I have built a PCB that does everything I want it to, but now I need to cut costs. If you guys could give me a hand with that I'd appriciate it a lot as I don't have much time left for trial and error. So here is what I need the PCB I design to do:
1-It needs to read 3 temperature sensors (NTC like).*
2-It needs to have a SIM800, an ESP8266 and an ethernet connection (This is actually 3 different boards, one has only SIM800, one has a SIM800 and an ESP8266, one has SIM800 and ethernet connection).
3-It needs to drive a 4x20 display preferably over I2C, or if it's possible a GLCD.
Now like I said, I've built this PCB, it's on my desk right now with everything I want. But the thing is, this thing costs too much as I am using an Arduino Mega 2560 instead of just a ATmega2560, a SIM800L module instead of a SM SIM800 etc etc. So instead of just putting this out like that, I'm thinking about using an ATmega2560 or an ATmega328P. If it's possible I'd rather using direct SMD chips for everything I mentioned above actually. What I'm asking you is, as I've never actually done it before:
1-Let's say if I were to use an ATmega328P, mounted on a PCB, what is the easiest way to burn a bootloader to that (a schematic would help really, I'm a programmer and not an electrician and when someone says put a diode between something and something I really can't wrap my head around it without trial and error)?
2-If I succesfully burn a bootloader, can I use my Arduino libraries that I use on normal Arduino boards?
3-I believe if I was able to burn a bootloader, I can program it the same way, am I correct?
4-Right now I have ESP8266 attached on Hardware Serial, should I change that to Software Serial? Is using Software Serial even possible in that case?
5-For devices like SIM800, ESP8266, LM2596 and ENC28J60 I'm just thinking about copying their board from a datasheet to mine, would that work?
I'd really appriciate any advice, about any connection that I need to do on the devices I mentioned above. If you have something you have about the ESP side, please enlighten me, I have never ever worked on a project like this before and I really really don't have much time to do trial and error.
*Some temperature sensors need to read temperatures below -55 which is under the limit NTC can read. I'm thinking about using PT-1000s or PT-100s but if you have a suggestion about that too, I'd really really appriciate it. Also I will probably need to read humidity in some cases but I know PT sensors can't read humidity, I was thinking about just a basic humidity sensor to accomplish that.
That was a long one, thanks for reading it! Have a nice day!