On Wed, Jul 17, 2024 at 12:01 PM, Brian Webster N2KGC wrote:
The one drawback to TNC¡¯s being daisy chained together on a single serial port, is that in one of the TNC¡¯s stops working in the chain, ALL of the TNC¡¯s on that serial port stop working.
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Worth noting is that the speed of the serial port needs to be at least the sum of all the TNC¡¯s serial ports in the daisy chain. This would suggest that your serial port speed should be set to the same as your on air speed because if you had 4 TNC¡¯s in a chain where the serial speed was set to 9600 baud, the computer serial port would have to have a speed of 9600 x 4.
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Brian N2KGC
Yes I agree the "if one goes they all go" is a definite draw back with daisy chain topology.?
But, on the flip side if your running your node on Raspi you can now run a multi channel TNC system with nothing but the built in hardware(/dev/ttyAMA0) UART*.?
No more needing to mess with USB rs232 dongles or HAT's.? And the pi hardware UART can do at least 921,600 baud, so you could build quite a tall stack of TNC's even at 9600 radio speed :)?
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73
Chris K1MAL
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*The pi hardware UART is 3.3v on the GPIO pins. You need to use a max232 chip or breakout board from amazon/ebay to match the pi to the rs232 levels on the tnc.?
