LowPowerLab Forum

Hardware support => Moteino => Topic started by: chalupien on March 18, 2014, 07:56:20 PM

Title: RFM69HW and Uno
Post by: chalupien on March 18, 2014, 07:56:20 PM
Ok so I've been reading around that I need a voltage divider or level shifter to communicate between the 5v uno and the 3.3v RFM69. However I have the example sketches running on two uno's with the rfm powered by the 5V output. I tested the Voltage going into the RFM and it's 5.2V and 4.8V. Reading that this will damage the RFM? It seems to work just fine... Why? and Is this bad?

Title: Re: RFM69HW and Uno
Post by: Felix on March 18, 2014, 08:13:16 PM
Quote from: chalupien on March 18, 2014, 07:56:20 PM
I tested the Voltage going into the RFM and it's 5.2V and 4.8V. Reading that this will damage the RFM? It seems to work just fine... Why? and Is this bad?
Oops, maybe not for long...
Title: Re: RFM69HW and Uno
Post by: chalupien on March 19, 2014, 01:16:40 PM
So at the minimum Ill need to shift the voltage down by passing it through a series of 10k/4.7k or 2.2k/1k resistors? What size can these be? 1/4W 1/6W??

Nick
Title: Re: RFM69HW and Uno
Post by: Felix on March 19, 2014, 07:33:21 PM
They are signal shifters so minimal current will leak, get the smallest you can handle