Closure on LE910 Problems

[Randy Yates]

Folks,

I am so thankful for all your help and quick responses for the past two
months or so. To show my thanks I wanted to feed back the solutions we
found to our problems back to the list.

1. USB Babble Interrupt (when wired ethernet was NOT connected) on LE910

Turns out this was a hardware problem completely unrelated to the LE910
or the processor. Our hardware engineer used a switching regulator (the
TI TPS63060) and had configured it for power-save mode. That regulator
goes in and out of power save mode when the load crosses about 100 mA.
It also produces some horrendous (and documented) voltage transitions
when transitioning. The ethernet PHY was drawing about 30 mA. In power
up conditions our average non-ethernet load current was 90 mA - close
enough to allow transient currents to transition the regulator in and
out of power-save mode, so we had huge voltage spikes without the
ethernet plugged in. Plugging in the ethernet got us up to 120 mA which
was sufficient to avoid most of the transitions.

2. Connection Issues at Certain Cell Sites

This problem was due to a confluence of using an unsupported Telit
module, the LE910-NVG, which was intended for Verizon, and an AT&T SIM.
It appears these sites were trying to force us into LTE mode and that
combination only worked with GSM/GPRS and WCDMA. Issuing a AT_WS46=29
fixed it since that limits the allowed connections to GSM/GPRS and
WCDMA.

Thanks again for everyone's help.
-- 
Randy Yates, DSP/Embedded Firmware Developer
Digital Signal Labs
http://www.digitalsignallabs.com