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www.rovingnetworks.com
Version 1.0r 9/21/2012
79
RN -W IFLYCR -U M
ANALOG SENSOR CAPABILITY
The module has 8 analog sensor inputs that can be driven between 0 to 1.2-V DC. You can sample the analog inputs and
read digital value using the
show q
<
value
> command, where <
value
> is a decimal number representing the channel. See
“show q <
value
>” on page 36 for more details.
WARNING:
Driving these inputs above 1.2 V can permanently damage the module.
The channel is the analog sensor input from 0 to 7. The value for the analog sensor input is measured in microvolts and is
returned as 8
xxxxx
, where the beginning 8 is a start marker.
You can also sample multiple channels by using a bit mask using the
show q 0x1
<
mask
> command, where <
mask
> is a
bit mask of the channels. See “show q 0x1<
mask
>” on page 36 for more details.
Example: Read Channels 0, 1 & 7
show q 0x183
// Read channels 0, 1, and 7
The results are in the format
8
<channel 0>
, 8
<channel 1>
, 8
<channel 7>
\r\n
The analog input hardware specification is:
Input voltage range:
0 - 1.2 V, however, the analog-to-digital converter saturates at 400 mV
Resolution:
14 bits = 12 uV
Sampling frequency:
35 us
Accuracy:
5% un-calibrated
The accuracy of each analog sensor reading can be offset by up to 5% due to variations from chip to chip. To improve
accuracy, Roving Networks recommends using a precision reference voltage on one of the analog inputs to calculate the
offset. The offset is the same for all analog inputs. For example:
•
Drive precision 200 mV reference on analog input 4.
•
Read analog input 4 and compute the offset.
If you read 210 mV you know that the offset is +10 mV. When you read input 5, subtract 10 mV from the result.
Sampling Sensor Pins Automatically
The sensor pins can be sampled automatically and data forwarded in two modes:
•
The UDP broadcast packet can contain the sample values.
•
In HTTP mode, the sampled pin data can be forwarded to a remote server
To enable these modes, use the
set q sensor
<
mask
> command.
Example: Sample All Sensor Inputs
set q sensor 0xff
// Sample all sensor inputs