Hi, everyone!
I’m testing out the relatively new board+enclosure from rework.network called the M2-USB3 or QHM2U that is capable of sending 20W of power to the 5G modem and has an internal slide switch that does something with the pins in order to set the mode for the Sierra Wireless EM9190 and EM9191.
Anyway, since I am using a Quectel RM520N-GLAA, I need to know which way the switch should be set to properly support it.
I tried messaging the seller but they never responded. From the one video they have on YouTube it looks like the switch is set towards the back (the side with the SIM card slot, microUSB port, and DC barrel jack), BUT that video features the EM9190 and not a RM520N. The text description from the webpage says that this box supports the Quectel RM500U-CN.
I ASSume that I should put the switch in the other direction for the RM520N, but assumptions could fry something, so I am asking here if anyone knows which way the switch should go for Quectel 5G modems.
Not sure if I can post links here yet, so I won’t. The box is pretty easy to find on the rework.network website.
I am going to try to attach the stock photo of the board with the switch near the top edge of the photo. The back of the unit is to the left. The front of the unit, where the four antennae ports are, is to the right.
I hope this test goes well–I was getting pretty good results with an earlier model that has an RJ45 port and supplies 10W of power (not enough, based on the hardware design guide for the RM520N)
Thanks in advance!
Doing some testing with a multimeter, it may not matter in my case because it seems the slide switch is broken.
- If I put the multimeter in continuity mode and test pins 2 (common) and 3 (that goes to pin 20 on the M.2 slot), no continuity when the switch is supposed to short pins 2 and 3 (slide is to the left when pointing up as in the photo). Pins 2 (common) and 1 also do not short if the slide is slid to the right.
This fits the next test:
- If I put the multimeter in voltage mode, I can measure 1.8V on pin 2 (common), but the 1.8V never shows up on pin 1 if the slide is pushed to the right or on pin 3 if the slide is pushed to the left. So there appears to be no continuity within the switch here either.
Also,
- If I measure the voltage on pin 20 on the M.2 slot, it is never 1.8V in either of the switch’s two positions.
As such, the RM520N-GLAA is never affected by the switch’s position, as the switch in my unit appears to be broken.
The switch happens to be an ALPS SSSS811101, so I might replace it someday if I ever want to buy a Sierra Wireless EM91XX, but I probably won’t.
Just confirmed that the switch was broken in my unit. I was able to fix it by reflowing the solder and pushing it down towards the PCB while resoldering the four ground pins. Doing this mechanically squeezes the slider tighter inside the switch body.
Anyway, I have confirmed that the proper function of the switch is as follows:
When the slide is pushed towards the back of the board (where the microUSB port and SIM card slot are), 1.8V (High) is sent to pin 20 on the M.2 slot (PCIE_DIS[able]), which enables USB mode for Sierra Wireless EM91XX modems.
While the switch was broken, the RM520N-GLAA would have worked properly with the switch slid to either position. Now, with the switch fixed, it should be slid to the front of the board (the side with the M.2 slot) to work with Quectel modems.
