B-L072Z-LRWAN1 CN11 (USB Conn.) - Device mode

[Kostas Papouis]

Posted on May 01, 2018 at 16:05

Hi Everyone,

I would like to ask a question regarding to powering the B-L072Z-LRWAN1 direct from the CN11 USB connector.

The user manual of the B-L072Z-LRWAN1 states the following:

''When the B-L072Z-LRWAN1 board is powered by an external power supply through USB FS connector (CN11), in device mode, do not use a PC as power source if the current consumption is greater than 100 mA, otherwise the PC can be damaged.''

As far as i know a PC's USB2.0 port can provide up to 500mA. On the other hand the maximum current consumption of the B-L072Z-LRWAN1 is 300mA.   Why the datasheet recommends not to source power direct from the PC? My test plan is to power and control the CMWX1ZZABZ-091 direct from the USB port. 

Any help would be highly appreciated.Thank you.#cmwx1zzabz-091 #b-l072z-lrwan1 #lora

[T J]

Posted on May 02, 2018 at 02:40

I used the same board with the USB port from the PC, it works well.

[Kostas Papouis]

Posted on May 02, 2018 at 09:56

Hi T J,

Have you connected the USB cable to CN11 connector or CN7? Also have you shorted(or populated 0 Ohm resistors) to the SB15 and SB16? I am asking because SB15 and SB16 are not populated by default and therefore the USB2.0 data signals from the CN11 are not physically connected to the the 

CMWX1ZZABZ-091 LoRa module.