[W-MBUS] “The WM-Bus module on my PoC unit sometimes stops sending serial messages (eg overnight). The Radiocrafts Demo PCB continues to receive OK, so it’s not the radio signal stopping, it’s the module serial output stopping. It starts again after turning Vdd off and on. This could be radio interference on the PCB wires perhaps, eg insufficient filtering on the serial data wires or Vdd wire, so I will improve that on the PCBA. “

“I am not sure if I clearly understand your test setup, but there are two things which can cause the module to behave strange;
– RXD-pin, into the module: If your PIC at any stage (during sleep or startup) does not drive the RC1180 with push-pull output, insert a 8k2 (or less) resistor between the modules RXD-pin and VCC. The CMOS input is quite shaky and need
distinct high and low voltages
– Reset: Same issue here, it need to be either well filtered or have low AC-impedance to GND (or VCC). So best solution is to short-circuit the Reset-pin (pin 12) to VCC. This must be removed before any re-flashing of the module, but is no
topic right now
Apart from these, no other issues are noted which can cause the module to malfunction.

Last Update: November 9, 2017  

November 9, 2017   910    Wireless M-Bus Q&A