Bare Metal Programming Guide von Sergey Lyubka
https://github.com/cpq/bare-metal-programming-guide

   I am Sergey Lyubka, an engineer and entrepreneur. I hold a MSc in Physics from
   Kyiv State University, Ukraine. I am a director and co-founder at Cesanta - a
   technology company based in Dublin, Ireland. Cesanta develops embedded
   solutions:

   https://mongoose.ws - an open source HTTP/MQTT/Websocket network library
   https://vcon.io - a remote firmware update / serial monitor framework