Could I use the RSSI signal to determine signal strength? Can someone suggest a simple circuit that I can visually display the signal using a LED bar graph.
According to my d/s, RSSI is a PWM output. You can filter this using a simple RC low-pass filter, and feed to an LM394 or LM3915. They apparently still make these things.
For ckts, do a google image search on LM3914 or LM3915,
Well I have a PCF8574N. Will that work?
Ok, take at look at the chips I mentioned and see how they compare to your [what I presume is an] I2C expander. You want a display, no?
Ok, take at look at the chips I mentioned and see how they compare to your [what I presume is an]
I2C expander. You want a display, no?
I looked at the LM3916, and I realized the difference after I posted that. One is a multiple LED/LCD driver and the other is an I2C expander for an LCD.
What values would you suggest for the Low Pass Filter?
You need to know the PWM frequency out of the RSSI pin, and then select a cutoff frequency roughly 10X lower, according to
F3db = 1/(2*pi*R*C)
Use R=4.7K or 10K as a starting point and calculate C accordingly. That's where I'd start.
take a look to dev interface schematic, were a lm339 is used to drive 3 leds (basic comparator) feed with rssi output through RC filter
I'm working on a project right now that does this. Connect the XBee RSSI pin to a digital input pin and use pulseIn() to read the PWM pulse width.
S1 or S2 XBees?