Hello everyone,
I'm picking this project back up and could use your expertise regarding an ongoing issue: communication between the main and secondary PCBs. While most other issues have been addressed, I'm still struggling with this specific aspect. Here's a structured overview to clarify the current situation:
Project Goals:
- Prioritize reliability, user experience, and ease of installation/maintenance.
- PCB cost isn't critical; investing in durability and long-term reliability is justified due to installation expenses.
Main PCB Specs:
- Processor: Raspberry Pi CM4/CM5 (for premium, high-res touchscreen experience).
- Display: Currently 2560x1600 @50-60Hz, future-proofing to 4K @30fps.
- Location: Installed on the secure side (ceiling-mounted).
- Additional MCU: RP2350b for managing critical functions (e.g., fire alarms, emergency stops, door relays).
Secondary PCB Specs:
- Processor: RP2350b managing NFC reader, GPIO (tamper detection, LED indicators).
- Display Integration: Contains ICs/connectors for the high-res display.
- Location: Directly behind the display, emphasizing minimal size and efficient thermal management.
Key Communication Requirements:
- Standardized installation using common cabling types.
- Typical inter-board distance is ~2m, but longer distance capability preferred.
- Remote firmware flashing capability from the main to the secondary PCB.
- Must support video, data communication, and power.
Current Firmware Flashing Concept:
I'm considering a "one-shot" hardware timer solution triggering a reset and BOOTSEL if a MOSFET isn’t toggled within ~60 seconds. I'm open to better alternatives, especially since I haven't fully reviewed the RP2350 datasheet yet.
Communication Methods Evaluated:
1. USB-C:
+ HDMI-alt mode, USB data, power delivery.
- Limited cable length (2-3m), costly extenders.
2. HDBaseT:
+ Comprehensive solution.
- Difficult sourcing, high cost.
3. HDMI over IP:
+ Enables signal and PoE via main PCB.
- Concerns about latency and image quality; currently testing with ordered kits.
4. HDMI over Cat6:
+ Dedicated HDMI signal plus power/data on separate cables.
- Potential complexity, risk of mixing up cables/connectors, may require additional extenders.
5. HDMI Micro and Ethernet
+ HDMI micro cable, separate Ethernet POE cable. Way cheaper PCB.
- HDMI max run length limits. Problems with fitting HDMI Micro in installation. Sensitive to vibrations
Additional Thoughts:
- Long-distance cabling could potentially allow one main board to manage two secondaries, saving installation costs in setups with multiple doors.
- Considering a secondary PCB mode without the high-res display, using a simpler screen/keypad setup with RS485 or IP-based communication.
Do you see any alternative solutions or approaches I might be overlooking? Multi-cable setups are acceptable, though simplifying the installation is ideal.
Thanks for any insights or recommendations you can provide!
I'm picking this project back up and could use your expertise regarding an ongoing issue: communication between the main and secondary PCBs. While most other issues have been addressed, I'm still struggling with this specific aspect. Here's a structured overview to clarify the current situation:
Project Goals:
- Prioritize reliability, user experience, and ease of installation/maintenance.
- PCB cost isn't critical; investing in durability and long-term reliability is justified due to installation expenses.
Main PCB Specs:
- Processor: Raspberry Pi CM4/CM5 (for premium, high-res touchscreen experience).
- Display: Currently 2560x1600 @50-60Hz, future-proofing to 4K @30fps.
- Location: Installed on the secure side (ceiling-mounted).
- Additional MCU: RP2350b for managing critical functions (e.g., fire alarms, emergency stops, door relays).
Secondary PCB Specs:
- Processor: RP2350b managing NFC reader, GPIO (tamper detection, LED indicators).
- Display Integration: Contains ICs/connectors for the high-res display.
- Location: Directly behind the display, emphasizing minimal size and efficient thermal management.
Key Communication Requirements:
- Standardized installation using common cabling types.
- Typical inter-board distance is ~2m, but longer distance capability preferred.
- Remote firmware flashing capability from the main to the secondary PCB.
- Must support video, data communication, and power.
Current Firmware Flashing Concept:
I'm considering a "one-shot" hardware timer solution triggering a reset and BOOTSEL if a MOSFET isn’t toggled within ~60 seconds. I'm open to better alternatives, especially since I haven't fully reviewed the RP2350 datasheet yet.
Communication Methods Evaluated:
1. USB-C:
+ HDMI-alt mode, USB data, power delivery.
- Limited cable length (2-3m), costly extenders.
2. HDBaseT:
+ Comprehensive solution.
- Difficult sourcing, high cost.
3. HDMI over IP:
+ Enables signal and PoE via main PCB.
- Concerns about latency and image quality; currently testing with ordered kits.
4. HDMI over Cat6:
+ Dedicated HDMI signal plus power/data on separate cables.
- Potential complexity, risk of mixing up cables/connectors, may require additional extenders.
5. HDMI Micro and Ethernet
+ HDMI micro cable, separate Ethernet POE cable. Way cheaper PCB.
- HDMI max run length limits. Problems with fitting HDMI Micro in installation. Sensitive to vibrations
Additional Thoughts:
- Long-distance cabling could potentially allow one main board to manage two secondaries, saving installation costs in setups with multiple doors.
- Considering a secondary PCB mode without the high-res display, using a simpler screen/keypad setup with RS485 or IP-based communication.
Do you see any alternative solutions or approaches I might be overlooking? Multi-cable setups are acceptable, though simplifying the installation is ideal.
Thanks for any insights or recommendations you can provide!
Statistics: Posted by Jesper_ITOS — Tue Apr 29, 2025 2:28 pm