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Analysis done by Denis Kalashnikov: It seems that some ROS versions on some routerboard models have this bug: after silence boot (no output to uart, no beeps) beeper clicks when wireless traffic is. https://forum.mikrotik.com/viewtopic.php?f=3&t=92269 https://forum.mikrotik.com/viewtopic.php?t=63399 From these links: 1) Hello, I have RB951G-2HnD and I noticed strange thing when I loaded the device with some wireless traffic it produced strange sound - like hissing, fizzing etc. 2) Same problem still on 6.33, with silent boot enabled I hear buzzing noise on wireless load. 3) The sound is fixed in v5.19, it was a bug that caused beeper to make clicks. It also got fixed in RouterOS: * What's new in 5.19 (2012-Jul-16 10:51): fix ticking sound on RB411UAHL; * What's new in 6.38.3 (2017-Feb-07 09:52): rb3011 - fixed noise from buzzer after silent boot; I've checked with an oscilloscope that: * When on the ssr beeper pin is 0, on the beeper itself is 1 (~5V), and when on the ssr beeper pin is 1, on the beeper is 0 The beeper doesn't consume power, so 1 should be a default/idle value for the ssr beeper pin). * When there is wireless traffic (ping packets) in the background and the beeper clicks, I see pulses on the beeper itself, but no pulses on the ssr beeper pin (Q5 pin of 74hc595). When I manually toggle the ssr beeper pin I see pulses on both. So, it is likely that the phantom beeper clicks are caused by the EMI. Suggested-by: Denis Kalashnikov <denis281089@gmail.com> Reviewed-by: Sergey Ryazanov <ryazanov.s.a@gmail.com> Signed-off-by: Koen Vandeputte <koen.vandeputte@ncentric.com> |
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