Hello,
My name is Mariano, from Argentina. I’m an electronic technician, mechanic, and I love to play with electronic projects related to cars.
I’m newbie in this Arduino world, but I had the chance to research, dive and play with code to be creating some basic informational project, such as temperature gaugues (for exhaust, oil and water) with I2C based LCD displays, as well to activate different actuators through Arduino with relays or mosfet.
Since a few weeks I’m dealing with myself and a weird idea, to retrofit an old Renault (Sagem) trip computer with an Arduino Nano on the same enclosure, or an external Arduino Uno, Mega, or even a ESP32. The idea is to keep using the same (old or vintage) LCD display, but replacing the original trip computer board.
If you’re aged, like me, you mostly know of what I’m talking about, but if you’re young, hereby a link in that you can see how this dinosaur works…
https://youtu.be/t-mRz7PlkBI?si=7PZn4Znt8Aq-_ZcJ
Most of these trip computers have been designed and built by a company called Sagem, but of course, there might be different versions, with different features, across the older Renault models (80s models are with green LCD displays, and the 90s models with amber LCD display).
My idea is not to be replicating the exact same “trip” features, but be re-using the same display, specific the numbers (segments section) and some icons, such as fuel, arrows and car icons).
The trip computer mainboard has a NEC D7508G 4-bit microcontroller, and the display has a Hitachi HD44100 40-channel driver
There are only 6 connection pins between the LCD driver and the microcontroller board, so I’m assuming that there are 2 pins for power supply (VCC - GND) and the rest for serial and clock communication (I must read the driver datasheet and then play with my multimeter to check each pin).
I’ve been diving on internet, and also doing some questions to our good friend ChatGPT, and it seems that is always a good idea to have this LCD driver in partnership with LCD controllers such as the Hitachi HD44780 or HD66780, but in this case the driver is driven directly by the microcontroller, so I can assume that it would be possible to drive it also with a modern microcontroller such Arduino.
These boards are old, so the SMD components are still “frendly” to be removed, solder some new cables and re route the display connections to other chips or boards if required.
My idea is to keep learning, doing more research and understand if this is reachable. I do know that there are 100% better choices for Arduino (TFTs, LCDS, also in color) but still, I want to give to this idea a try.
The intention of this post is not to get a “turn key” project from you, all the opposite, so first I would like to ask the next:
- If someone has experience with this LCD driver, if there’s a web page or other post in this community to keep digging into it
- Or if a new driver would be recommended to work in combination with Arduino and this LCD display (if you consider that this is the best choice, I will be really appreciated if you can provide some guidance on which driver should I be looking for)
And is also my idea to share this project with other Renault guys 
I will be posting any new findings on my end.
Thank you in advance for your help!
Kind Regards,
Mariano.
