Host Controller Selection
The main program of this project requires a pretty powerful processor. With an ideal image refresh rate between 60-120Hz, here's the calculations for maximum processor throughput and transfer speeds:
Per-Frame Calculations - 6 panels - 64 x 64 LEDs per panel - 8 bits color per LED
6 * 64 * 64 = 24,576 LEDs
8 * 3 colors = 24 bits = 3 bytes
24576 * 3B = 73728 B = 72 KB per full frame
73 KB * 120 FPS = 8,847,360 B / s = 8.8MB /s
This transfer speed is able to happen with a fast parallel bus and DMA or a memory connection.
The processor needs to be able to calculate frames at or above 120Hz, which means calculating 24,576 pixel values 120 times/s. This leads to 2,949,120 operations / sec. Simple operations such as just pixel displaying is easy, negligible performance use. However simulation and calculation, such as a 6-sided digital sand simulation, would require ~3MFLOPS (Mega Floating point Operations Per Second).
STM32 Processor Comparison for LED Cube Project
Compared Families
- STM32N6x7
- STM32N6x5
- STM32H7S3
- STM32H7S7
- STM32H745
- STM32H747
- STM32H562
- STM32H563
High-Level Architectural Comparison
| Feature | N6x7 | N6x5 | H7S3 | H7S7 | H745 | H747 | H562 | H563 |
|---|---|---|---|---|---|---|---|---|
| Core | Cortex-M55 | Cortex-M55 | Cortex-M7 | Cortex-M7 | M7 + M4 | M7 + M4 | Cortex-M33 | Cortex-M33 |
| Max Clock | ~800 MHz | ~800 MHz | ~600 MHz | ~600 MHz | 480 / 240 MHz | 480 / 240 MHz | ~250 MHz | ~250 MHz |
| SIMD / Vector | Helium (MVE) | Helium (MVE) | DSP only | DSP only | DSP only | DSP only | Basic DSP | Basic DSP |
| FPU | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Neural Accelerator | Yes (Neural-ART NPU) | Yes (Neural-ART NPU) | No | No | No | No | No | No |
| GPU | NeoChrom | NeoChrom | Chrom-ART (DMA2D) | NeoChrom | Chrom-ART | Chrom-ART | None | None |
| ISP / Camera | Yes | Yes | Limited | Limited | Limited | Limited | No | No |
| Internal SRAM | ~4.2 MB | ~4.2 MB | ~620 KB | ~620 KB | ~1 MB | ~1 MB | ~640 KB | ~640 KB |
| Internal Flash | External required | External required | Boot flash only | Boot flash only | Up to 2 MB | Up to 2 MB | 2 MB | 2 MB |
| Cache | I + D cache | I + D cache | L1 cache | L1 cache | L1 cache | L1 cache | Cache | Cache |
| External Memory | FMC, XSPI, HexaSPI | FMC, XSPI, HexaSPI | FMC, xSPI | FMC, xSPI | FMC, QSPI | FMC, QSPI | OctoSPI | OctoSPI |
| Security | Advanced + TrustZone | Advanced + TrustZone | Advanced | Advanced | Standard | Standard | TrustZone | TrustZone |
Performance & Capability Analysis (Project-Relevant)
STM32N6x7 / N6x5
Strengths: - Fastest CPU (800 MHz) - Helium vector extensions (major boost for math-heavy simulation) - 4.2 MB contiguous SRAM - Dedicated Neural-ART NPU (~600 GOPS class) - NeoChrom GPU - Modern memory subsystem
Impact on Cube: - Excellent for 3D particle simulation - Large simulation state objects - Multi-buffer rendering - Future ML integration - UI acceleration
Weakness: - Requires external flash - Higher system complexity
STM32H7S7 / H7S3
Strengths: - Very strong Cortex-M7 core - NeoChrom GPU (H7S7) - Mature ecosystem - Good real-time determinism
Limitations: - Much less SRAM (~620 KB) - No AI accelerator - No Helium vector math
Impact: - Capable of 2D/3D simulation - Requires tighter memory management
STM32H745 / H747
Strengths: - Dual-core (M7 + M4) - Good for task partitioning - Up to 2 MB flash
Limitations: - Lower max clock - No AI accelerator - Much smaller RAM than N6
Impact: - Structured multi-core systems - Less ideal for large simulation buffers
STM32H562 / H563
Strengths: - Secure - Efficient - Good general MCU
Limitations: - 250 MHz max - Limited RAM - No graphics accelerator - No ML hardware - No vector extensions
Impact: - Not recommended for high-performance simulation workloads
Vector Math Importance
Cortex-M55 (Helium): - SIMD acceleration - Vectorized float math - Faster matrix transforms - Faster particle integration loops
Cortex-M7: - Scalar floating-point - Strong but not vectorized
For heavy particle systems: M55 + Helium is a major architectural advantage.
Practical Recommendation
| MCU Line | Verdict |
|---|---|
| STM32N6x7 / N6x5 | Best overall choice. Most headroom and future expansion capability. |
| STM32H7S7 | Strong alternative if avoiding N6 complexity. |
| STM32H7S3 | Good but less graphics acceleration. |
| STM32H745 / H747 | Good dual-core option but less memory headroom. |
| STM32H562 / H563 | Not recommended for this application. |
Some of this was formatted or sourced using ChatGPT
N647B0 has been chosen based on given factors
The high frequency and high RAM capacity, coupled with specialized hardware accelerators, it adds a lot of flexibility and expansion for the future of th eproject
However, a major issue arises - lack of onboard flash.