[Nut-upsuser] Unitek UPS 1250xD - megatec_usb driver

[Arjen de Korte]

[...]

> Asking for UPS status [Q1]...
> get_data_krauler: index [03], prefix [(]
> -> String: UPS No Ack (len = 10/128)
> get_data_krauler: retry [UPS No Ack]
> -> String: UPS No Ack (len = 10/128)
> get_data_krauler: retry [UPS No Ack]
> - Unable to fetch string 3
> get_data_krauler: connection failure
> Q1 => FAILED [timeout]

The above is the source of the problems. The first two attempts fail
internally in the UPS (since it reports 'UPS No Ack', which is an
indication that the USB controller in the UPS can't read the status).
Unfortunately, on the third attempt, the USB connection times out which
seems to be handled rather ungracefully.

The best solution would probably to ignore the first couple of failures in
the 'megatec.c' driver, before declaring data stale. Generally speaking,
one should be careful to declare data stale and only do so after a couple
of attempts to read the status (typically three in a row) have failed.

Best regards, Arjen
-- 
Eindhoven - The Netherlands
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