Flight Computer

STM32 MCU Comparison Graphic

Processor Replacements

Replacing Autopilot (F7 vs H7):

• H7: STM32H750, H7B0, H730

• F7 and H7 are both considered “high performance”

• H7 have higher operating frequencies

• F7s have more flash memory than H7s (can offset this with external storage SD, etc.)

• Both offer QFP

Replacing Safety (F0 vs F1 vs ESP32):

• ESP32

  • Versatile,

  • Don’t need ESP32 beefiness + wifi

  • Accurate timers + spi bus are requirements for safety + 16 channels + 15 out (50Hz) + 1 input

  • WONT need wifi on safety

CV Processing (Jetson vs RPi4):

• Firmware has handled this really well

• Nvidia Jetson Research Page

• Current CV Laptop Specs

  • Model: Lenovo Thinkpad T490

  • Processor: i5-8265U base 1.80 GHz boost 3.90 GHz 4 cores 8 threads

  • Memory: 8 GB (2x4) at 2400

  • Storage: SKHynix_HFS256GD9TNI-L2B0B 256 GB SSD

  • Graphics: Intel UHD Graphics 620

H7 Family Breakdown and Analysis

• Dual-core lines: Arm^® Cortex^®-M7 and Cortex^®-M4 cores can respectively run up to 480 MHz and 240 MHz enabling more processing and application partitioning. Dual-core STM32H7 product lines are available with an embedded SMPS for improved dynamic power efficiency. 

• Single-core lines: single-core Cortex^®-M7 offers either great performance at 550 MHz or a unique combination of performance and power saving at 280 MHz and 34 µA (typ) in STOP mode.

• Value lines: With an embedded 128 Kbytes Flash memory, the STM32H750/B0 MCUs are cost-effective STM32H7 devices.

• Big Questions:

  • Do we want a dual-core processor? Is Zeropilot software ready to run on dual-core (likely require some refactoring)?

  • What is our operating frequency requirements? (max. of 550MHz for single core OR 480MHz +240MHz for dual core)

  • What is our RAM requirements? (max. of 1 MB to 1.4MB)

  • What is our memory requirements? (max. of 2MB)

  • Are the connectivity options enough for us?

  • Was the old processor able to handle everything we wanted it to handle? Did it struggle with anything specific? (old was gucci)

  • Cost <$30

• Do we need to worry about these features/do we care?:

  • JPEG Codec

  • TFT-LCD & MIPI-DSI & Chrom-GRC (graphic oriented memory management unit)

  • Industrial Grade Temperatures? (I don’t think we need -40degC to 125degC ambient temps)

  • Ethernet

  • Octo-SPI (look into this a bit more)

In-Depth Analysis of Processor Selections