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RaspberryPi 3 Model B+ and I2C issue

Teemu Ahola, Nokia
Posted 7 years ago

Hello,

I have been struggling with SenseHAT and Mathematica. First Mathematica was not able to find SenseHAT at all even than I followed I2C setup guide but eventually after adding following line to /boot/config.txt I was able to make some progress:

dtparam=i2c0=on

After that there is two i2c buses in the system:

pi@raspberrypi:~ $ ls -l /dev/i2c-*
crw-rw---- 1 root i2c 89, 0 Aug 30 21:34 /dev/i2c-0
crw-rw---- 1 root i2c 89, 1 Aug 30 21:34 /dev/i2c-1

However Mathematica reports variety I2C errors:

pi@raspberrypi:~ $ wolfram
Wolfram Language 11.3.0 Engine for Linux ARM (32-bit)
Copyright 1988-2018 Wolfram Research, Inc.

In[1]:= sensehat = DeviceOpen["SenseHAT"]                                                               
Out[1]= DeviceObject[{SenseHAT, 1}]
In[2]:= DeviceRead[sensehat, "Temperature"]                                                             
DeviceWrite::unknownMRAAWriteError: An unknown error occured writing to the I2C bus.
DeviceWrite::unknownMRAAWriteError: An unknown error occured writing to the I2C bus.
DeviceWrite::unknownMRAAWriteError: An unknown error occured writing to the I2C bus.
General::stop: Further output of DeviceWrite::unknownMRAAWriteError
     will be suppressed during this calculation.
Out[2]= 42.4979 degrees Celsius

when investigating further linux journal it seems that libmraa (presumably of Mathematica MRAALink) tries to use I2C-0 bus:

Aug 30 21:38:05 raspberrypi libmraa[1037]: libmraa version v1.6.1 initialised by user 'pi' with EUID 100
Aug 30 21:38:05 raspberrypi libmraa[1037]: libmraa initialised for platform 'Raspberry Pi Model B Rev 1'
Aug 30 21:38:05 raspberrypi libmraa[1037]: i2c_init: Selected bus 0
Aug 30 21:38:22 raspberrypi libmraa[1037]: i2c0: write: Access error: Remote I/O error
Aug 30 21:38:22 raspberrypi libmraa[1037]: i2c0: write: Access error: Remote I/O error

However as far as I can tell the SenseHAT is in i2c bus 1. So I removed "dtparam=i2c0=on" and after reboot added symbolic link for i2c-0 from i2c-1:

pi@raspberrypi:/ $ ls -la /dev/i2c-*
lrwxrwxrwx 1 root root    10 Aug 30 21:43 /dev/i2c-0 -> /dev/i2c-1
crw-rw---- 1 root i2c  89, 1 Aug 30 21:41 /dev/i2c-1

and tried again SenseHAT in Mathematica which seems to work now:

pi@raspberrypi:/ $ wolfram
Wolfram Language 11.3.0 Engine for Linux ARM (32-bit)
Copyright 1988-2018 Wolfram Research, Inc.

In[1]:= sensehat = DeviceOpen["SenseHAT"]                                                               
Out[1]= DeviceObject[{SenseHAT, 1}]
In[2]:= DeviceRead[sensehat, "Temperature"]                                                             
Out[2]= 38.9896 degrees Celsius

So for me it looks that Matkematica uses wrong I2C bus at least in this particular model:

pi@raspberrypi:/dev $ cat /proc/device-tree/model 
Raspberry Pi 3 Model B Plus Rev 1.3

pi@raspberrypi:/ $ cat /etc/os-release 
PRETTY_NAME="Raspbian GNU/Linux 9 (stretch)"
NAME="Raspbian GNU/Linux"
VERSION_ID="9"
VERSION="9 (stretch)"
ID=raspbian
ID_LIKE=debian
HOME_URL="http://www.raspbian.org/"
SUPPORT_URL="http://www.raspbian.org/RaspbianForums"
BUG_REPORT_URL="http://www.raspbian.org/RaspbianBugs"

I think this should be fixed to Mathematica.
POSTED BY: Teemu Ahola
18 Replies
Sort By:
Arun Sharma
Arun Sharma
Posted 7 years ago

Hi Brett,

Were you able to resolve these issues? If so, could you please provide a set of instructions that could be used to set up the SenseHAT.

