LimeNET Micro - using the GPS - No PLL Lock

Projects LimeNET
1

Hi!
I’ve been playing around with the LimeNET Micro I just received, and it works beautifully! I plan on installing osmo-nitb next week and playing around with a GSM base station.

In the meantime, I’ve tried the GNSS receiver. By plugging an external antenna, the LED5 turned to blinking green, indicating a lock (as per Hardware Description).

The NMEA data from the uBlox GPS can be retrieved on UART1 (/dev/ttyS0). After some fiddling around, I managed to enable the interface in /boot/config.txt (thanks to this post):

force_turbo=1
enable_uart=1
dtoverlay=uart1,txd1_pin=32,rxd1_pin=33

The NMEA data can then be read by typing:

stty -F /dev/ttyS0 ispeed 9600 && cat </dev/ttyS0

However, I’m still puzzled why LED3 is still blinking Red/Green, which according to the hardware specs, indicates an unlocked PLL. Does this mean the clock is still not synced to the GPS? Do I need to configure something else?

Thanks for your help!

2 Likes
2

Tagging @Zack.

3

Hi, same problem here. GNSS is locked (blinking green led 5) and the PLL should be tuned with the 1pps from GNSS (led4 solid orange) but led 3 shows an unlocked PLL (blinking red/green)

I have similar configurations in place for accessing the serial port.

Any idea?

4

@Zack, could you take a look, please.

5

Hi @M.dasilva,

LED3 indicates FPGA PLL status, used for LMS7002M digital interface. This PLL needs to be configured by the software to get lock.