down. Now it works fine. It should be 10k up and 10k down in usual AD use though.

I think this is a very important study for AD use of Xbee. AD inputs must not be over VREFI, not just can not read above it. It affects the other AD port when any port exceeds the limit.

Thank you very much.

I realized a good way to generate 1v analog source voltage without increasing the power source current. Making 1/3 voltage from RTS port will help shutting off the corrent while sleep. CTS is also good through PNP transistor.

Andy Oyamada