can i send data to PIC RX1 & PIC RX2 from my PC using two COM ports.

Rezer RS485 is a solution of what i have asked but its emplementation required 6 No. of IC's for a fully functional debugging of data on a single COM port.

I need a simple low cost less circuitry CIRCUIT, so that i will easliy add it up to my all serial port related projects.

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ash

 

Ash;

I told you it was more complex then first impressions

It's a little difficult to just draw you a design as one could use more details about the application and use. I assume this is for testing and troubleshooting the design and not required for the final product?

If it's just for testing then you need to define if you can utilize a PC with two comm ports or can you have two PC systems available for the testing period? Having two PC would make the testing session a little more straight forward as you won't have to figure out which instance of hyper terminal is active and which COMM port is monitoring which of the two PIC data lines.

If you have only one PC with one COMM port then you have the problem of output data from the PC. How will you determine which PIC signal input will receive the data from the PC, #1 pic, #2 pic or both at the same time without some kind of manual switching function?

Also can the two PICs be sending data to each other at the same time or will data only be sent in one direction at any specific time (half-duplex or full duplex)? If full duplex then you will defenitly need two COMM ports or two computers to do the monitoring as ORing two PIC data streams with one COMM input port will garble data if the two PICs send data at the same time.

The ORing logic needs to be performed on the TTL side of the max232converter(s) of course. If I recall the RS-232/TTL converters utilize a negative logic such that when no data is being send (steady mark condition) the TTL level is at a high state. If that is fact then the ORing function can be performed using a 2 input AND gate (74LS08 should work). If the serial logic level is using positive logic (steady mark condition = TTL high state) then a 74LS32 OR gate would perform the proper function. Each 74LS08 (or 32) has four gate functions avalible.

This ORing function gate would be used where ever you want to have two TTL output pins sending to one TTL input pin. How many Oring function you need again depends on the number of COMM ports or computers you have avalible for testing.

Lefty

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Measurement changes behavior

 

On a PC with two serial ports, the easiest solution I can see is to write a program that relays the signals. I.E. what comes in com1 goes out com2 and vice versa. It would then be very simple to monitor what is passing back and forward and inject additional data as necessary. There will be a latency of 1 byte between the pics but I can't see any other way to do this without external circuitry.

Mike.

 

Might be fun to daisy chain the serial ports, you'll have to echo the data though.
So TX1 to RX2, TX2 to RX3, TX3 to RX1
Puddles of fun.

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

 

It's a little difficult to just draw you a design as one could use more details about the application and use. I assume this is for testing and troubleshooting the design and not required for the final product?

Yes it is for testing and trouble shooting the design

If it's just for testing then you need to define if you can utilize a PC with two comm ports or can you have two PC systems available for the testing period? Having two PC would make the testing session a little more straight forward as you won't have to figure out which instance of hyper terminal is active and which COMM port is monitoring which of the two PIC data lines.

Only one PC & one COM port is available.

If you have only one PC with one COMM port then you have the problem of output data from the PC. How will you determine which PIC signal input will receive the data from the PC, #1 pic, #2 pic or both at the same time without some kind of manual switching function?

#1 PIC & #2 PIC response command can be different. For exampl #1 PIC respond on YES & #2 PIC respond on NO only. This can be done in programming.

Also can the two PICs be sending data to each other at the same time or will data only be sent in one direction at any specific time (half-duplex or full duplex)? If full duplex then you will defenitly need two COMM ports or two computers to do the monitoring as ORing two PIC data streams with one COMM input port will garble data if the two PICs send data at the same time.

Yes we will receive garbage data when both PICs send data at a time but this can be fixed by proper time slicing.

The ORing logic needs to be performed on the TTL side of the max232converter(s) of course. If I recall the RS-232/TTL converters utilize a negative logic such that when no data is being send (steady mark condition) the TTL level is at a high state. If that is fact then the ORing function can be performed using a 2 input AND gate (74LS08 should work). If the serial logic level is using positive logic (steady mark condition = TTL high state) then a 74LS32 OR gate would perform the proper function. Each 74LS08 (or 32) has four gate functions avalible.

This ORing function gate would be used where ever you want to have two TTL output pins sending to one TTL input pin. How many Oring function you need again depends on the number of COMM ports or computers you have avalible for testing.

Need a schematic diagram to elaborate it practically

__________________
ash

 

Tell you what, why don't you draw something up and post it and we can then tell you if it will work properly or not It's is in fact your project.

Lefty

__________________
Measurement changes behavior

 

I did something like that once. The user needed to have up to 4 boxes connected to the serial port on a workstation. I used a RS232 based network with addressed packets.

On powerup boxes were setup not to pass packets to the next box. That allowed the workstation to talk to the first box and assign it an address. Then turn on the connection to the next box and assign it an address. The boxes did not speak unless spoken to so the workstation needed to poll periodically.

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Sorry & thanks

Let me do it myself

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ash

 

Nobody's giving up here. This is a help forum. But you need to help us, help you. We're not mind readers and it is hard at times visualizing someone elses visualization of what they want (That means your not in the design stage yet). It would help if you at least had a visual representation of what you want, and post it. We're more than willing, but you have to be as patient as we've been with you.

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"Remember, you're special.....just like everyone else."

 

You are right rezer. We all are here to help each other.
I always wish all of you to help me technically.
Sorry for the unprofessional attitute, specially from Lefty

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ash