XBee not Booting - minimum circuitry required?

Wireless & IoT Other Radios
1

I want to use XBee Pro modules in a Digimesh Network with repeat-only nodes to extend the range to more remote sensors. This is solar powered remote and I need absolute minimum power consumption. It is intended to ONLY operate as a repeater in the RF network, and have no local sensors, communications, CPU, etc. connected to any pins. I am using the Sparkfun XBee Breakout board (naked PC Board with only sockets for the XBee pins).

I hoped I could use just +3.3 VDC, Ground, and RST* with a pull-up resistor, with all other pins unconnected. It did not boot even when enclosed in a metal box (no stray ESD). It never appeared in the RF network, was never discovered in the XCTU -based network I had running, no transmissions visible in the spectrum analyzer (FieldFox with RTSA).

These XBees work fine in more complex breakout boards (both proprietary and Sparkfun USB breakouts, including USB based eval boards which use communications pins, etc).

So I added a pull-up resistor to the CONFIG* pin, thinking that may be floating wrong, but still does not boot. Is there some other pin configuration (pull-up or pull down) or power sequencing required? (I cannot find in Digi documentation or Sparkfun forum). Thanks for any info.

2

As long as the XBee has already been configured for your network, all you should need is 3.3 volt power and ground. Leave RST disconnected and see if that works.

If you put it inside a metal box, the XBee won’t appear on your RF network since it can’t communicate outside the box.

3

Thanks for the reply. I found that when I left *RST disconnected, it booted intermittently, even rarely. I am not sure what the input impedance of that pin is, but maybe stray fields would pull it up or down somewhat at random? I have found that the supply voltage cannot be much higher than 3.3, possibly 3.4 VDC, and will not boot above that value (The spec says 3.3 but I thought I could push it a bit - no go, it just won’t start above about 3.4V. So it looks like I need a voltage regulator after all. I have also tied *SLEEP high, and it seems to boot fairly reliably (at 3.3 VDC) with all three pins tied high. I have been watching for activity several ways, not just RF - the oscilloscope shows the 1 Hz square wave on one pin, and the DMM shows me when it is alive, drawing about 16.5 mA when running, and much less when it is asleep, or whatever it is doing when inactive.