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>
next in thread | previous in thread | raw e-mail | index | archive | help
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...
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?537E241B.6060602>