EM9191 not found in LattePanda3Delta m.2Bkey slot

IoT Modules
1

The EM9191 is not detected when installed in the m.2B slot of our LattePanda single board computer.
em9191-at-log on usb-c.txt (3.0 KB)

Please find the AT command log attached. This output was captured on the lattepanda sbc, using the Sierra dev kit with EM9191 installed, connected using USB-C cable that came with the dev kit.

the firmware in the EM9191 is AT&T SWIX55C_03.10.07.00 030.059_001

  1. Using Sierra dev board with installed EM9191 and connecting to our LattePanda SBC using USB-C cable provided with Sierra dev kit, the modem is recognized by ubuntu and works as a network adapter to go online, including to browse web sites.

  2. Using USB-C connection:

  3. “mmcli -L” successfully reports the modem information

  4. “nmcli” operations also work ok

  5. Two serial ports are seen in /dev: ttyUSB0 and ttyUSB1

  6. ttyUSB port works ok with the AT commands

  7. Have compiled and installed “Sierra Wireless USB Drivers” using “MBPL_DRIVERS_R32_ENG2-usb-src” following instructions in readme.txt. Both compile and installation seemed to work ok.

  8. Using m.2Bkey slot of LattePanda:

  9. “mmcli -L” reports “no modems were found”

Since the modem seems ok for USB-C cable use, are there any firmware settings in the EM9191 that I need to modify to enable m.2 operation?

2

did you check PCIE_DIS signal?

3

Thank you for helping!
It seems the pin 20 on lattepanda 3 delta m.2 Bkey slot is open (NC).

We made a voltage divider with
pullup
two 10k resistors between 3.3V and GND, to give us a pullup voltage of 1.65V. We wired (soldered) this pull up voltage to the pin 20.

“mmcli -L” still reports “No modems were found”
Is the Pin 20 tolerant of 3.3V? Perhaps 1.65V is not enough?

What can we try next?

4

Here is some information for the lattepanda 3 delta SBC m2. b slot:
From Specification - Documentation
“M.2 Key B(2242/2252/2280): SATA III, USB2.0, USB3.0, SIM”

Also, I have tried both with and without the SIM card installed in the SIM slot on the lattepanda3d.

5

How about pin 22?

Maybe you need to compare pin to pin voltage with the devkit

6

We also tried a wide variety of adapter boards with no luck. EM9191 still works great in the Sierra DevKit board. Tried adding pullup to 1.8V on the adapter boards too. I measured the various signals and have not yet found the issue. I have built a schematic using the devkit manual schematic.

Do you have any more suggestions?

Is there a reference design package to make our own PCB?

7

pin 20 → high (1.8V)
pin 22 → high (1.8V)

check pin 28 for power loss acknowledge
pin 24, pin 68, pin 38 → VCC (3.3V)

You might need to contact distributor for a schematic review

Btw, other user can make it work in m.2 adaptor: