Friday, 4 April 2014

usb - How to force variable voltage fast charging power bank to output a certain voltage?


I am trying to power up my raspberry pi 3 with a Xiaomi 10000mAh fast charging power bank through the L298N motor controller. The motor controller can receive from 7 to 35V, and it has a 5v output, which I use to power my pi through the 5V pin. I also use a USB 2.0 to TTL UART Module 6Pin Serial Converter (https://www.aliexpress.com/item/CP2102-USB-2-0-to-TTL-UART-Module-6Pin-Serial-Converter-STC-Replace-FT232-Module/32534146426.html).


I read a bit about fast charging and how they control the voltage, and this is how the charger decides what voltage to output using the d+ and d- pin: https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgE42tqDd1HS3GLwHVDGwg4Te0K__1FNjGYzar890eDccm3Ql_qQwZ6f7-VM1nEsTYYylWibHvL1eSWiqUSxpylkJThXAr-60jA3_Xt_quRHC070qFPexa2pHhg-aeOGSXQOeg0Qgc-FQoD/s1600/USBVoltage.jpg


The first problem is that the usb converter doesn't have the D+ and D-, but I believe it should be the RXD and TXD pin. I want my power bank to output 9V to the motor controller so I tried plugging a 3.3V to the 0.6V to the RXD and TXD (tried both way) but it doesn't change the output voltage. The second problem is that if I just plug the power bank to the motor controller, which it will automatically output 5V, it doesn't turn on the Pi.


I am new to these kinds of stuff so any suggestion on how to do this will be really helpful. Thank you.




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