PACKET_CAPTURE_THRESHOLD vs collision detection

[xaelsouth]

PACKET_CAPTURE_THRESHOLD vs collision detection

[xaelsouth]

The idea behind the code snippet you referenced - "if (rssi < PACKET_CAPTURE_THRESHOLD) { reset_t1_c1_packet_decoder(decoder); }" - was as follows:

Stop receiving by resetting the state machine if the signal currently being received gets weaker und falls below a threshold = PACKET_CAPTURE_THRESHOLD. So we don't waste time with a weak signal, which we probably would never have received at good quality, and prepare us to receive the stronger signal instead. It's assumed that the stronger signal could begin even before the weak signal is completely gone!

A collision occurs when a weaker signal is going to be overlapped by a stronger one, not the oher way around.

You can disable this kind of collision detection by setting PACKET_CAPTURE_THRESHOLD = 0.

Collisions should not occure equally often, assuming sending datagrams is correct implemented. Each device maintains a pseudo-random offset to sending time, which should help to eliminate cycling and collisions in sending schemas.

[xaelsouth]

To device's battery status which is reported to be ok. Batteries embedded in metering devices are often not very powerful to provide enough current to RF transceiver for sending datagrams. A small electrolytic capacitor near to the battery solves the problem with load peaks. May be that the capacity is to small or degrades with time or is too sensitive to external temperature, so that your device is sending with less power?..

[pswiatki]

It is possible, but all water meters in the vicinity come from the same water company - I believe they are the same type (and the mandatory replacement dates are not too far away). So, if there is a hardware malfunction, it is in my own meter, because I can easily pick up other, more distant ones and the reported RSSI is much higher. By the way, I also have the power meter (amiplus) in the basement of the building and its reported RSSI is always well above 130. Must be very strong transmitter (signal goes through a thick, brick/concrete floor and several meters up to the RX antenna (which it hits from a wacky angle of 90 degrees to the boom of the 10-element yagi). Yet, it doesn't affect the RSSI level a single bit. But hey - power is not an issue for.... a power meter, right? ;)

Frankly speaking: I had a plan to make a portable scanner (perhaps the RPi running wmbusmeters and GPS) and somehow conceal the yagi, then go for a walk ;) It would give me a pretty good idea of what I should expect from my own meter (compared to other meters with their known locations and therefore also distances from my original RX rig in the house.