User manual

WiFly GSX
www.rovingnetworks.com WiFlyGSX-um 7/16/2010
809 University Avenue • Los Gatos, CA 95032 • Tel [phone] • [e-mail]
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16. Analog Sensor Capability
The WiFly-GSX has 8 analog inputs that can be driven with 0 to 1.2VDC. Warning: over driving these
inputs will cause permanent damage. The analog inputs are sampled and the digital value read by using the
show q <channel> command.
The hardware specifications on the analog input is:
Input voltage range: 0 - 1.2V, however the A2D saturates at 400mV.
Resolution: 14 bits = 12uV
Sampling frequency: 35us
Accuracy: 5% un-calibrated
See the WiFly-GSX (RN-131G) data sheet for more details.
The accuracy of each analog sensor reading can be offset by up to 5% due to variation from chip to chip. To
improve accuracy we recommend using a precision reference voltage on one of the analog inputs to
calculate the offset. The offset will be the same for all analog inputs.
For example,
- drive precision 200mV reference on analog input 4.
- read channel 4 and compute the offset.
Let us assume for example, if you read 210mv you would know that the offset is +10mv.
When you read input 5 you would subtract 10mv from the result.
To read a sensor pin, send the following command:
show q <channel>
Channel is the analog input from 0 to 7. The value for the input channel you is measured in microvolts and
is returned as 8xxxxx. The 8 in front is a start marker.
You can also sample multiple channels by using a bit mask:
show q 0x1<mask> where mask is a bit mask of the channels.
For example, to read channels 0,1, and 7, send:
show q 0x183
The return values are the format: 8<chan0>, 8<chan1>, 8<chan7>\r\n