SSR-1U User’s Manual
Rev -, 27 Dec 2019
© 2019 Slerj, LLC
20
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configuration data, so all channels operate at 115200 baud, 8 bits, no parity, and 1 stop bit for
capture.
The process for capture involves presentation of the boot loader message at startup, the user
quickly typing the string
config
, the device replying with an upper case, four character challenge
string, and the user echoing the challenge string back to the device in lower case. Details are as
follows:
On startup, the SSR-1U displays the boot loader message and device information.
An 800ms window begins in which a valid character of the capture sequence must be
received from the user. If an invalid character is received, or 800ms elapses, the capture
sequence is aborted and the device boots normally according to its stored configuration.
Each valid character received resets the capture window to 800ms. Since it is difficult to
judge the time from power on until the device is ready to begin receiving the capture
sequence, the valid capture sequence includes up to 5 lower case
z
characters prior to the
string
config
. A typical capture will involve hitting
z
while powering on the device until
the
z
character is echoed from the device, then typing
config
.
When the previous step has been completed, the SSR-1U will send a random challenge
string consisting of 4 upper case characters, and a new capture window of 5 seconds is
established. The user must type those same characters in lower case to complete the
capture process. If the challenge string is not answered in 5 seconds, the capture process
is aborted and the SSR-1U starts normally.
In order to support the capture feature, a distinction is made between the active function of a
channel and its configured function. The active function will mirror the configured function
when possible. Once the shell becomes the active function on a channel, the parameters that
affect communication (baud, bits, parity, stop, and active function) are fixed until reset. Any
channel configuration options changed for the captured channel (and saved) will not take effect
until the next reset. If
shell
was the configured function on a channel other than the captured
channel, the active function for that channel becomes
disabled
.