Olis Blog

Color TFT/OLED Trip Computer

Ich habe 2015 mit der Entwicklung eines Fahrtcomputers für Firebirds/Camaros begonnen, und irgendwann kam mir die Einsicht, dass so ein Teil auch im Fiero nicht schlecht sein würde. Daher stelle ich die Informationen über dieses Projekt auch hier zur Verfügung, allerdings handelt es sich dabei um ein Projekt, das sich noch in Entwicklung befindet, und ausserdem ist der Text vorerst noch Englisch. Wenn die Entwicklung abgeschlossen ist, werde ich das Ganze vielleicht auch eindeutschen, aber interessiert den Einen oder Anderen ja auch die Vorabinfo und Entstehungsgeschichte...

The DashComputer project

This project started out as an idea for replacement of the Camaro's LCD odometer with a color OLED display with graphics capabilities. Based on a monochrome OLED display concept I had designed for the 98-02 F-body instrument cluster and different embedded trip computers I have designed and built for the Fiero instrument cluster work began on a versatile computer control module for dash instrument clusters of various vehicles. The project was named "DashComputer".

While initially targeted for the Camaro only it quickly became apparent that this gadget would be useful for more vehicles, since the display with its compact dimensions of 1.6" diagonally would fit into a variety of vehicles. The display is about 1/2" thick and the advantages of OLED are high-contrast, crystal clear colors combined with a wide temperature range and wide viewing angle. The only downside is the limited lifetime due to burn-in over its lifetime of 12.000 hrs (although a slight burn-in can be noticeable considerably sooner, especially if the display is run at high contrast settings). But, if the burn-in really gets distracting: the display isn't too expensive and can easily be replaced. Yet, the OLED does decay so alternatively a TFT of virtually identical dimensions can be used as well, although the contrast isn't as crisp as the OLED's.

Due to the limited space in an instrument cluster the display unit is a sandwich of two circuit boards, yielding compact dimensions and mechanical stability for the fragile display glass with silicon chip-on-flex circuit board. The display unit is connected to the control module via 8 wires. The control module is about 4x3" and should be located close to the instrument cluster to keep the wires to the display module short. Since the Fiero instrument cluster is modular, it was feasible to design a replacement circuit board for the speedometer module that integrates all trip computer and speedometer components on a single board, thus eliminating the separate electronic control module and connector that the F-body and other cars need.

This electronic control module is the heart of the system, serving as a platform for a variety of applications. The module is customized to its vehicle through a custom firmware that is user updateable via USB. The universal module is connected to the vehicle using a standard Delphi 32-pin Micropack connector also used by GM in vehicle electronics, assuring availability of connector components for years to come. The Fiero module is connected through the stock speedometer connector. Since updates can be performed on-board through USB, the universal module can be mounted hidden anywhere under the dash without the need to physically access the module for software updates.

Key features

The hardware supports the following features:

• Connects to a serial TFT or OLED module
• Customizeable to vehicle
• Customizeable with color startup ("splash") screen with 256 out of 262K colors
• Customizeable with color background screen with 256 out of 262K colors
• Many customizeable items
• Firmware USB updateable by user, no special hardware required
• Firmware can be updated using Android phone/tablet
• Odometer settable by user application
• 2000 ppm / 4000 ppm vehicle speed inputs found in many GM cars
• Up to two temperature sensor inputs using standard GM temperature sensors
• Can be configured to display system voltage
• Multiple pushbutton inputs
• Battery backed clock / trip computer values using either button cell or vehicle battery (Fiero: vehicle battery only)
• Input for digital Dinsmore compass sensor module (not available on Fiero unit)
• ALDL ECM communication suitable for C3 and P4 computer systems (160 / 8192 baud)
• IP illumination voltage input and PWM illumination LED driver output for custom LED IP illumination
• Piezo speaker for user alerts (8 Ohm speaker for Fiero version)
• RS232 compatible input for NMEA GPS mouse
• CAN bus for interfacing with select radio head units and future extensions.

Technial data:

• Supports SPI OLED and TFT modules (SSD1353 OLED or ST7735 TFT controller), 262.000 colors (18 bit)
• 25 MHz Freescale automotive grade microcontroller with 240K memory
• FTDI USB controller supported by Windows/MacOS/Linux for firmware updates
• Current requirement with ignition off < 1mA
• LED driver delivering up to 700 mA for custom cluster illumination, e.g. 140 LEDs of 20mA in strings of four (not available on Fiero model)
• Standard CAN bus driver with 120 Ohms termination on board
• Optional backup battery: CR2032 button cell, ~10 years endurance (not on Fiero)
• OLED operating lifetime: 16000hrs @60Cd/m2

Not all functions are available in all firmwares, but the hardware platform is compatible across all vehicles!