RFM69HCW breakout is wrong chip?

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joeryan11
 
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RFM69HCW breakout is wrong chip?

Post by joeryan11 »

I've used several RFM69HCW modules in my projects over the years. I used to order the Hope RFM69HCW modules through another supplier, and then adapt them for use on a breadboard. No issues, just extra effort on the soldering work. For many years, I've had the same working code that can TX/RX up to +20 dBm output.

About a year ago (I think), I purchased some of your Adafruit RFM69HCW breakouts. (Time passed). The two that I've put into projects recently do not function properly at TX power levels above +13 dBm. Funny enough, that's the cut-over point between the RFM69 chip and the RFM69HCW chip, the latter supporting +14 dBm up to +20.

So... was there a manufacturing mistake where you put RFM69 modules onto your RFM69HCW breakouts? Because I can't find any other explanation for this. And unfortunately according to datasheets, both these chips return 0x24 from RegVersion (register 0x10). So apparently software can't tell them apart (between the regular and "high power" version). I was also looking for how the actual chips are stamped on top of the IC, but Hope doesn't really make it clear in the datasheets.

I have the 433 MHz version of the RFM69HCW breakouts, and they are stamped with a red dot on the radio IC. Here's the top of the radio two radio ICs, in case this info helps:

RF69
1706
W4C248

RF69
1613
W3G957
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adafruit_support_mike
 
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Re: RFM69HCW breakout is wrong chip?

Post by adafruit_support_mike »

I don’t know of any issues with getting the wrong chip variant, and this is the first report I’ve seen of that issue.

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joeryan11
 
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Re: RFM69HCW breakout is wrong chip?

Post by joeryan11 »

Thanks for the reply. After more testing, what seems to have been the issue is EMI interference onto a CLK_OUT line from the RFM69HCW breakout. I'm using the more precise crystal inside the radio module to generate a clock signal for my RTOS, rather than the less precise DFLL-based internal clock from the Itsy M4 (I wish you had included an actual crystal here, and not put it only on the Feather M4 breakout; the Itsy M4 is perfect, it just needs a 16-25MHz crystal at the same price point, please!).

With higher TX power from the radio, EMI starts to mess with the clock signal into the MCU, causing the issues I was seeing (time jitter).

Good lesson in routing CLK lines *under* the ground plane of the board, and being more careful about the location of GND connections into the ground plane, to avoid accidentally creating an antenna loop. I was able to fix my issue with more careful routing of the circuit.

One more thought: shielded ~22 AWG hook-up cables (single, solid conductor) would be cool for Adafruit to stock. I haven't had an easy time finding them for sale on Digikey, Mouser, Arrow. Unless you want twisted pair stuff (like Cat 6). I assume I could've kept the CLK line above the ground plane if the cable was shielded, but who knows.

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