From a58bcc9e673db3c6aa39f2089d216d51c8356418 Mon Sep 17 00:00:00 2001 From: Koen Vandeputte Date: Mon, 28 Jun 2021 10:57:21 +0200 Subject: [PATCH] ath79: mikrotik: fix beeper phantom noise on RB912 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 Reviewed-by: Sergey Ryazanov Signed-off-by: Koen Vandeputte --- .../ath79/dts/ar9342_mikrotik_routerboard-912uag-2hpnd.dts | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/target/linux/ath79/dts/ar9342_mikrotik_routerboard-912uag-2hpnd.dts b/target/linux/ath79/dts/ar9342_mikrotik_routerboard-912uag-2hpnd.dts index cc5553acda..ee2c12b4e0 100644 --- a/target/linux/ath79/dts/ar9342_mikrotik_routerboard-912uag-2hpnd.dts +++ b/target/linux/ath79/dts/ar9342_mikrotik_routerboard-912uag-2hpnd.dts @@ -107,6 +107,12 @@ gpio-export { compatible = "gpio-export"; + beeper { + gpio-export,name = "beeper"; + gpio-export,output = <1>; /* Must be 1 to avoid EMI induced clicking noise */ + gpios = <&ssr 5 GPIO_ACTIVE_HIGH>; + }; + usb_power { gpio-export,name = "power-usb"; gpio-export,output = <1>; -- 2.30.2