First of all this is no library. It is the very first version of very basic C programming for sending & receiving Data to Bluepill from PZEM-004T by UART under Modbus Rtu Protocol. You may copy the code to work with STM32 Bluepill & PZEM-004T V3 module. The code is under development. Please change the slave address according to your module.
Disclaimer: Use the code on your own risk. Again mentioning that, the codes are still under development. So be cautious while using it.