Date: Thu, 22 May 2014 19:21:47 +0300 From: "Sulev-Madis Silber (ketas)" <madis555@hot.ee> To: Ian Lepore <ian@FreeBSD.org> Cc: "freebsd-arm@freebsd.org" <freebsd-arm@FreeBSD.org> Subject: Re: BBB MMC / SD detection instability with U-Boot 2014.04 (CPU 1GHz) Message-ID: <537E241B.6060602@hot.ee> In-Reply-To: <1400770385.1152.233.camel@revolution.hippie.lan> References: <CADH-AwGb36EUknNofdch1Q4Pn8GAN%2BEp9SdiJ_f7Q2v9e4kW1g@mail.gmail.com> <20140522.204656.144162099.toshi@ruby.ocn.ne.jp> <1400765234.1152.224.camel@revolution.hippie.lan> <20140522.231553.186386229.toshi@ruby.ocn.ne.jp> <CAB=2f8xyzLQpTQgwc8EHh-_A-0HV_H3w_7uW_RAYXM8X_Q02MA@mail.gmail.com> <1400770385.1152.233.camel@revolution.hippie.lan>
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On 2014-05-22 17:53, Ian Lepore wrote: > On Thu, 2014-05-22 at 11:34 -0300, Luiz Otavio O Souza wrote: >> Just picking one email to reply... >> >> This is probably unrelated, but i can consistently corrupt my SD Card >> data if i connect (and use) a very small R/C servo (the 9g ones, used >> on foam planes) to the 3.3v on the expansion headers. >> >> I'm not sure if it is because of noise or the power consumption, but >> looks like the BBB is really picky about the power conditions here. >> >> Connecting the servo to the VDD_5V on the same header makes the problem go away. >> >> So be careful about what you connect on your boards :) >> > > It looks like the 3v3b rail comes off a 500mA LDO and is already > powering several of the onboard chips (including eMMC and at least part > of the ethernet phy), so it may be power consumption. > > -- Ian > > > _______________________________________________ > freebsd-arm@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-arm > To unsubscribe, send any mail to "freebsd-arm-unsubscribe@freebsd.org" > It's somehow related... Why does the ADC driver discard the input #8 (measures VDD_3V3B)? I don't know why exactly board designers decided to connect it there (instead of PMIC ADC mux or just header), but I have some ideas why and what to do with it. I can patch it locally too, if absolutely required. Maybe you could measure LDO status that way a bit. That of course doesn't mean you should run motors off IC power rails. Voltage measurements can't really help there. Even shared GND can sometimes be problem...home | help
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