LCD Gauge Update #3: 35 Data Items on 16 Pages!

SLOPOS

This is really nifty. Not sure if you've checked this out yet, but the raspberry pi 7" touch screen fits very nicely in the cubby hole. If I could find a way to cleanly cover up the holes where the hinges go in and out, this would be a great second screen. My head unit also has HDMI input, so might just utilize that but not sure yet if audio will work while viewing HDMI.

*edit* was trying to figure out why that air vent didn't look right - you have a g37 so the above may be useless info

Attached Images

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MotorvateDIY

Not at all! The 370z and G37 CAN bus is very similar and I am working to support both.

How long does you pi take to boot up?

SLOPOS

I'd need to know a bit more about the project to be sure it's even feasible, but a pi3 can fastboot in about 2-3 seconds. I guess I assumed based on the form factor that is what you were using here to run the front end display, but I need to go back and read your other posts.

MotorvateDIY

I am using a $8 ESP-32 micro controller to read the CAN bus, read the Bluetooth data, and drive the LCD display. It is quite the powerhouse!!

Two of the initial design goals was to be affordable and instant start up.

Down the road, I will be looking at using a pi as that will make it easy to drive a larger display. For now, I am focusing on a small (easier to place on the dash) display.

The most difficult and time consuming part of this project has been reverse engineering the CAN bus on multiple Nissan/Infiniti vehicles (like 370, G37, M56, Q50, etc) This is the only way to know if the gauges will work, or what to change in the code so they do work.

SLOPOS

Very familiar with that platform, granted when I was using them they were mostly used for WiFi gpio to control relays and the like, but not much else. Im guessing then you're using i2c for the screen output which wouldn't even require going to a pi as there are plenty of larger i2c screens available and the resolution and refresh rates seem to be adequate. More and more impressed with this project the more I learn about it, thanks for sharing!

MotorvateDIY

I think you meant SPI, not I2C... I2C is too slow for a full colour display.

A 320 x 240 display has 76,800 pixels, and each pixel has 16 bits (RGB565) of colour information, for a total of 1,226,800 pixels or 153,600 bytes per LCD screen/page.

The LCD controller I use supports a max SPI clock of 40 Mhz resulting in taking 0.180 seconds to draw each page. By only "drawing" the parts of the screen that change, the display updates around 30 times per second.

To make the best use of all clock cycles, I use a RTOS (real time operating system) which allows pre-emptive multitasking. This allows me to run multiple tasks at the same time.

The tasks I have set up are: reading the CAN bus, receiving Bluetooth data, and drawing the display. They all run independently and at full speed. Nice!

Also, since the ESP32 has 2 cores, core 0 is dedicated to handling all Bluetooth communications, and core 1 handles reading the CAN bus and rendering the display.

Anyways, I'm glad to share the details...

SLOPOS

Oh, derp! I was thinking esp8266 which didn't have spi capabilities *facepalm* - kinda the little brother of the esp32. I do think I have some 32s laying around from a weather station project I was working on but never finished. Can't wait to see the full published doc - if you need any 370 guinea pigs, feel free to drop be a line.