| Electronics > Microcontrollers |
| Why the STM32L152 Boot0 pin needs a pulldown (and a capacitor) |
| << < (4/5) > >> |
| peter-h:
OK, an ELT / PLB / EPIRB. But why reinvent the wheel when everybody else is already dealing with on-board RF in this way (mobile phones, etc) and that is only 400mW max power. The problem is that you never quite know just how close you are to the CPU circuit falling over due to EMC. |
| thm_w:
--- Quote from: peter-h on December 28, 2024, 09:42:33 am ---Nobody is going to be there holding that probe when the product is in the field and next to some other gear :) --- End quote --- Thats what metal shielding (which you pointed out) and EMI testing is for. The probe was to detect self generated on board interference. --- Quote from: ocelot on December 28, 2024, 03:20:07 pm ---And once the BOOT0 PCB error was fixed with a capacitor by the pin, that was no longer a problem - the reflected impedance blip from the ADC was measurable though. --- End quote --- ok still no mention of the pull down resistance. |
| glenenglish:
@ ocelot. Suggest you build, buy or borrow a TEM cell . This is an excellent method of testing EM immunity in a methodical and reproducable way. https://www.tekbox.com/tem_cells/ they are quite affordable. for your apps, get the 2nd big one, TBTC2 that's a good size for what you are working on. As a side bar, I would be testing up to 50V/M minimum . this is approx a 5W 440 MHz portable radio at 20cm, give or take. ideally go to 80 V/M (10cm) if you think this is likely. work through a range of orientations. 440MHz portable radios often have quarter wave antennas (17cm long) so they're not too far from the truth with ERP. Lower frequency (~ 150 MHz) portable radio/antennas can vary over 12dB depending on their environment... hence use the TEM cell.... I found quite alot of equipment fine at 400 MHz but sensitive at 70 MHz.. However the surprises come with trace and board resonances, which is why you need to sweep over a large frequency range , the DUT in a TEM cell etc. One of the reasons cellphones have lots of shielding is the proximity of the receiver antenna to the electronics. Peter-h you are not an RF person by any stretch so why do you keep posting on this providing misleading information ? you say "The problem is that you never quite know just how close you are to the CPU circuit falling over due to EMC." no, wrong. You do testing. That's what we do. |
| peter-h:
--- Quote ---no, wrong. You do testing. That's what we do. --- End quote --- I was right - you are an EMC lab! ;) Actually, no, your testing checks that it works. It doesn't check how close it is to falling over. These sorts of products need to be heavily over-engineered. --- Quote ---One of the reasons cellphones have lots of shielding is the proximity of the receiver antenna to the electronics. --- End quote --- I think you mean the transmitter antenna ;) |
| glenenglish:
No, I really did mean the receiving antenna. No, I am not an EMC lab. Of stuff we build, we do precompliance in house. No, "These sorts of products need to be heavily over-engineered." no- that just leads to a uncompetetive device in the market. |
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