Display Hardware Rationale
- Akshay Gaitonde
Status | In progress |
Owner | @Akshay Gaitonde |
|---|---|
Contributors | @Akshay Gaitonde |
Approver | @Diya Rajon |
Due date | ? |
On this page |
🌍 Overview
This is the hardware design of the display, including the panel as well as any graphics driving hardware associated with it.
Problem statement
Controls must show the driver critical information relating to the state of the car (i.e. speed, backup video feed, BPS faults, etc.). Controls is also tasked with ensuring the driver has enough information for simple actions such as turning.
Research insights
There are many different configurations for the display. We can drive the display using an external computing device such as a Raspberry Pi. We also have a choice of display panels, display size, and display interface.
Solution hypothesis
The solution is successful if we are able to view pertinent data in readable formats (i.e. speed is displayed as decimal numbers, icons if used can be rendered, etc.).
Design options - Graphics Driving Hardware
There are multiple ways we can display graphics. We want to have some nice graphics and a better time programming them than the previous design that utilized Nextion software. With that, we have 3 options.
| Option 1 - Raspberry Pi Zero | Option 2 - Raspberry Pi 4/5 | Option 3 - Custom board + display library |
|---|---|---|---|
Overview | Use an off the shelf device for running a graphical application and keep it small. | Use an off the shelf device for running a graphical application but including some ports like Ethernet and full size USB. | Use the integrated graphics processing library and a controls board we design to drive graphics. [OLD DESIGN] (i.e. Daybreak’s Nextion display) |
Pros and cons | Low power
Cheaper
Python/C development |
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Decision 1
- Option 1 - Raspberry Pi Zero
We prioritize compact circuitry as well as being able to develop in a more developer friendly environment.
Design options - Display Panel Type
There are also multiple panel options we can consider. We want the ability to display graphics in color through a medium that is robust in light/dark environments, refreshes decently fast, consumes as little power as possible, and is cost effective.
| Option 1 - IPS/LCD Panel | Option 2 - OLED Panel | Option 3 - TN Panel |
|---|---|---|---|
Overview | LCD panels are commonly used in industrial and consumer electronics applications because they have pretty solid color accuracy, viewing angle allowance, and brightness. | OLED panels are more common in artistic environments and gaming because they have the best color accuracy and vividness as well as good viewing angle ranges. | TN panels are falling out of favor because even though they typically update the fastest, they have much worse colors, brightness, and viewing angle range. |
Pros and cons |
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Decision 2
- Option 1 - IPS/LCD Display
We want a display that can be viewed from multiple angles while prioritizing the power efficiency. IPS/LCD offer a compromise between the two.
Design options - Display Communication Interface
There are multiple ways we can communicate with the display from the graphics driving hardware. We want an interface that is reasonably implementable (meaning we could make it or buy it easily), is suitable for video streaming, and is manageable to wire.
| Option 1 - HDMI | Option 2 - UART | Option 3 - SPI |
|---|---|---|---|
Overview | HDMI is used for monitors, TVs, and other video media. It is a proprietary protocol that transmits video and audio (depending on the HDMI version). This protocol specifically is optimized for streaming audio/video feeds. | UART is a simple protocol for asynchronous serial communication. It's widely implemented (it only uses a few IO pins). It also is what we already use with our current leader board and display. [OLD DESIGN] | SPI is a common communication protocol used in embedded systems. The protocol allows for one controlling device (the master) to send data over short distances to several receiving devices (the slaves). |
Pros and cons |
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Decision 3
- Option 1 - HDMI
We want something simple and robust. In the past, we have had issues with SPI, so we used UART in Daybreak (2023-24 car). However, wiring one HDMI would be even better, especially if we use a device like a raspberry pi to drive our display interface graphics.
Design options - Panel Configuration
We can have many different sizes and configurations for our display. This decision is motivated by what things we want to specifically include on the display(s). We have 3 options motivated by how we want to compartmentalize certain graphics, namely video feeds.
| Option 1 - Long boi display | Option 2 - iPad size display | Option 3 - Multiple sizes | Option 4 - Small boi display |
|---|---|---|---|---|
Overview | This allows us to display everything on one horizontal line. It essentially extends the current display size only horizontally. (i.e. 1300x400) | This allows us even more screen real estate to display everything. It’s what you would expect an infotainment screen to be at minimum size (7”-12” diagonal). | This allows us to compartmentalize video feeds into different screens. We could use our current display architecture for displaying important data like speed, battery voltage, etc. and have other displays for each video feed. | Use the same or similar small boi display that we already have. This is optimal to only include important information and have different screens in software for additional views. [OLD DESIGN] |
Theoretical Display Layout |  |  | ||
Pros and cons |
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Potential Candidates |
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Decision 4 [NOT DECIDED YET!!]
We still have not decided on the final display yet. Options are linked above. We are currently deciding between the pad displays and the long boi.
Akshay Preference:
Lilliput 719/C 7" HD Commercial Monitor
Justification:
1000 nits is pretty nice
it accepts 9-36V power (so 12V works well for it)
consumes <8.5W (according to product page but I suspect that if we have the brightness at a reasonable level like 500-600 nits we can achieve this)
standard resolution and aspect ratio (shouldn’t be weird with R Pi )
$189 might be too much??
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