We are using the nRF9160 with modem version 1.3.2 and SLM version 2.0.0. We have our unit in eDRX mode, using flow control on UART0, and only get WakeUp interrupts when we receive a SMS message, which is exactly what we want. All that works great but I believe we are supposed to ACK incoming messages. When I send the ACK, the response was always “+CMS: error 0”. Various notes from Nordic online say you need to send an ACK or else the SMS service will be terminated but since we are receiving the message unsolicited, there is some debate about the ACK being automatic.
I can only find examples of sending messages, not receiving them with the SLM app. I tried AT+CNMA and also AT+CMNA=1 for ACKs but get the same result. My question is, do I need to send an ACK and if so, how do I do that so I don't get an error?
