Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Multiple uart with one microcontroller.

Status
Not open for further replies.

HIREN DAVE

New Member
Hello,

I want to connect 8 GSM modems with 1 microcontroller. but my microcontroller has only one UART. So i need multiple UART. which are the techniques? is there any direct IC available?
 
What kind of gsm modems?
What kind of microcontroller?
How long is the communication distance?

- You could use an IC like MAX14830. "Quad Serial UART with 128-Word FIFOs". This is not a cheap IC.
- Or, You could use small microcontrollers to communicate with each gsm modem and then connect them to a main micrcocontroller using i2c or spi. Not sure if this is cheaper solution than the MAX14830, depends what microcontrollers you use.
- Or.. maybe some kind of wireless link that can multiplex.. zigbee or bluetooth.
- Or, buy a microcontroller with enough UARTS.. I think 4 uarts is the maximum you can find, so you could buy two of those and make them communicate with each other via i2c or SPI.

But, there might bee even easier solution.. depending on what kind of GSM modules you have. Maybe there is an interface that you can use.

PS. Why do you need so many GSM modems?
 
Last edited:
For example atxmega 128a3u has 7 uarts.
If you need to talk only with one device at a time, then you could use some multiplexer to connect all those devices.
 
For example atxmega 128a3u has 7 uarts.

Good point. That is a cheap uC also. Under 5 dollars. But, not an easy one to use for a beginner. Especially if Hiren is used to use PICs.
7 peripheral USARTs and one software USART would be very doable.

If you need to talk only with one device at a time, then you could use some multiplexer to connect all those devices.

That is a good point also. What kind of communication do you expect to have with the devices?
 
does price matter? some the cheapish pics have 2 uarts 4 slaves connected via spi to a master??? not an engineer way for sure but pretty easy to sort
 
I once managed 5 UARTs on a 68HC11 in the mid 90's using the on board UART and the TIC inputs on edge timed interrupts in software. Worked a treat at 9600 baud with small amounts of data from each UART like GSM SMS messages. However even on a 16MHz clock, it kept the CPU busy when fully loaded but it did manage to capture all messages and turn them into a IP type stream for passing on to another CPU.
These days I would use something based on a 16550 core with multiple UARTs on-chip as an external peripheral IC.
 
If you only need to talk/listed to one GSM modem at a time, then a multiplex/demultiplex scheme would probably be easiest. You will need three uC pins to select which modem you are talking to at a.

I would start with a pair of 74HC4051. Since it is an analog switch it can work as both mux and demux. The unselected outputs on the demux will be hi-z, so you will need some pullup/down resisters on those lines to keep them from floating.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top