Two ESP8266 with single GSM module

Hi All,

I want to use two ESP8266 (NodeMCU) with one GSM module (SIM800I).

Both the NodeMCU does different type of activity and and using the SMS I want to read data from both the NodeMCU.

Right now, I am able to do that with single NodeMCU and SIM800I.

How can I send the serial coming in from SIM800I to both the NodeMCU at a time? I read about serialpassthrough, but I have a doubt that it just passes the serial data but will not read it in the same NodeMCU. Am I correct?

Thanks in Advance.

@bencyp, your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for problems with your project :wink: See About the Installation & Troubleshooting category.

It's not quite clear to me if you want to send SMSes from both NodeMCUs or receive he same SMS on both NodeMCUs.

If the latter, below is one way that might work.

Decide which NodeMCU will control the GSM; that one will issue the commands. The second one will only listen on the serial interface and not issue commands to the GSM (do not connect the TX line of it, only the RX).

Another way is to let one NodeMCU communicate with the other one; and only one will communicate with the GSM. I'm not familiar with ESP8266 so can't tell you which options there are; another serial port, I2C, SPI, ...

First serves the modem with its own messages, the second tells the first to add extra messages.

Not too hard, but you have to handle the possibility for both wanting to send a message while modem is already busy.

A FIFO queue for outbound messages is the way to go…

Hi, @bencyp
Welcome to the forum.

Why 2 x 8266's?
What is your project?

Thanks.. Tom.. :smiley: :+1: :coffee: :australia:

There are tasks that the first NodeMCU is busy and I can't use the same to do more tasks.
I am trying to monitor the DataCenter that includes, Temp, humidity, door status Power status, Rodent detector, Water leak detection. All this is sent to Telegram Bot by 1 NodeMCU.

I have another Node MCU that will monitor the ISP links (4 of them). This is where the NodeMCU is taking time to send the Ping and wait for the response and calculate the latency. it is taking roughly 1 to 2 Sec to do all this without any delay in the code. So, if anything is wrong from both the NodeMCU I want to send out SMS or call or Telegram messages.

Anyhow, I have changed it to ESP32 and used both the cores to do these two main tasks.

Thanks for all the help

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