--- In "camel85kv" <> wrote:
>
> Hello,
>
> I have a little problem that I can't seem to figure out. When I
try to connect my TS-7400 to
> the internet via a Novatel U720 EVDO modem, the system hangs. No
serial console, no
> ssh. I think it's related to the power supply, since this modem
sucks so much juice that it
> ships with a Y-cable so it can draw power from two USB ports. I
have it connected to my
> TS-7400 via an unpowered USB hub.
This Y-cable should not be necessary on the TS-7400. One port will
provide just as much 5V power as 2 ports-- there is no individual
port current limiting on the 7400 USB ports.
The cellular modem hardware devices do draw huge amounts of pulsed
current. Typically, cell applications have a battery-based power
supply which are capable of handling these power requirements, but
wreaks havoc for small embedded power-supplies-- even though average
power is low, instantaneous power requires overdesign.
>
> I saw that someone else on the forum was having power issues using
a GSM modem on
> the TS-7200 series boards. Aparently that was solved by using a
jumper to bypass the
> onboard voltage regulator.
Could this have perhaps been a TS-7260? There is a 5V regulator that
can be disabled on that board if the power coming in is known-good
5V, all other boards (including the 7400) pretty much connect the
external 5V to the USB ports so power supplied via USB is primarily
correlated to the external power supply capabilities.
> The TS-7400 doesn't have that as far as I can tell. I'm using
> the stock 5v, 1A (regulated I assume) power supply that comes with
the development kit.
Yes, these are mini switching regulated power supplies. (not to be
confused with el-cheapo wall-wart transformers) You might try using
a bigger one. We have 3A 5V supplies available also but I might
suggest trying a good bench supply if you have one.
> Power supply voltage is around 4.70 volts with everything plugged
in and at a prompt.
> When I try to bring up the modem, the voltage drops to about 4.53.
Is that low enough to
> cause the board to hang?
Are you measuring this on a multimeter or a high-speed scope? It may
be dipping a lot lower than that for uS/mS after power is enabled,
which is bad. However, there is a reset chip on the 3.3V regulator
that should catch these power dips and reset the board (not lock
up). When it locks up, does it immediately reboot if you unplug the
USB device?
>
> It looks like pppd connects ok, but I'm not sure what is going on
after that. It crashes on
> the command "pppd call sprint", where "/etc/ppp/peers/sprint"
contains my ppp settings
> for a Sprint mobile broadband account. For reference, "lsmod"
includes all of the modules
> I thought would be necessary for this ppp connection: ppp_synctty,
ppp_async,
> ppp_generic, slhc, usbserial. The pppd log dump is listed below (I
had to fetch the log
> after rebooting since it crashes every time). Any thoughts on what
might be causing the
> crash?
This may still be a software driver problem or USB device problem.
I'd suggest trying a powered USB hub and see if the behavior
continues. Also, a good test sometimes is to see just how "locked
up" the board really is--i.e. if you can still ping the ethernet
iface the CPU is probably still running perfectly fine and Linux is
at least running IRQ handlers.
//Jesse Off
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