Summary of RFM69 output power
The article discusses the author's experience with the RFM69HW radio module, chosen for its higher power capability and cost-effectiveness. Despite the datasheet indicating the ability to reduce power output to -18dBm for low-power operation, the author encountered issues when mixing standard W and high-power HW modules. The Radiohead library used (version 1.71) enforces power limits that differ between the two module types, causing compatibility problems. The datasheet clarifies which power amplifier settings apply based on output level, but the overlapping ranges complicate seamless operation across both module types.
Parts used in the RFM69HW Module Project:
- RFM69HW radio module
- Radiohead library (software component)
As I was mentioning in my 1000.1000 Hardwareselection, I have opted for the cool RFM69HW radio module. Weirdly enough, in quite a few sources (big distributor and ebay) the higher power HW module is cheaper. So there ie no reason not to get the higher power module, given quantity discounts. But I want it to operate at lower power most of times. The datasheet does not show any differences at lower power, so I had no reason not to go for the higher power module. It even says so on the features list on the front page, I can turn the power down to -18dBm.
What happens?
Unaware of the full details, frustration emerged when I started mixing in both types of modules. The Radioheadimplementation I am using (1.71) makes sure no single power value will work for both module types: over 13 dBm and a W module will not work, under 14 dBm and a HW module will not work. Digging through the code shows no problems, it does not really work as expected, but it should. The datasheet makes things more clear which power amplifier to enable based on the level and the library implements it properly. We can see there is some overlapping in the ranges as well.
for more detail: RFM69 output power
