[W-MBUS] “we have a problem with the configuration of RC1700HP(MBUS4). We start our micro and we start the comunicacion for the uart with the radiocraft RC1700HP likewise with the RC1180 MBUS3 (with a low level in the nConfig pin) but the Radiocraft RC1700HP don’t responde (with the symbol >). We watch with the oscilloscope that in the pin RTS/SLEEP in this case we have a High level and in the RC1180 we have a low level, could be this the problem, you know why can be? The supply that we use for the RC1700HP is Vcc = 2.5v and Vcc_PA = 3.6v. Is this ok? “

“If the config-pin is asserted low twice, it will not give prompt the second time. So if the module is already in config-mode after power-up sequence (if config-pin voltage raise slowly compared to VCC), then it must have a Reset low before
config can go low again and module will give new prompt. If you try Reset + config in a sequence from a controller (or manually), then you should see prompt ‘>’ for each config low.
It can also be a problem if the RXD pin is floating during your tests; Then the CMOS input might cause a lot of characters to be sent, and then I am not sure how config-mode will behave. So during all tests, use a maximum 8k2 ohm resistor as pull-up to
VCC.
Your voltages are ok, the module should work fine.
The RTS/Sleep pin does not matter unless the module is configured for using this pin, but in the default mode it is not used

Last Update: October 5, 2017  

October 5, 2017   1164    Wireless M-Bus Q&A