Hey y'all (yes, I'm in Texas),
I have really appreciated all of the good ideas and thoughtful design ideas here. There are some apples and oranges being discussed at times because the problem of BBB reliability is not single-fold. In the hopes of providing a clearer "Big picture" of the issue, as well as to summarize some of my own research on the topic, I've attempted to capture the main points in this thread into an outline format. If it is convenient, you can refer to specific problems/solutions/caveats by the outline number, ie ( III.A.1 ) in any subsequent discussions -- this kind of shorthand might clarify the issues that are being discussed, rather than having to spell this stuff out (or omit it) when talking about a point. Is there a good spot on a WIKI for this somewhere? Enjoy, and thank you! ST -------------------- DOCUMENT IS BELOW HERE *SUMMARY BBB RELIABILITY PROBLEMS & FIXES:* *I. Problems:* *A. System/Client Software Problems:* * 1. Problem: Incomplete system/client sw startups ( why? -- can damage result with this? )* * 2. Problem: Incomplete system/client sw shutdown* * a. Can cause system corruption* * 3. Client or system software freeze-up (it can happen!)* * a. Can freeze device operation even in absence of power issues* *B. Hardware Problems:* * 1. Problem: BBB doesn't always restart without a hard-disconnect of power (known hardware issue)* * a. Always - when shutdown/halted (ie shutdown/halt)* * b. Sometimes - when hard cycled (ie power removed, reset button pushed)* *C. Power problems* * 2. Problem: Mains power can't be relied upon* * a. Power loss (ie blackouts)* * b. Partial power loss (ie brownouts)* *II. Requirements:* * A. A "Reliability System" to address above problems. * *III. Needs:* * A. Backup power source for* * 1. BBB until complete shutdown* * 2. Additional components of reliability system* * B. Hard-Reset Circuit: to completely remove, and re-add power to the board (for I.B.1 above)* * C. Sensing: Need to detect* * 1. Power off: both presence and duration (ie detect/differentiate I.C.2.a and I.C.2.b)* * 2. System soft-freeze up (detect I.A.3)* * 3. Power on: both present, and "Good" (ie good enough for full reboot + protected powerdown)* * D. State Machine to enforce guaranteed order, no matter what* * 1. "Protected Shutdown": Complete shutdown after it has been initiated* * a. even if power up is specified during shutdown (in which case protected startup begins thereafter)* * 2. "Protected startup": Complete startup once it has been initiated* * a. even if power is removed during startup (in which case protected shutdown follows)* * 3. "Power Good" before Startup: Power remains detached until enough backup power for Protected Startup + Protected Shutdown* * 4. "Complete" Power off after shutdown: Complete detachment of power from BBB to solve (I.B.1)* * 5. Others?* *IV. Solution Design Components/Approaches* * A. Backup power* * 1. Li-po Battery backup * * a. Pros:* * i. Long lasting* * ii. Relatively simple circuitry to support* * iii. Greatest capacity* * b. Cons:* * i. "Dangerous", thus travel/shipping restrictions* * ii. Limited recharge cycles* * 2. Super capacitor-based Backup Power* * a. Pros:* * i. No practical recharge cycle-limit* * ii. "Safe" enough for restrition-free transport/shipping* * b. Cons:* * i. Increased circuit complexity, esp for 2-cell systems needed to produce 5v* * 3. Coin-cell (to power Reliability System only)* * a. Pros:* * i. Cheap* * ii. Long-lasting (10+ years)* * iii. "Safe"* * b. Cons:* * i. Only powers reliability system, need additional solution for BBB* * B. Hard Reset Circuit (Pretty well known problem with solutions out there)* * 1. Relay (physical, or solid state)* * 2. Some kind of transistor switch* * C. Sensing* * 1. Mains Power off* * a. Voltage comparator of some sort* * 2. System "Soft-freeze"* * a. BBB On-board software-controlled watchdog timer initiates reboot* * 3. System initiated shutdown* * a. GPIO pin connected to Reliability System, change state on start* * 4. System completed shutdown * * a. heuristic delay after final GPIO pin state change on end (from IV.C.3.a just above)* * 5. System initiated startup* * a. Implied action on "Power Good" (add'l sensing not needed)* * 6. System completed startup* * a. GPIO pin connected to Reliability System changes state on "Startup complete"* * 7. Mains Power On* * a. Voltage comparator of some sort * * 8. Mains Power "Good" (enough backup power available for Protected Startup + Protected Shutdown* * D. State Machine* * 1. An MCU of some sort* * a. MSP430 series (William Herman/Wulfmans's recs)* * i. Pros: * * * very low power + coin cell battery == >10 years backup life* * * onboard ADC for voltage measurement/sensing* * * inexpensive* * b. ST Micro series (ie STM8)* * c. NXP's LPC800 series* * 2. Discrete logic state machine* * a. Pros* * i. More tolerant of brownouts(?) than unprotected MCU* * b. Cons* * i. Lots of soldering! * * 3. Hybrid Technology - Programmable Mixed Mode Circuits* * a. Silego GreenPak (John3909's rec)* * i. Pros* * * Nice dev kit ( < $60 )* * * Very inexpensive ( < $0.40 )* * * More tolerant of brownouts(?) than unprotected MCU (John can you comment on this?)* *V. Commercially Available Solutions* * A. Andice Labs Power Cape (Available for BBB/RaspberryPi)* * http://andicelabs.com/beaglebone-powercape/* * Li-Po Battery Backup, with software readable battery voltage and current* * ~ $65 (with headers) * * B. Juice4Halt (Built for RaspberryPi, not BBB, but could be repurposed, one would assume)* * http://juice4halt.com* * Dual Super-capacitor Backup, with State Machine implemented* * ~ $85 (5V, all told shipped to US)* * C. Others?* -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. 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