I found the following books quite useful in my study of "Embedded Systems/Hardware" coming from a purely Software background. Without overwhelming you they provide just the right level/amount of Hardware knowledge to get you going.

1) Designing Embedded Hardware by John Catsoulis.

2) Introduction to Embedded Systems: Using Microcontrollers and the MSP430 by Manuel Jimenez et al.

3) Prototype to Product: A Practical Guide for Getting to Market by Alan Cohen.

You can also look at using Digilent equipment (eg. Analog Discovery 3 or 2) and learning materials along with Arduino/MSP430/whatever to get better practical insight into your system - https://digilent.com/reference/landing and https://digilent.com/reference/learn/start