Thanks,
POSTED BY: Arun Sharma

We've found the root of the issue and, since a new Pi board has just been released, we've also added functionality for that to the relevant code. This package is in testing now and I'll post a message here as soon as it's publicly available.
POSTED BY: Brett Haines
Teemu Ahola
Teemu Ahola, Nokia
Posted 7 years ago

Sounds good.
POSTED BY: Teemu Ahola

Teemu,

I want to apologize again for the long delay in getting this fixed.

Last night we published a new version of MRAALink that works with the two latest models of Pi (the 3B+ and the 3A+). If your Pi is connected to the internet you can install it using the following code:

PacletFindRemote["MRAALink", "UpdateSites"->True]
PacletUpdate["MRAALink"]
RebuildPacletData[]

This should list 11.3.4 as the new version number for MRAALink. Please let me know if you have any other issues.
POSTED BY: Brett Haines
Teemu Ahola
Teemu Ahola, Nokia
Posted 6 years ago

Hi,

That's OK. I have been using symbolic link as a workaround. I will try out soon this new version.

Teemu
POSTED BY: Teemu Ahola
Updating Name
Updating Name
Posted 6 years ago

Hi,

Seems to be working. Thanks!

Teemu
POSTED BY: Updating Name
Updating Name
Updating Name
Posted 6 years ago

Hello Arun,

I want to apologize again for the long delay in getting this fixed.

Last night we published a new version of MRAALink that works with the two latest models of Pi (the 3B+ and the 3A+). If your Pi is connected to the internet you can install it using the following code:

PacletFindRemote["MRAALink", "UpdateSites"->True]
PacletUpdate["MRAALink"]
RebuildPacletData[]

This should list 11.3.4 as the new version number for MRAALink. If you have any issues with it please don't hesitate to message me!
POSTED BY: Updating Name

Thanks a lot for posting the solution. I will try it out soon.

POSTED BY: Arunkumar Sharma
POSTED BY: Ken-ichi Tozaki

Mr. Tozaki,

You should convert the bus number from hexadecimal 2a to the decimal 42. This is because the function is expecting an integer rather than a hex string. Could you try this?
POSTED BY: Brett Haines

Dear Mr. Brett Haines,

Thank you for your reply. I tried the change from "2a" to "42" as follows; -----------------------------

In[1]:= dev=DeviceOpen["I2C",42]  as,                                              

StringForm::sfr: 
   Item 2 requested in "The module `1` is not loaded and needs to be loaded.
      Load it by adding the line " `2` " to the file "/etc/modules" with a text
      editor and reboot." out of range; 1 items available.
DeviceOpen::needModule: 
   The module spidev is not loaded and needs to be loaded. Load it by adding the
     line " `2` " to the file "/etc/modules" with a text editor and reboot.

StringForm::sfr: 
   Item 2 requested in "The module `1` is not loaded and needs to be loaded.
      Load it by adding the line " `2` " to the file "/etc/modules" with a text
      editor and reboot." out of range; 1 items available.
DeviceOpen::needModule: 
   The module spi-bcm2835 is not loaded and needs to be loaded. Load it by
     adding the line " `2` " to the file "/etc/modules" with a text editor and
     reboot.

DeviceOpen::deviceTree: 
   The device tree overlay for SPI
     has not been turned on. Turn it on by editing the file "/boot/config.txt"dt
       to add the line 

     param=spi=on
                  and reboot.

Out[1]= $Failed

I have no idea to improve this situation now.

