I have a BG95-M3 PCB module an ESP32 dev kit and a CH341A programmer. The CH341A works with 5v, so I’m using a simple transistor-based logic converter that I bought recently. I want to communicate to B95 via main UART but it isn’t working, I can’t obtain any data from UART, am I doing something wrong? When I try to use ESP32 it repeats the same behavior. No response.
My BG95-M3 PCB module
My arrangement with CH341A programmer and the logic converter
The connection
Hello @Parrot02
well, VDD-EXT is an output of the modem to provide power for the level-shifter. You still need to actually power the modem via VIN or VBAT (and possibly power it on via PWRKEY). I suggest you consult the BG95 Hardware Design document.
Thanks
Felix
I’m sorry that I didn’t put the VIN there but I’m giving 5v to the VIN pin, except the PWRKEY, it’s the only pin I’m not using. But the net led still works without it
Hello @Parrot02
ok, I see. Yes, I’d agree, when the net led blinks the modem is running.
Have you tried to change the serial baudrate. I believe by default it should be 115200, but I could be wrong.
Thanks
Felix
I also tried 9600 but no response. This is my second module, the first one was damaged because I tried the CH341A directly without the logic converter and broke the module. So, I don’t want to do it again, I bought another logic converter so I’m waiting deliver.
Hello @Parrot02
FYI: my BG95 upon startup automatically sends RDY and then APP RDY via UART using 115200 baud.
Thanks
Felix
How your wiring look like?
What voltages are you shifting between? And are you using the bg95 chip or mini-pcie?
I had this issue while trying to shift from 3.3V (my microcontroller) to 1.8V for the bg95. I was using the mini-pcie version which apparently has a 3.3V logic converter already built in.
I’m using this dev module I don’t think it has a built-in level shifter because I measured 1.8v in MAIN-TXD pin. The CH341A works with 5v but I’m still having the same problem with ESP32 that works with 3.3v.
I have a few questions:
-What logic level converter are you using?
-To make sure, you are trying to communicate with he BG95 via the CH341A right?
-Have you checked the voltages at the logic converted to make sure they are 1.8V and 5V?
A lot of logic level converters also require you to make sure that you power on the low-side before the high side.
I’m using this logic converter here but I already tried this one . When I measure the voltages between the pins it’s right on both sides, 1.8v low side, 5v high side.
