There are several free online courses available for learning embedded electronics and programming in C/C++. Here are a few options you can explore:

1. edX – Embedded Systems – Shape the World: This course is offered by the University of Texas at Austin and covers the fundamentals of embedded systems, including C programming for microcontrollers. It focuses on hands-on learning using the MSP432 LaunchPad development kit. You can audit the course for free, or you can choose to pay for a certificate.

1. Coursera – Introduction to Embedded Systems Software and Development Environments: Offered by the University of Colorado Boulder, this course provides an introduction to embedded systems programming using the C programming language. It covers topics such as data representation, memory management, and peripheral interfacing. While the course is free to audit, you have the option to pay for a certificate.

1. MIT OpenCourseWare – Introduction to C and C++: This course from MIT provides an introduction to the C and C++ programming languages. While it is not specifically focused on embedded systems, it covers the basics of these languages, which are widely used in embedded programming. The course materials, including lecture notes and assignments, are available for free on the MIT OpenCourseWare website.

1. Embedded Systems – Shape The World: Multi-Threaded Interfacing: This is the second part of the “Embedded Systems – Shape the World” series offered by the University of Texas at Austin. It covers advanced topics in embedded systems, including multi-threaded programming and real-time operating systems. The course materials, including lecture videos and lab exercises, are available for free on YouTube.

1. Nandland – Embedded Systems Basics: This online resource provides a collection of tutorials on embedded systems basics, including microcontroller programming in C/C++. It covers topics such as digital logic, memory, and peripherals. The tutorials are available for free on the Nandland website.

Remember to check the availability and course details on the respective platforms, as they may have different enrollment periods or certificate options. Additionally, keep in mind that while these courses are free, some platforms may offer paid certificates or additional features.