Multiple Propellers on same RS232?

T Chap

How would you configure a circuit to allow multiple Props to be downloaded at separate tmes from a single RS232?

Paul Baker

You would need to switch the reset line to the Propeller to be programmed. This could be done manually using a rotary switch or via logic level using a demux, there may be some issues with causing Propellers to reset when a switch occurs.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

Mike Green

If you put a protective series resistor in-line with pins 30 and 31, say 1K, you could wire all the pin 30's together and all the pin 31's together. If the bootloader is not running, these should be set to inputs and not affect each other. The reset lines would have to be switched so that the signal from the DTR level converter would only affect one Propeller. The only problem would be on power up when all the Propellers would come out of reset at about the same time. The series resistors would protect them from different signals on the pin 30s. With no response on pin 31 from the PC connection, all the Propellers would try to load from EEPROM which is probably what you want. As long as only one Propeller is running the bootloader at a time, only that Propeller will look at the PC connection for a download, thus the switched reset line.

T Chap

Thanks guys. Thinking out loud: take the unused RS232 pin 7 and pin 8, run them as CV's to some type of switchs at both PCB's, whether relays or logic switchs. Then, at some juntion near the computer, using two seperate physical buttons for A and B, the entire connection set is switched at each board as needed. Since the Props buth run daisy chained off the main computer's RS232 for programming, and ultimately BOTH have to be in the circuit to receive serial, two buttons will allow you to choose which is the one to be programmed, and after programming, put both back in the circuit.

This is getting more complicated I just realized, as both Props need to talk back to the PC! I think this will have to be changed to the most Remote(lesser important of two) Prop talks with the main Prop serially via RS232 and Full Dup Object, info needed back at the computer from the Remote will have to be que'd through the Main Prop. This appears to require a seperate Max3232 at each end, and a separate RS232 cable will have to run between Full Dup pins for Prop to Prop data.

Litefire

well, you wouldn't need the entire cable, just some wiring connecting the two pins on each prop.

and to avoid all these issues, why not just get a second Pc <-> prop connection (prop plug or USB2SER or equiv.) and configure it as a different COM port. that way you could send program 1 to prop 1 via com 1 (example numbers) and program 2 to prop 2 on com 2. then you could also open 2 terminal windows, each viewing a different com port, and have your communication that way.

~~Brian

Litefire

Unless the goal was to do it with one connection...

~~Brian

Dennis Ferron

I connected two Basic Stamp SX modules to the same RS-232 lines and it worked fine. When programming I only provided power to one or the other.