I am using a Banana-Pi R64 and using Quectel’s EC25 mini PCIe module for network connectivity . This module comes up as 4 USB ports when connected. I have set it up to choose the network automatically whether 2G, 3G or 4G. But when my network falls back to 2G, the 4 USB ports starts behaving weirdly. They keep attaching and detaching continuously. How do I solve this?
It seems to be power related problem. Looking at achematic of bpi r64 it use SY6280 switch to supply pcie devices. Limit resistor is set to 1.5A whitch is not enough for 2G network. I guess EC25 datasheet will tell that but from my experience modem can draw up to 2A in 2G. Solution: do not use 2G mode Or put at least 1000uF capacitor on pcie supply line Or Change Ilimit resistor to 3.4k but im not sure how this will affect main DC/DC.
Hi @niebieski20, I replaced the 4.7k to 3.3k resistor but the issue stayed.
In EC25 datasheet on page 21 it is mention that current draw can peak 2.7A.
Try place two or three low ESR 470uF capacitors close to mpci connector. Also if you have any other devices like sata drive or additional wifi card disconnect it and check again.
I do not have EC25 yet so cannot confirm that. I should have it in this week so can check.
sounds like power issue, you can verify that by enabling the SIM PIN, make sure you’re in a GSM coverage only zone, enter PIN using +CPIN command, I assume it doesn’t only disconnect but reset itself, or ? What are the exact symptoms ? /T.
Thank you @niebieski20. We tried observing voltage dips on VCC pin of MiniPCIe on DSO and found that the voltage almost dropped by more than 2V on 2G and that is when my Quectel module showed rebooting behaviour.
Add two or three 470uF thantal capacitors close to pcie connector. That should do the job. Check on DSO that voltage drop should be gone or much smaller