How Would you solve this Problem, linking MCUs and updating?

How would you coding masters solve this problem?

I am building a old car from scratch and plan to install MCU in the 2 doors, 1 in the front and 1 in the rear.

They will be hard to access once the car is finished so need to be able to update their sketch via some port in the dash of the car, they also must be able to share data.

typically this is done in modern cars using CAN BUS J1939, I have a working prototype of four arduinos sharing date over CAN BUS but can't update them. :confused:

I thought about using ethernet to do this as I have read you can update them by converting the IDE hex. file into bin.file and send it to the correct port address.

the famous I2C witch I am very good with, was in with a chance until I also found out it can't update the sketch :frowning:

any suggestions I would very much like and appreciate.

PS I could add a usb port to all and have 4 USB sockets on the dash board :o but code is king and there must be a newbie way to do it!

Apparently you can update Arduino sketch using Bluetooth but that means you'd need to add Bluetooth module.

ieee488:
Apparently you can update Arduino sketch using Bluetooth but that means you'd need to add Bluetooth module.

I have seen this done but never with 1 bluetooth module to 4 Arduinos. So i have a BLE module connected to the front main AtMega 2560 and I use this to control locks and other items but it is using TX1 and RX1 so not connected to the onboard ch340 chip (clone Arduino)

Why not run a USB or serial Tx/Rx/reset cable along side your CAN cable to the dash?

Think this will have to do