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What is the max input voltage for the ADC pins? I thought it was 3.2V and not 1.2V like I've been reading.

Second, I am trying to setup ADC 0 and 1 to transmit to PWM 0 and 1. Here are my settings:

Transmitter:
DL 1234
MY 5678
D0 2
D1 2
IR 14
IT 5

Receiver:
DL 5678
MY 1234
PO 2
P1 2
IU 1
IA FFFF

Using the terminal I am able to see the data stream coming into the receiver. However, the voltage changes from 0V to 3.2V (no in between values) when I moved the joystick from 0-1.2V. I do not need the data stream, I need the voltage at pin 6 and 7 to reflect the movement of the joystick. Any ideas ? Thanks.
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What is the max input voltage for the ADC pins?
On the XBee? 3.3V.

Quote
I thought it was 3.2V and not 1.2V like I've been reading.
Reading where?
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According to the datasheet (page 17 - "DC Characteristics of the XBee/XBee‐PRO") the ADC input voltage range on a XBee series 2 is typical 1.2V and max. VREFI (internal reference voltage).

There is a note on the "DC Characteristics of the XBee/XBee‐PRO" table referring to the ADC input also:

"Note – The signal-ended ADC measurements are limited in their range and only guaranteed for accuracy in
the range 0 to VREFI. The nature of the ADC’s internal design allows for measurements outside of this range
(+/- 200mV), but the accuracy of such measurements are not guaranteed."

I can't find any maximum numbers for the ADC inputs in the datasheet though.

A simple way to step down the original voltage (in this case 3.2V) might be a simple voltage divider consisting of two resistors. If you look for very fast signals you might consider specialized level shifter ICs.

markbee

« Last Edit: July 23, 2011, 11:58:55 pm by markbee » Logged


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I should of added it's a Series 1. I looked at the datasheet again. It says from ADC Vref is from 2.08V to V_DDAD which is connected to VCC. VCC is 3.4V. So it looks like PaulS was right. Again  smiley I'm pretty sure you've answer more of my questions.

But it still doesn't explain why I don't see the pin 6 or 7 change when I move the joystick. Ugh.
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Vref according to the Xbee pdf says max is V_DDAD which is connected to Vcc. It's not. Connect Vref to Vcc. Problem solved.
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