4 ms·

Which mcu are you using ? The possibility of noise becoming a flash command is practically 0. Also too much noise will more importantly corrupt you ram. Flash c

Which mcu are you using ? The possibility of noise becoming a flash command is practically 0. Also too much noise will more importantly corrupt you ram. Flash can be sensitive to noise and that can cause bit flips.

calamari4065 3y ago
>The problem also happened exceedingly rarely -- we needed about 100 of these devices to run constantly a certain operation and it took us to wait for about a week until one of these devices died That's one failure per 16,800 hours, or 700 days. That's pretty goddamn rare.
- MassPikeMike 3y ago
  Once you have 700 units in the field, one failure per 700 days is no longer quite so rare.
- eep_social 3y ago
  And that’s running the particular op repeatedly, so in practice it’s an even rarer event. However with “millions of them in the wild” it doesn’t matter. Scaling is tough.
- onetimeuse92304 3y ago
  We had to clean out a small warehouse and repurpose it for testing rig. We have created a piece of hardware to do automated testing and recording, and then we created a small production chain to and produced 100 of them. Fortunately, we already had all the design, development and production resources to do the project on site (yes, we were doing it all, not outsourcing to China).
- deleted 3y ago
  [deleted]
rcxdude 3y ago
from the description the flash was on a separate chip: I would guess most likely a SPI interface. You can absolutely get noise picked up on a SPI interface which looks like a command: and if an erase command is 16 bits long, you are going to see that command just with random bits every so often.
- onetimeuse92304 3y ago
  Yes, it was separate chip (per description). Yes, it was SPI flash. And yes, the word was 16 bits.
onetimeuse92304 3y ago
1. What does choice of MCU have to do with it? 2. Noise can definitely affect other components. Traces are antennas that both broadcast as well as receive signals. As technology marches forward, the voltages and tolerances for communication become smaller and tighter. At the same time, you integrate more functionality on the board so maybe your sensitive MCU and flash and ram are all living close by to some radio equipment and PSU and whatever else. Power interruptions to certain components can create momentary flashes of noise that can act as EMP bomb going off. On other occasions a noisy, badly designed high frequency power component can emit noise that is picked up by some random traces due to their geometric configuration and length. Your comment suggests you never worked on a large project with thousands of components and dozens of major chips?

calamari4065 3y ago

>The problem also happened exceedingly rarely -- we needed about 100 of these devices to run constantly a certain operation and it took us to wait for about a week until one of these devices died That's one failure per 16,800 hours, or 700 days. That's pretty goddamn rare.

MassPikeMike 3y ago
Once you have 700 units in the field, one failure per 700 days is no longer quite so rare.
eep_social 3y ago
And that’s running the particular op repeatedly, so in practice it’s an even rarer event. However with “millions of them in the wild” it doesn’t matter. Scaling is tough.
onetimeuse92304 3y ago
We had to clean out a small warehouse and repurpose it for testing rig. We have created a piece of hardware to do automated testing and recording, and then we created a small production chain to and produced 100 of them. Fortunately, we already had all the design, development and production resources to do the project on site (yes, we were doing it all, not outsourcing to China).
deleted 3y ago
[deleted]

rcxdude 3y ago

from the description the flash was on a separate chip: I would guess most likely a SPI interface. You can absolutely get noise picked up on a SPI interface which looks like a command: and if an erase command is 16 bits long, you are going to see that command just with random bits every so often.

onetimeuse92304 3y ago
Yes, it was separate chip (per description). Yes, it was SPI flash. And yes, the word was 16 bits.

onetimeuse92304 3y ago

1. What does choice of MCU have to do with it? 2. Noise can definitely affect other components. Traces are antennas that both broadcast as well as receive signals. As technology marches forward, the voltages and tolerances for communication become smaller and tighter. At the same time, you integrate more functionality on the board so maybe your sensitive MCU and flash and ram are all living close by to some radio equipment and PSU and whatever else. Power interruptions to certain components can create momentary flashes of noise that can act as EMP bomb going off. On other occasions a noisy, badly designed high frequency power component can emit noise that is picked up by some random traces due to their geometric configuration and length. Your comment suggests you never worked on a large project with thousands of components and dozens of major chips?