Date: Wed, 5 May 2021 21:04:10 -0700 From: Elwood Downey <elwood.downey@gmail.com> To: freebsd-arm@freebsd.org Subject: Re: GPIO pullups not working -- SOLVED (or at least understood) Message-ID: <CAL98DL4SWGA%2Bb%2BvtfDhLna2TEmwfKnLZ2-E7-CgC%2BPvL08MvXw@mail.gmail.com> In-Reply-To: <CAL98DL70Zt7oV57MwNrOKakXPieu5smjR%2BNJdkUUHcBjiwdvTg@mail.gmail.com> References: <CAL98DL70Zt7oV57MwNrOKakXPieu5smjR%2BNJdkUUHcBjiwdvTg@mail.gmail.com>
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A little followup to my own post.... I have done some bare metal programming on the broadcom devices in the past so I thought I'd try to find the relevant freebsd driver. The closest one I could find in /usr/src is for the bcm2835. This chip was used on the Pi3. The Pi4 uses the bcm2711 which, in their infinite wisdom, uses a different register set and protocol for controlling the gpio pullups. Code for the 2835 executing on a 2711 is harmless but does nothing, in agreement with my observations. Then I found bcm2835_gpio.c which I must say is beautifully written. I'm tempted to tweak a few lines in bcm_gpio_set_pud() but I'd have to figure out how to rebuild the kernel which I will leave for another day. Not a big deal, until the 2711 is supported I'll just use an external pullup. All the best, On Tue, May 4, 2021 at 11:24 AM Elwood Downey <elwood.downey@gmail.com> wrote: > Hello all; > > Using RELEASE-13 on Raspberry Pi 4 I can not seem to engage GPIO input > pullups. Doing so should cause an input not connected to anything to read > high but it always reads low. Connecting the pin to 3.3V does read hi so I > know the pin is working correctly as an input, just that the pullup is not > connecting. > > I configure the pin as follows: > > freebsdpi# gpioctl -c 21 PU IN > freebsdpi# gpioctl -l | grep 21 > pin 21: 0 pin 21<IN,PU> > freebsdpi# sysctl dev.gpio.0.pin.21.function > dev.gpio.0.pin.21.function: input > > # test with pin disconnected > freebsdpi# gpioctl 21 > 0 > > Now connecting to 3.3V: > freebsdpi# gpioctl 21 > 1 > > Installing a microSD with Raspbian Buster in the same Pi, I can repeat the > above using their tools and the pullup works as expected, so I know the > hardware is fine. > > Any help appreciated, advTHANKSance > > Elwood Downey > Tucson AZ >
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