LM048: Common Issues

Problem 1

I am able to connect to LM048/LM058 Serial Adapter, but no communication is happening?

or

I am able to connect to LM048/LM058 Serial Adapter, but communication data is garbled/garbage/incomprehensible?

Solution

There can be multiple reasons why you are unable to able to communicate with LM048/LM058

• The serial settings on LM048/LM058 should always match with the host device to which they are connected. For example, if the host is a label printer configured at 9600 8 N 1, flow none setting, then the LM048/LM058 should also be configured to the same serial settings. If this is not the case then user may see garbage characters printed out on the printer
• If you have checked point 1 and still don’t see any communication then the slide switch position (DTE/DCE switch) on the LM048 is incorrect. Please change the slide switch position and see if it fixes the problem. As a guide, when LM048 is connected to a PC with NULL Modem / Cross Serial Cable, the slide switch should be at DTE position. When the LM048 is connected with a straight serial cable, then slide switch position should be at DCE position
• Check that the COM port number is correct if you are using USB-RS232 converter. This information can be checked in the Device Manager

If none of the above work, please raise a support ticket with us and we will help you fix the problem.

Problem 2

I am unable to connect to LM048. What is the reason and how to fix this problem?

Solution

There can be multiple reasons why you are unable to connect to LM048 which are listed below

• LM048 is configured as master. In Master mode LM048 will reject any incoming connections
• Bonding address is not null. When bonding address is set and LM048 is slave, LM048 will reject connections from any device except the bonded address. In master mode, LM048 doesn’t accept incoming connection anyways.
• Pin code on LM048 is not matching with the one user entered.
• Pin code authentication disabled on LM048 end while it is enabled on the remote end or vice versa

If you read the LM048 Settings via LM149 Software, make sure role is slave and bonded address is null as in the screenshot below.

Problem 3

LM149 Configuration Software is unable to read settings from LM048/LM058 Serial Adapter?

Solution

There can be multiple reasons why you LM149 Software is unable to read settings from LM048/LM058

• The chosen COM port number is incorrect. Please check the device manager for the correct COM port number especially if you are using USB-RS232 converter.
• The LM048 is in connected state, BLUE LED is ON in connected state. If the LM048 is in connected, LM149 Software is unable to read settings. Please make sure the Blue LED is blinking or OFF when LM149 reads settings from the LM048 Adapter.
• The slide switch is in the wrong position. If LM149 fails to read settings, please change the slide switch position and try again
• Serial Port connection is loose. Please check the serial cable is plugged in properly to the PC

If none of the above work, please raise a support ticket with us and we will help you fix the problem.

LM149 Software tries to communicate with the LM048/LM058 Serial Adapter at the selected COM port settings. If the adapter is unable to communicate at the settings, then the LM149 Software tries combination of all different baud rate, parity, stop bits and flow control settings until it finds the correct settings as programmed on the LM048 Serial Adapter. It may take LM149 Software around 2 mins to try out all the serial settings

Problem 4

I am using a Serial Terminal program to communicate with LM048 Serial Adapter. When I send AT Commands to the LM048, I get OK response for the first command but ERROR response for all subsequent commands. What is the reason for this?

Solution 1

Since you are getting a response for the first AT Command, it means the slide switch position on LM048 and serial settings on serial terminal are correct. The reason why you may be getting OK response for the first AT Command and ERRORresponse for subsequent commands is because the End of Line Setting on the serial terminal is set to CRLF (Carriage Return Line Feed) instead of CR (Carriage Return).

The LM AT command firmware uses carriage return (CR) as the command delimiter. So when you send a AT command it goes in the UART buffer as AT\r\n. AT\r is processed by the firmware while \n is left in the UART buffer. Next time when you send another AT Command like AT+VER, the actual command received by the firmware is \nAT+VER\r\n. The firmware treats the command \nAT+VER\r as ERROR and hence returns ERROR response to the user.

So make sure the EOL setting is set to CR in your serial terminal as shown in the diagram below.

If you are still facing issues, please raise a support ticket with us and we will help you fix the problem.

Solution 2

Second reason why you are getting OK response for AT command but ERROR for any other command is because the COM port you are communicating is the internal modem of the Laptop or Desktop. Internal Modem show up as COM ports in the device Manager. When user opens this modem COM port it will respond to some GSM AT Commands like AT, ATI0 but may give ERROR response for other commands.

To resolve this issue, make sure the correct COM port is used. Check Device Manager for the correct COM port number.

 

If you are still facing issues, please raise a support ticket with us and we will help you fix the problem.

Solution 3

The third reason why you are getting OK response for AT command but ERROR for any other command is because the LM048 you are using is running old firmware version v4.22 or RACv1.03. A quick way to check if this is the reason, send ATI0command and response should be either Fw Version 4.22 or Fw Version RACv1.03.

If this is the case, then please refer to LM048 v4.22 AT Command Manual for complete list of RACv1.03 and v4.22 firmware commands. Alternatively you can also download and use LM049 Configuration Software which is a Windows GUI application for configuring adapters running v4.22 or RACv1.03 firmware.

If you are still facing issues, please raise a support ticket with us and we will help you fix the problem.

Problem 5

Is LM048/LM058 Serial Adapter compatible with Android Devices?

Solution

Yes, LM048 and LM058 Serial Adapters work with Android Devices. You could download some popular Bluetooth Terminal Applications from Google Play Store and try it out with LM048/LM058 Serial Adapter. We have tested various applications on Play Store with LM048 and LM058 Serial Adapters.

Some Android Bluetooth Applications are listed below

LM BT Terminal – This simple Bluetooth Terminal Application was developed by LM Technologies

Advanced Bluetooth Terminal

Blueterm

Problem 6

Is LM048/LM058 Serial Adapter compatible with Apple Devices (iPhone/iPad)?

Solution

No, LM048 and LM058 Serial Adapters currently do not work with Apple (iOS) Devices like iPhones and iPads. The reason is because Apple devices require any device or accessory interacting over Bluetooth to incorporate an Authentication Chip. LM048 doesn’t incorporate the Apple Authentication chip at the moment.

LM Technologies is currently working on incorporating the support of Apple Authentication processor with a special variant of LM048 Serial Adapter.

Please note: Apple Authentication Processor is not required for communication with Apple Mac. So LM048 works with Apple Mac

Problem 7

How do I use a LM048 or LM058 Serial Adapter with Bluetooth USB Adapter or in-built Bluetooth Controller of a PC or Laptop?

Solution

Please see LM048: How to use with Bluetooth USB Adapter

Problem 8

How does modem signal transfer work on LM048/LM058 Serial Adapter?

Solution

Please see LM048: Modem/RS232 Signal Handling

Problem 9

How to pair 2 LM048s so they auto-connect to each other on power up?

Solution

Please see LM048: How do I pair two LM048s to auto-connect to each other?