Modem reboots during RS485 Port read and while modem is latched to network

Hi ,
The sierra modem reboots when below operations are performed concurrently,

  1. Read data from RS485 port1
  2. Modem is latched to the network.
    This reboots the entire system and no clue in the dmesg logs.
    Could someone help us in getting it resolved.


Which module are you using?

What do you mean by latching to the network?

Could this be a insufficient current problem?

Hi ,
We are using WP7xx module.
The scenario is as follows,

  1. Connect to the 4G network using airtel sim using WP7xx Module in one thread
    2.Keep communicating with RS485 port in onther thread.

After 3 minutes , the modem reboots without any clue.
Thanks in Advance.

you need to verify if TX or RX of RS485 makes this crash
Just TX continuously and no RX, will it crash?
Just RX and no output TX, will it crash?

Does this dependent on baud rate?

Also is your RS485 communication done in legato sandboxed application?

We are reading from the RS485 port and no writes are bring done.
We are using 115200 baudrate, I will check with other baudrates as well.I will get back to you soon on this.

Below are the AT commands we are using to communicate with the modem,
#define RTR_MDL “AT+GMM\r\0”
#define RTR_MFN “AT+GMI\r\0”
#define RTR_SN “AT+GSN\r\0”
#define RTR_FWV “AT+GMR\r\0”
#define RTR_CSQ “AT+CSQ\r\0”
#define RTR_PA_TMP “AT!PATEMP?\r\0”
#define RTR_PC_TMP “AT!PCTEMP?\r\0”

#define RTR_SIM_SPN “AT+CSPN\r\0”
#define RTR_SIM_CCID “AT+CCID\r\0”
#define RTR_SIM_IMSI “AT+CIMI\r\0”
#define RTR_GET_RAT “AT!GETRAT?\r\0”
#define RTR_TTY_SET “ATE1\r\0”
#define RTR_KSREP “AT+KSREP=1\r\0”
#define RTR_QRY_KSREP “AT+KSREP?\r\0”


Are you using uart1 for rs485 communication?
Did you enable hardware flow control?

Are you using legato app?

We are accessing RS485 port outside the legato. Our application doesnot use legato framework.
yes we are using port1 which is UART1(port number starts from port 0).
no_flow_control is being used.


could it be your program actually has problem?

The legato application has sandboxed function, you can port to legato app and retry