[WooreeINFO] JVM Porting ONLY with AT Commands for Cellular Modem Interface (with no support for PPP mode)

MicroEJ SDK
1

Dear MicroEJ,

We might face a case of porting Java VM for the device, which is connected to Internet over a cellular modem. And i found two different ways in principle for the MCU-to-modem interface, 1) AT Commands ONLY mode and 2) PPP mode, in the URL below.

https://os.mbed.com/docs/mbed-os/v5.12/apis/cellular-api.html

i can imagine mostly the PPP mode could be the case you are to port your Java VM, however my questions here are as:

a) Have you ever experienced the JVM porting work ONLY with AT Commands for the cellular modem interface?

b) If you answered yes above, how much would be the impact to the development lead time - compared to the PPP mode?

Thanks much in advance for your feedback.

Regards
YH Kwon

2

Dear YH Kwon,

We have some customer projects that uses AT commands to connect our Net APIs directly to the Modem. From my knowledge, we don’t have any customer using PPP mode.

Theoreticaly you could Map any low level net stack to the JVM (you can have a look at the chapter Networking in the device developer guide).

Regards,

3

Dear Pierre Rivron,

Thanks for your feedback first of all, however please be advised that what i have meant with was things as:

there would be no tcp/ip stack at the MCU where your Java VM is loaded.
the tcp/ip stack is only at the cellular modem.

Could you please update your feedback based on the above?

Thanks again.
YH Kwon

4

To use the net pack from the java application, you need to map the Low level apis to your hardware. The mapping is done at the MCU level but you can send AT commands from here directly to the GSM module.

5

Dear Pierre Rivron,

Thanks again for your additional feedback first of all, and do you think it would be OK if i understand like the below?

In case of porting MicroEJ Java VM with no TCP/IP stack in the MCU, like <Cortex-M4 + RTOS>, which connects to the network over a cellular modem by way of a serial connection using AT Commands;

“there would be NO big impact to the development lead time.”

Regards
YH Kwon

6

Dear YH,
To clarify: The NET (network) library in a MicroEJ platform requires a native ( C code ) driver implementation. The NET library drivers could be either be:

  • a TCP/IP stack running on the MCU
    or
  • a modem connected to the MCU (the MCU running the AT commands framework)
    If you already have a working AT commands software in C code running and validated, it will help to write this driver and reduce the development time.

Kind regards,
Stephane.