Since I am a newcomer in this field, I anticipate my apologies if the question is too silly!

 

By modifying tinyos-1.x/apps/Oscilloscope as suggested at http://www.moteiv.com/community/Connecting_External_Sensors , I tried to convert a 2.9 V analog signal applied to pin 3 of the 10-pin connector (i.e., the ADC port A0) of a TelosB. I got a reading of ca. 550 instead of something around 4000. Then I measured the input current when the 3-V AVCC voltage (pin 1 of the connector) is applied to pin 3 through a tester. I got a reading of about 30 mA, which is much larger than what I expected.

 

I obtained the same results considering the pin 5 (i.e., the ADC port A1) of the connector.

 

Moreover, a tmote sky device gave the same results.

 

Am I doing something wrong? What can I do to make A/D converter working with higher input impedance?

 

Thank you in advance for your attention.

 

Sandro

 

Sandro L. Fornili

Dipartimento di Tecnologie dell'Informazione

Università degli Studi di Milano

Via Bramante 65, 26013 Crema (CR), Italy

 

Tel. +39-02-503-30067

Fax +39-02-503-30010

 

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