I bought from a local hardware store some RFM69CW modules. The CW version of the RFM69 is pin compatible with the RFM12. I ordered 6 modules with 868 MHz. Two prototypes are working as expected, the other 3 do not. I did a lot of debugging but in the end I fear that the modules are not 868 MHz modules but 433 MHz modules because with "#define FREQUENCY RF69_433MHZ" this modules are working smooth. With a 868 MHz code they working sometimes, especially when you touch the antenna. But the most time they do not work. From the 6 samples I have one un-soldered left and there is a black hand painted dash at 868 MHz. I think it was the same on the other modules but I can not verify it because the side witz this note is placed on the PCB.
My question is: Can I find out what hardware frequency a RFM module is by special components on the PCB or by software? I can not damage my prototypes (it's a bee hive monitoring system) but want to finde out what RFM modules I have really on my board and I want not to trust the invoice I got from the seller. Can anyone help? Are 868 vs 433 RFM69CW the same in the hardware you can see on the PCB? If not, can I find this out via (Arduino) Software?
You cannot determine in software any of the settings of the module (W/HW or frequency). These are implemented on the hardware side. The only indication is the black marker on the underside.