No AT Response from SLM on BLG840F (nRF52840 + nRF9160)

[Thanu]

• Hardware: Fanstel BLG840F (nRF52840 + nRF9160, internally connected)

• Firmware Setup:

  • nRF52840 running custom firmware using nrfx_uarte (TX/RX to SLM)

  • nRF9160 running Serial LTE Modem (SLM) firmware built with NCS v2.8.0

• created the slm firmware using NCS v2.8. 
• 
  

  &uart0 {

      status = "okay";

      current-speed = <115200>;

      pinctrl-0 = <&uart0_default_alt>;

      pinctrl-1 = <&uart0_sleep_alt>;

      pinctrl-names = "default", "sleep";

  };

  
  

  &pinctrl {

      uart0_default_alt: uart0_default_alt {

          group1 {

              psels = <NRF_PSEL(UART_TX, 0, 23)>, <NRF_PSEL(UART_RX, 0, 22)>;

          };

      };

      uart0_sleep_alt: uart0_sleep_alt {

          group1 {

              psels = <NRF_PSEL(UART_TX, 0, 23)>, <NRF_PSEL(UART_RX, 0, 22)>;

          };

      };

  };

  Then NRF52840 sending at comments but no reply from nrf9160 

  

  output from rtt viewer 

  System starting...
  00> UART initialized
  00>
  00> Sent: AT
  00>
  00> Sent: AT+CFUN=1
  00>
  00> Sent: AT+CGMR