I2C needs pull-up resistors to work. There are no pull-up resistors on the BBB board, on I2C-2. There are some 10K pull up resistors on the MPU-9250 breakout board. So, if you disconnect the MPU-9250 breakout board when you hook up the oscilloscope, then the bus can't work. You need to bridge the SDA and SCL lines with the oscilloscope, with the MPU-9250 connected in order to see anything on the osciloscope.
I note that you are trying to run the MPU-9250 over a long cable, perhaps several feet long. I can't tell from your photos. I2C is NOT a cable protocol. It is intended for communications between ICs on the same PC board, or close together. So, I would start by getting the MPU-9250 to work with the Beaglebone using four short connecting wires, not over 6 inches (15 cm) long. I would recommend using the most recent 'release' version of Debian. ( Debian 8.6 2016-11-06 <https://debian.beagleboard.org/images/bone-debian-8.6-lxqt-4gb-armhf-2016-11-06-4gb.img.xz> ) With the MPU-9250 connected to the BBB, and booted, You should have +3.3 Volts on the Vdd pin of the MPU-9250 breakout board You should have 0 Volts on the GND pin of the MPU-9250 breakout board Both the SDA and the SCL lines should be idling at +3.3V, with no communications active. With the oscilloscope bridging the connected SDA and SCL lines, run "i2cdetect -y -r 2" You should see a lot of activity on both the SCL line and the SDA line for a fraction of a second. If you are going to remote the MPU-9250 over a cable, there are things that can be done, but get it running on short, close leads, first. --- Graham == On Friday, March 10, 2017 at 9:27:14 AM UTC-6, Graham wrote: > > If you have a current version of Debian 8, with the cape manager, > THEN I2C-2 IS ALREADY ENABLED. > IT IS ALREADY BROUGHT OUT ON P9_19 and P9_20 > Start with that one, Don't mess with I2C-1. If you touch the EEPROM on > I2C-1, you can brick the unit. It is intended for internal use. > Get your part working on I2C-2, before you start messing with other things. > > put your part on P9-19 and P9-20, then boot, then run "i2cdetect -y -r 2" > > If you wired it up right, it will be there. > > == > > On Friday, March 10, 2017 at 9:08:39 AM UTC-6, christ christ wrote: >> >> Hi Graham, >> I have been using the latest version of Debien, for three days now with >> the same result. >> On the other hand i checked with the oscilloscope the SDA and SCL lines >> are not acting like they are supposed to act (even on the default P9_19 and >> P9_20). >> >> Thought maybe they all need to be enable.Tried the following method but >> in vain (NO such file or directory is the response i'm getting) >> *To enable the I2c-1 on the BeagleBone Black Rev A, B and C:* >> >> 1. Rev A/B: Open the file /media/BEAGLEBONE/uEnv.txt in an editor >> (vim/nano) >> 2. Rec C: Open the file /boot/uboot/uEnv.txt in an editor (vim/nano) >> 3. Add the key "capemgr.enable_partno=" >> 4. Add the ports you want to enable, comma separated (BB-I2C0, >> BB-I2C1, etc) >> 5. Reboot. >> >> Am i right to say the I2c buses are not enable? or is it another proble? >> >> On Thu, Mar 9, 2017 at 4:25 PM, Graham <[email protected]> wrote: >> >>> Then it is not wired or connected correctly. >>> Put an oscilloscope on the data and clock lines and see if they are >>> doing what they are supposed to do. >>> It also looks like you are using an old version of the OS. >>> Move to Debian 8, and you should see the I2C devices on bus 2. >>> Hook the I2C Clock to P9-19. Hook the I2C data to P9-20. >>> You should not have to mess with the device tree or pin configuration. >>> Power and ground also required. >>> >>> --- Graham >>> >>> == >>> >>> On Thursday, March 9, 2017 at 6:52:04 AM UTC-6, christ christ wrote: >>>> >>>> The MPU-9250 breakout from spark fun come with pull up resistors. >>>> >>>> On 09 Mar 2017 00:42, "Graham" <[email protected]> wrote: >>>> >>>>> Something is not wired right. >>>>> Did you put pull-up resistors on the I2C lines? >>>>> --- Graham >>>>> >>>>> == >>>>> >>>>> On Wednesday, March 8, 2017 at 12:02:04 PM UTC-6, [email protected] >>>>> wrote: >>>>>> >>>>>> Hi Guys, >>>>>> >>>>>> I’m struggling to get the device address (MPU-9250). i got to the >>>>>> following stage: >>>>>> >>>>>> >>>>>> root@beaglebone:~# sudo i2cdetect -r 0 >>>>>> WARNING! This program can confuse your I2C bus, cause data loss and >>>>>> worse! >>>>>> I will probe file /dev/i2c-0 using read byte commands. >>>>>> I will probe address range 0x03-0x77. >>>>>> Continue? [Y/n] y >>>>>> 0 1 2 3 4 5 6 7 8 9 a b c d e f >>>>>> 00: — — — — — — — — — — — — — >>>>>> 10: — — — — — — — — — — — — — — — — >>>>>> 20: — — — — UU — — — — — — — — — — — >>>>>> 30: — — — — UU — — — — — — — — — — — >>>>>> 40: — — — — — — — — — — — — — — — — >>>>>> 50: UU — — — — — — — — — — — — — — — >>>>>> 60: — — — — — — — — — — — — — — — — >>>>>> 70: UU — — — — — — — >>>>>> root@beaglebone:~# sudo i2cdetect -r 1 >>>>>> WARNING! This program can confuse your I2C bus, cause data loss and >>>>>> worse! >>>>>> I will probe file /dev/i2c-1 using read byte commands. >>>>>> I will probe address range 0x03-0x77. >>>>>> Continue? [Y/n] y >>>>>> 0 1 2 3 4 5 6 7 8 9 a b c d e f >>>>>> 00: — — — — — — — — — — — — — >>>>>> 10: — — — — — — — — — — — — — — — — >>>>>> 20: — — — — — — — — — — — — — — — — >>>>>> 30: — — — — — — — — — — — — — — — — >>>>>> 40: — — — — — — — — — — — — — — — — >>>>>> 50: — — — — UU UU UU UU — — — — — — — — >>>>>> 60: — — — — — — — — — — — — — — — — >>>>>> 70: — — — — — — — — >>>>>> >>>>>> >>>>>> But even after connecting my device It is still the same (I mean it >>>>>> still doesn't show the device's address). Any advise? >>>>>> >>>>>> Thanks >>>>>> >>>>> >> -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/7db8dfb4-55c0-421c-bf42-edace4f2d409%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
