What the interviewer wants
- Framebuffer and memory plan
- Rendering and flush strategy with LVGL
- How you keep the UI from starving the rest of the system
Constraints
- 1 MB internal SRAM and 16 MB external SDRAM on a 16-bit FMC bus
- Colour depth: RGB565 or ARGB8888, your choice
- Pixel clock about 30 MHz; refresh 60 Hz
- Touch controller on I2C with an interrupt line
- D-cache enabled
If you ask the interviewer
- Is there a GPU beyond DMA2D? No. DMA2D only.
- How much of the screen changes per frame? Usually small regions; a few screens have full-screen transitions.
- Fonts and images? About 3 MB of images and fonts in external QSPI flash, memory-mapped.
How it's graded
The rubric a senior interviewer would use. Each item is scored 0 to 3 and weighted.
| Memory and bandwidth budget | weight 3 |
| Tearing and buffer swaps | weight 3 |
| Acceleration and caching | weight 2 |
| System integration | weight 2 |
| Measuring performance | weight 1 |
| Validation | weight 1 |
How to structure your answer
- Requirements and assumptions: the numbers that drive the design.
- Architecture: blocks, tasks, data flow, memory.
- Key decisions and trade-offs, with the alternatives you rejected.
- Failure modes and recovery.
- Testing and validation.
More design rounds
Write your design in five sections and get it graded against this rubric, with a follow-up question from the AI interviewer.
Answer this round