I am not in embedded development, but I was in software development and I also did recruitment and selection, That was well over a decade ago and it was in the USA. I am not familiar with the Mexico market (as shown in your locale flag). I suspect USA and Mexico hiring method would be some what similar and this may be helpful.
For entry level or near entry level, what I would look for is someone with recent and related software develop experience. Reason of potential job switching, and why this candidate will be suitable and would likely succeed if hired. The most important factor I will leave to a later paragraph after the skill related ones.
I think it would be helpful if you can show what makes you a good software developer. Modifying scripts and python file alone does not make you a compelling candidate. Since your graduation is three years ago and in EE (may not be as programming focused as the employer likes when compared to Computer Science), that's the cards you got and you have to make the best of it. Mean time, you can shore up.
Making the best of it means shinning the best light in what you have done and how it relates to what you will do if hired. Emphasizing things that will benefit your new employer without exaggerating. Rather than exaggeration, display pride. "I was proud of being able to complete that because of this issue and that issue and those road blocks that you had to overcome. So, the emphases is your resourcefulness, creativity, tenacity to overcome road blocks and got it done -- as oppose to emphasizing and/or exaggerating the technical complexity of the tasks. Exaggerating technical achievement to the point of almost lying or outright lying usually is easily discerned. Since you don't have much there, talk more about why you are special - you can get it done while others more technically competent may instead got stuck in the tar-pit because they lack those qualities you got. You know yourself best. If resourcefulness, creativity, tenacity doesn't describe you, find some other attributes you have that an employer would value. If they are not good enough yet, develop them to the point they are. Even if you consider them good enough, it should not stop you from developing them further.
For embedded programming, your EE background will put you ahead of those from application development background where they are a few layers sheltered from the hardware. That said, stuff like "in car entertainment systems" also has software that is more a UI development than hardware control. How you can best position will depend on what job you are shooting for. Start looking at job ads, see what skill they are looking for that you can develop on your own.
Chances are, you are not going to an interview tomorrow. So you have time between now and your interview to learn more. Use that time. As of now (from what you wrote here), one can say your software development experience is rather low. So it would be a good idea for you to develop some skills starting right this moment so by interview time you can (a) demonstrate such skills, and (b) is able to talk intelligently about that area in an interview. The more software development skills you can stuff into your brain and portfolio (to show), the better off you will be.
Now the most important factor I said earlier that "I will leave to a later paragraph." This is something I learned from books I found very useful. In a nutshell: for project related hires, I hire for skill. For career hires, I hire for attitude. Skill is easy to learn, but a person's attitude is much harder to change. May be your next boss doesn't think the same way. For me, a good attitude always beat out current depth of knowledge. Throw him a book and he'll learn, but if no body like him and no body trust him, there is not much I can do about that. So, make sure you have a good attitude and a positive-one. [In this context, take attitude to mean: commitment to good work, trust worthy (remember: schedule forecast and budget are also promises), service-attitude (is the customer, ie: me as your boss, satisfied?), ethics, etc., etc. As to "positive attitude", that means a can-do attitude: look for how you can get it done rather than why it can't be done. Talk about the difficulties by all means, but do so with the pasture of "it isn't going to stop me from getting it done." Always.]
This is but my own personal experience and what I personally practiced. It may not be applicable widely. None the less, I hope it is helpful to you in some way. Best of luck to you.