Sincerely yours, K. Tozaki
POSTED BY: Ken-ichi Tozaki
POSTED BY: Brett Haines
Teemu Ahola
Teemu Ahola, Nokia
Posted 7 years ago

Hi Brett,

I am still having problems. 

pi@raspberrypi:~ $ i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- 1c -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- UU -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- 5c -- -- 5f 
60: -- -- -- -- -- -- -- -- -- -- 6a -- -- -- -- -- 
70: -- -- -- -- -- -- -- --                         
pi@raspberrypi:~ $ wolfram
Wolfram Language 11.3.0 Engine for Linux ARM (32-bit)
Copyright 1988-2018 Wolfram Research, Inc.

In[1]:= dev=DeviceOpen["I2C",92]                                                

DeviceOpen::mraaInitFailure: Failed to initialize the MRAA library

Out[1]= $Failed

I checked journalctl and I see this error:

Sep 12 20:44:36 raspberrypi libmraa[843]: libmraa version v1.6.1 initialised by user 'pi' with EUID 1000
Sep 12 20:44:36 raspberrypi libmraa[843]: libmraa initialised for platform 'Raspberry Pi Model B Rev 1' of type 5
Sep 12 20:44:37 raspberrypi libmraa[843]: i2c_init: Selected bus 0
Sep 12 20:44:37 raspberrypi libmraa[843]: i2c: Device not initialized
Sep 12 20:44:37 raspberrypi libmraa[843]: i2c: If you run a kernel >=3.18 then you will have to add dtparam=i2c0=on to /boot/config.txt and reboot

Perhaps this is the reason that the libmraa is still trying to use i2c bus 0.

Teemu
POSTED BY: Teemu Ahola

Teemu, the Sense HAT should only be communicating through i2c-1, so having i2c-0 isn't necessary at all. Also, the Pi 3B and 3B+ both should have i2c-bcm2835 enabled, not i2c-bcm2708. The latter was used in older models of the Pi. I will make sure the page you linked gets updated accordingly.

In the mean time, I will continue trying to replicate your issues on my end.
POSTED BY: Brett Haines
Teemu Ahola
Teemu Ahola, Nokia
Posted 7 years ago

Hi Brett,

Ok. Thanks for your response.
POSTED BY: Teemu Ahola

I have the same worry with Mr. Teemu. I am looking for the solution. My i2c devices supported by not bcm2708 but bcm2835. I could not add bcm2708 on display of boot/config.txt. "bcm2835" is seemes to use in "audio"; therefore, "#dtparam=audio=on" may be necessary.
POSTED BY: Ken-ichi Tozaki

Hi Teemu, I'm looking into this for you now. Could you answer a couple of questions for me so I can reproduce this on my own Pi?

  1. Is the following line present in /boot/config.txt:

    dtparam=i2c_arm=on

  2. Did you enable I2C via raspi-config or the Raspberry Pi Configuration program in the applications menu?

  3. What error messages did you get before adding i2c0=on to the boot config?

Thanks,

Brett
POSTED BY: Brett Haines
Teemu Ahola
Teemu Ahola, Nokia
Posted 7 years ago

Hi Brett,

  1. Yes and no. I have had it there and I have not. In both cases I see always /dev/i2c-1 but not /dev/i2c-0 (unless dtparam=i2c0=on is there as well).
  2. I think I enabled it first by modifying the /boot/config.txt but I have also played around with the Raspberry Pi Configuration program. However I am not 100% sure which one I used first since I was trying to get SenseHAT to work and I tried so many different instructions to enable I2C so I cannot quite remember what I tried initially.

I have only one line in /etc/modules:

i2c-dev

and I think it was there already when I looked the file first time. I have also tried to add i2c-bcm2708 in to the file as instructed by the I2C Setup guide but that seems not to make any difference. Also /etc/modprobe.d/raspi-blacklist.conf is empty.
POSTED BY: Teemu Ahola
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