[W-MBUS] “I configured the MBUS radio to use the UART flow control using the CTS/RTS pins. When the host processor wants to send an MBUS message, it pulls the RTS pin low and waits for the radio to pull CTS up. The processor then sends the message. But this gives strange results, and sometimes it just fails to send the message. I also tried using only the CTS pin, where I wait for the pin to go high before sending the message. Again, this does not always work. Are the CTS/RTS pins exclusively for controlling the flow over the uart connection (host processor to radio) or are they meant to indicate when the radio can send another message ? If so, how should I use them ? “

CTS informs that the module is busy when it is high. It can be busy if it receives a packet over air or if it transmit a packet. Note that it is busy and CTS is high both during the actual reception/transmission and during baseband handling of the data to/from UART. I have enclosed a time plott when the slave send 5 bytes over UART and the master receive the Header + 5 bytes. CTS is enabled and informs when the module is busy.

Last Update: November 9, 2017  

November 9, 2017   1225    Wireless M-Bus Q&A