RFM69 HCW in low power mode possible?



  • Hi there,

    A quick question: Does anyone know if the libraries for the RFM69 allow to use the HCW in low power mode?

    I would prefer to use boards with HCW layouts instead of 2 separate ones for HCW and CW to be more flexible.
    But I'm not sure if
    a) the HCW can be used in low power mode and b) if it equals the power consumption of the CW (or if there are any benefits
    using the CW).

    I heard that some libraries allow auto adjusting the transmission power based on the RSSI - does anyone know something about this?

    Thanks a lot,
    Christoph


  • Hero Member

    @chbla said in RFM69 HCW in low power mode possible?:

    Does anyone know if the libraries for the RFM69 allow to use the HCW in low power mode?

    By "low power mode" are you referring to reduced Tx power or something else?


  • Hardware Contributor

    @chbla
    i have not tried to use HCW in low power mode, but it should work.
    CW or HCW are using the same ic. But to have better RF perf, HCW has more electronics to amplify RF etc.
    So we could say CW is more optimized for low power, but no big difference in power down mode. The big diff would be in TX&RX modes that's all. But that can be tuned with autoadjusting. for this take a look at ATC in docs, or in myconfig.h to know the defines to use.



  • But CW and HCW share the same footprint! The only thing you'd have to change is to add #define MY_IS_RFM69HW for the HCW version to your code, and leave it out if you use the CW version.

    The exact same counts for the non "C" versions. The C in the type designation means it's pin compatible with previous versions of the radio (RFM12).

    But to answer your questions:
    a) the transmit power of the both is adjustable, the minimum level of both is the same, the maximum of the HCW is 7dB higher with a power consumption that is 3 times higher as the CW.
    b) when set at the same level, the power consumption is the same.

    But like I said, no need to start putting these tricks in. Just solder the right module on the PCB and add the #define accordingly in your code.


  • Mod

    @chbla if you enable the new driver it will adjust the TX power accordingly


  • Hero Member

    I thought there were technical reasons (the particular RF switch that Hoperf chose) that the RFM69HW couldn't go lower on its Tx power. Are you sure the same doesn't apply to the RFM69HCW?



  • They don't exactly share the same footprint. The HCW has 16 pins and the HW only 14. The 3V3 location does not line up, so it seems like you need a different mounting pad for each type. The radios I received in the mail match the pinouts from the data sheets on HopeRF. Is there a way to use these on the same pads that I am not seeing?


  • Hardware Contributor

    @davidzh said in RFM69 HCW in low power mode possible?:

    But CW and HCW share the same footprint!

    No.. they don't share the same footprint.

    But to answer your questions:
    a) the transmit power of the both is adjustable, the minimum level of both is the same, the maximum of the HCW is 7dB higher with a power consumption that is 3 times higher as the CW.

    I don't remember exactly (that's a while I worked on the driver) but there is a little limitation in registers, regarding granularity which could make HCW a bit power hungry like neverdie said. but take it with a pinch of salt as I don't remember well. and that's regarding emit/TX mode so that's not a big problem as I imagine your node won't spend his time in TX 🙂
    What would impact is if you were using HCW in high TX power levels (without adjusting) with the wrong power supply (not enough powerful)



  • I was referring to the TX power, right.

    Thanks a lot for the answers! I guess in this case it's much more more flexible to go with the HCW layout.



  • @davidzh Further to what has been already said, you can see the different chips if you scroll down the page on the Moteino site.

    The W and HW share the same footprint, but not the CW and HCW.
    I had previous experience of buying CWs for a job instead of the W due to a "misprint", but then realised I had to be careful which future project they were used on since the smaller version does not share the same footprint...
    link text



  • I stand corrected about the footprints.
    But wouldn't it be an idea to choose the non "C" version for your PCB?
    The price should be exactly the same (at least it is at the supplier here in NL where I get mine from) at the cost of a slightly bigger footprint (3.7 mm wider in one direction, the other is the same).

    Sorry again for the confusion caused.


  • Mod

    Agreed, I'd go for the W and HW footprint in order to use same pcb for both models according to your needs



  • @gohan that’s what I use in my setup - W and HW.
    The only exception is those Lora compatible Moteinos where I have to use either rfm95 or rfm69hcw so I’m going for the HCW version.


 

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