Author Topic: diagnosing problems and my journey with nano  (Read 122 times)


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diagnosing problems and my journey with nano
« on: February 20, 2020, 07:36:43 AM »
I struggle to get my rfm69hw to talk to eachother. And im running out of ideas. This is the log what i was doing, so maybe someone else got same symptoms.

First nano is 5V and rfm69 works on 3,3V. Nano has 3,3 power source and i used it to power rfm69 chip, but logic gates where on 5V.
Soldered all the wires and booted them up with standard gateway and node example, nothing happens first. Then i thought maybe some wires are loose and keep checking. Weirdly enough, connection established when i touched gateway ground and 5V power with my hands.  got RSSI around -50 while they keep a meter apart. Thought, maybe its because 3,3v-5v communication is failing and got some logic converters. soldered them between and tested again. No connection. Got separate 3,3 power source from a shield, exact same result.

So i thought, lets check if communication works between arduino nano and rfm69. Sended 'r' command trough serial port and got registers. Gateway seemed ok, node sended only 1-s. Seemed wiring problemm - replaced whole rfm69 chip and got node working with registers.Tested A2 port with sending high in it, both react but there is no data to transfer. i concluded, that wiring must be correct on both boards.

So i now need bit of help to test where the problem could be. Is there a way to test if antenna is sending something. And ig gateway is registering anything? ideas?

Uncle Buzz

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Re: diagnosing problems and my journey with nano
« Reply #1 on: February 23, 2020, 09:58:33 AM »
On real nano, 3V3 is provided by the FT232RL (USB chip)...
from datasheet of FT232RL, you can read
3V3OUT can be used to supply external circuitry requiring a
+3.3V nominal supply with a maximum current of 50mA.

Since RFM69 needs 16mA in RX mode, and 16 to 45mA for RFM69W/CW, 16 to 130mA for RFM69HW/CHW depending of power settings, you probably ask to much power from your 3V3 supply.
Try to set lower power first to confirm this, then add a 3V3 regulator to supply your radio.

If your nano is a chineese copy, you have to check the maximum current provided by their USB chip which is probably not a FTDI one, maybe with more or less current capability...
« Last Edit: February 23, 2020, 10:00:56 AM by Uncle Buzz »