[arm-allstar] TX time out

[Doug Crompton]

Matt,

 The best thing to do is understand why it happened. Most of the time it is because you turned off a radio while you were connected. If the radio is using carrierfrom=usb in simpleusb.conf it means that COS is valid when it is at a high level. COS valid is telling Allstar there is a local signal present and keys up all other connected nodes. If the radio is turned off or disconnected from the interface there is a pullup resistor in the cm108/cm119 chip that pulls the COS line high and tells Allstar there is a valid COS signal when there really is not. So you should never do that with Allstar. Either disconnect all nodes or shut Allstar down before turning off or disconnecting a radio. This is a good practice in general.

That being said the new RPi - 1.02 - code when run in beta mode as described in the readme file right after the download link has two commands to help deal with this situation.  They are -

rx_timeout=300000
                                ; Timeout on hardware COS. Used to avoid hangup
                                ; of circuits with COS lockup.
rx_cosflap=20
                                ; Minimum COS Timeout reset period. Used to
                                ; avoid resseting of rx_timeout with a flapping
                                ; squelch.

The important one here is rx_timeout. You have to actually add these commands to the rpt.conf file to change the values otherwise they assume the defaults shown above. 

rx_timeout is the timeout on COS which comes from your node radio receiver. I know this is confusing because values are defined based on the node transceiver. You said tx_timeout but it is really rx_timeout - the tx signal that comes from you transmitting to the node receiver. The default is 300000 ms or 5 minutes. This is the amount of time COS can be held valid until it times out and releases the COS signal. To reset the COS line must go invalid. The 5 minutes default is probably a little long in most situations and probably set to 3 or 3.5 minutes would be a better choice.

All future versions of our code will have these commands built-in and operational from start. The parameters you see above will be in each node definition. This is a per node definition so multiple nodes on a server could each have different values. So out of the box no node will be able to lock up a circuit for more than 5 minutes unless you set it shorter or longer.

Users should also set a true TX timeout in their transmitters or transceivers where possible to protect the TX. So if a hangup like this happens the worse case scenario is transmitters on the circuit timing out until it is cleared.

73 Doug
WA3DSP
http://www.crompton.com/hamradio


> Date: Fri, 26 Aug 2016 19:57:32 +0100
> To: arm-allstar at hamvoip.org
> Subject: [arm-allstar] TX time out
> From: arm-allstar at hamvoip.org
> CC: matt at m0lmk.co.uk
> 
> Hi all.
> 
> My node got booted off from one of the allstar hubs today because it was 
> stuck in constant TX. Is there a setting to prevent this?
> 
> Thanks,
> 
> Matt
> M0LMK
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