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Re: [lwip-users] hayes commands popping up in ppp stream

From: chrysn
Subject: Re: [lwip-users] hayes commands popping up in ppp stream
Date: Fri, 14 Nov 2014 17:43:47 +0100
User-agent: Mutt/1.5.23 (2014-03-12)

hello sergio,

thank you for your responses.

On Fri, Nov 14, 2014 at 10:06:00AM -0300, Sergio R. Caprile wrote:
> Since PPP expects a serial transparent interface, and you are not
> providing that, I would write a "tap" which provides that to PPP and
> "taps" all other data out.
> GSM modem ----> real serial --> my module -----> PPP virtual serial
>                                     -----------> tracking virtual serial
> Some GSM modems provide a packetization interface to clearly separate
> muxed channels on the same serial interface. If yours does not, you'll
> have to work harder.

that is what i'm about to implement right now. unless the ascii jabber
inbetween contains 0x7e 0xff sequences, that should be doable with
reasonable effort.

On Fri, Nov 14, 2014 at 10:11:01AM -0300, Sergio R. Caprile wrote:
> BTW, 
> is a clear indication that your power supply is not well designed and/or
> your module is not well decoupled.
> It needs >2A current to transmit for a very short time, you need a 100uF
> low impedance
> in parallel with 2uF MLCC close to the module; or better, what the
> hardware manual recommends.

i was afraid so when i first saw them, but i never ran into an
UNDER-VOLTAGE POWER DOWN condition so far; thing is, i'm running my
entire board off 3.3V, which is the threshold for the warning. the
module can do down to 3.2V, and a 2m2 cap in parallel with a 4u7 and
100n make sure it won't even if the usb power supply doesn't handle
bursts well.

i hope it's sufficient -- or are you confident that this is indication
of trouble even when running on 3v3?

> Sorry about that, but I used to work with the tech support for Simcom in
> Argentina...

honestly, i wasn't aware that such a thing exists; when it comes to
support, nothing the simcom website has looks like you'll ever talk to a
technician. could you point me to where i can reach their (possibly
local, paid if needed) tech support?

best regard

Most people would leave. Not us. We're Vikings. We have stubbornness
  -- Hiccup, son of Stoic

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