[beagleboard] Re: Is it easy to reduce the clock frequency on Beaglebone I2C?
Hi Chris, I did not mean to say that LINUX is not useful. But yes, I can see your point: if you have to change the I2C clock that is something different. Martin H. -- 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 beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[beagleboard] Re: Is it easy to reduce the clock frequency on Beaglebone I2C?
I freely admit that I don't know anything about LINUX. We don't use it. But why would you want to modify the device tree if I2C is running? We have I2C running with an LPC2468. All we did is putting a P8287 at each end of the line. And it works. No code modification was required. Martin H. -- 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 beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[beagleboard] Re: Is it easy to reduce the clock frequency on Beaglebone I2C?
Martin H. mart...@innomar.com wrote: [-- text/plain, encoding 7bit, charset: UTF-8, 16 lines --] I freely admit that I don't know anything about LINUX. We don't use it. But why would you want to modify the device tree if I2C is running? We have I2C running with an LPC2468. All we did is putting a P8287 at each end of the line. And it works. No code modification was required. Well, say my BBB is also my local DNS server, or maybe it runs a print server, or maybe someone else is using it to edit some files? If I have to reboot it just to change the I2C frequency it will spoil all those other things until it has rebooted. Linux (like Unix) is a proper multitasking OS and while a BBB *might* be dedicated to one task it is quite a powerful little beast and is perfectly capable of doing all the things I've listed above at the same time. The whole philosophy of having to be root to do any significant changes to the IO and of having to reboot as well is all wrong IMHO. -- Chris Green · -- 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 beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[beagleboard] Re: Is it easy to reduce the clock frequency on Beaglebone I2C?
You might like to have a look at the P82B96 data sheet. Feature: 400kHz operation over at least 20 meters of wire And you don't have to modifiy your I2C code! Martin H. Am Freitag, 29. August 2014 19:18:46 UTC+2 schrieb c...@isbd.net: I want to stretch the I2C bus to a few metres, I will use screened cable to minimise noise pick-up but this will increase the capacitive load on the bus. So, I probably need to reduce the I2C clock frequency, how easy is it to do this? I will probably use the Adafruit libraries but don't have to. -- Chris Green · -- 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 beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [beagleboard] Re: Is it easy to reduce the clock frequency on Beaglebone I2C?
Just change the speed in board file or in dts
i2c4 {
pinctrl-names = default;
clock-frequency = 40;
};
It is 400kHz you can change to 100kHz
or If you are using a board file
omap_register_i2c_bus(2, 400, drishti_i2c2_board_info,
ARRAY_SIZE(drishti_i2c2_board_info));
You can specify 100
I also dont see a point to reduce . You can also specify in u-boot as well
Kavitha
On Mon, Sep 1, 2014 at 12:17 PM, Martin H. mart...@innomar.com wrote:
You might like to have a look at the P82B96 data sheet.
Feature:
400kHz operation over at least 20 meters of wire
And you don't have to modifiy your I2C code!
Martin H.
Am Freitag, 29. August 2014 19:18:46 UTC+2 schrieb c...@isbd.net:
I want to stretch the I2C bus to a few metres, I will use screened
cable to minimise noise pick-up but this will increase the capacitive
load on the bus. So, I probably need to reduce the I2C clock
frequency, how easy is it to do this? I will probably use the
Adafruit libraries but don't have to.
--
Chris Green
·
--
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 beagleboard+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
--
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 beagleboard+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
Re: [beagleboard] Re: Is it easy to reduce the clock frequency on Beaglebone I2C?
... and the P82B71 ... Martin H. -- 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 beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[beagleboard] Re: Is it easy to reduce the clock frequency on Beaglebone I2C?
Martin H. mart...@innomar.com wrote: [-- text/plain, encoding quoted-printable, charset: UTF-8, 31 lines --] You might like to have a look at the P82B96 data sheet. Feature: 400kHz operation over at least 20 meters of wire And you don't have to modifiy your I2C code! Actually I have some P82B715PN on order, an older device but similar and available in DIP so easier for me to use. However it would still be nice to be able to slow the bus down rather more easily than modifiying the device tree. -- Chris Green · -- 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 beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[beagleboard] Re: Is it easy to reduce the clock frequency on Beaglebone I2C?
The I2C protocol allows any slave device on the bus to 'stretch' the pulse for as long as it wants by holding SCL low (in Standard mode, and Fast mode, but not High-speed mode). This can slow the clock rate arbitrarily. It's explained in specification: I²C-bus Specification, Version 3.0 (Rev. 03 - 19 June 2007) this is the I2C reference! http://www.nxp.com/documents/user_manual/UM10204.pdf You can do this fairly easily 'bit twiddling' a couple of IO pins on a microcontroller. It's an interesting programming exercise! Max -- 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 beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
