I'm looking to use a small Local Area Network System using PIC16F628A's as the Slaves, (and for the rime being, also a master).
The overall distance from the Master to the last Slave would be about 25 Metres, and the Number of Slaves I want to link is around 30.
I want to use the direct connection method of Master Tx line to ALL the Slave Rx lines, and ALL the Slave Tx lines back to the Master Rx line.
I know I can achieve this over very short distances (bench testing, below 1 metre between about 6 units).
I have already designed and manufactured some 'Units' that were for 'stand alone' operation, but in anticipation of this, left the Tx / Rx lines of ALL the units.
I have been looking for info on the following, any info would be helpful !
1. How many Slave unit Rx pins can I connect to the Master Tx pin ?
2. Would I need to use an 'end of line' termination pull up resistor (100R/1K)?
3. Is there a 'limit' to the length of the connections etc.
I appreciate that the Baud Rate has an implication on this, I would like to use the 'inbuilt' USART function, I am using the 4Mhz internal clock, and would like to run 'as fast as possible', but the lowest (9.615 kbaud) would still be acceptable.
If this is still found to be 'too fast', I can use the Tx/Rx pins on ALL devices as I/O pins and program up a software USART to run more slowely.
I want to avoid adding any extra components if I can.
Any help / suggestions would be greatly appreciated.
Roy
The overall distance from the Master to the last Slave would be about 25 Metres, and the Number of Slaves I want to link is around 30.
I want to use the direct connection method of Master Tx line to ALL the Slave Rx lines, and ALL the Slave Tx lines back to the Master Rx line.
I know I can achieve this over very short distances (bench testing, below 1 metre between about 6 units).
I have already designed and manufactured some 'Units' that were for 'stand alone' operation, but in anticipation of this, left the Tx / Rx lines of ALL the units.
I have been looking for info on the following, any info would be helpful !
1. How many Slave unit Rx pins can I connect to the Master Tx pin ?
2. Would I need to use an 'end of line' termination pull up resistor (100R/1K)?
3. Is there a 'limit' to the length of the connections etc.
I appreciate that the Baud Rate has an implication on this, I would like to use the 'inbuilt' USART function, I am using the 4Mhz internal clock, and would like to run 'as fast as possible', but the lowest (9.615 kbaud) would still be acceptable.
If this is still found to be 'too fast', I can use the Tx/Rx pins on ALL devices as I/O pins and program up a software USART to run more slowely.
I want to avoid adding any extra components if I can.
Any help / suggestions would be greatly appreciated.
Roy