8051 serial communication with 2 devices

i would like to connect 2 devices like GSM, Zigbee, with one 8051 microcontroller. is it possible to connect with one 8051 are i need to provide separate microcontroller for each device. please provide me some technical explanations

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please provide us with money.

And please stop using last century microcontroller.

Bye Jack

Yoda of Borg am I! Assimilated shall you be! Futile resistance is, hmm?
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Which 8051? It's probably not an original intel MCS-51 device.

If you need a second serial connection (UART) it is possible to write one in software. It's actually a pretty good exercise and there are application notes that describe the process. One example is at . It's for a different processor but the technique is similar. Do note that your processor's instruction cycle time and interrupt latency will set the maximum achievable signal rate.

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Rich Webb

Look at the C8051 family from Silicon Labs. Many of them have 2 UARTs.

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Marc Guardiani

That's assuming that the devices are UART. My GSM is USB and my *Bee is SPI.

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Use a device with 2 UARTs, or include an RS422/485 interface in your design. Alternative, don't use and 8051 at all.

Regards, Richard.

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FreeRTOS info


A very late reply!!!

I'm chiming in because I'm doing some background research on the 8051. I wa s dismantling some APC UPS units for recycling purposes. I came across the monitoring interface - model AP9607 for those following at home. The card i s actually a complete computer system in itself: microcontroller, EPROM, an d I/O. It can technically function alone.

The microcontroller is a Siemens SABC510, which I've come to find out is a C510, which is a 8051 equivalent. I'm thinking about using this card as a c hallenge, to maybe turn it into a full-on computer with RAM and such.

Regarding this thread, the AP9607 actually has two serial interfaces. They' re used to monitor the UPS. Both interfaces are controlled by the C501, as there are no UARTs on this board. I've yet to disassemble the code in the E PROM - I'll do that to study how the serial interfaces are accessed.

With that, it sounds like the C501, and quite possibly other 8051 equivalen ts, can drive two serial interfaces. But I won't fully know until I finish studying the firmware.

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Bryan Villados


For my final-paper (now more then 20 years ago), I needed to let one controller-device talk to 4 slave-devices, using the onboard UART. FOr that, I used RS485 driver-ICs to provide a "bus" and wrote a small master-slave (or master-4slaves in this case) to control the communication.

I guess you can do this with any interface that provides some kind of "bus" (e.g. open collector).

The other option (as Bryan also mentioned) is to use a software-serial interface.

Cheerio! Kr. Bonne.

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