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Re: I2C core questions (Avalon, SOPC)
by tadorta
::
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Hello Thomas,
I'm using the i2c_master_top core in my project, and I can tell you
that it works properly.
The bug exists, is "sda_pad_i <= sda"
To use I2C bus you need to put external pull up resistors, to force
weak high level.
To control the i2c_master_top core you need a Wishbone master. I built
my own WB master in VHDL for this propose. I don´t know if you can
control it with NIOS via avalon, I suppose u have to build some kind
of interface between wishbone and avalon.
If you have some specific question about code tell me
Taho
tadorta@...
----- Original Message -----
From: Thomas Winkler<tc@t...>
To:
Date: Thu Feb 7 09:57:08 CET 2008
Subject: [oc] I2C core questions (Avalon, SOPC)
> Hello,
>
> I'm currently working on connecting the opencores I2C master (VHDL
> version) to
> the NIOS 2 processor via the Avalon bus. I intend to run the NIOS 2
> on the
> Altera DE2 board (based on a Cyclone 2 FPGA).
> So far I've completed the following step:
> 1) Wrapper code that implements the tri-state buffers for SCL and
> SDA and
> eliminates ARST_LVL and arst_i at the toplevel (I've tied ARST_LVL
> to '0' and
> arst_i to '1').
> I've uploaded the source to
> http://www.wnk.at/tmp/i2c/i2c_master_top_avalon.vhd
> BTW: In the I2C master document there seems to be a mistake
> regarding the
> tri-state: I think the last line should be sda_pad_i <= sda;
> instead of
> scl_pad_i <= sda;"
> 2) I've create a SOPC component. The singals and itnerfaces of the
> SOPC
> component can be found at
> http://www.wnk.at/tmp/i2c/sopc_signals.png
> and
> http://www.wnk.at/tmp/i2c/sopc_interfaces.png
> I tried to stick to the information from the OC I2C FAQ. But I'm by
> no means
> an SOPC or Avalon expert - so I'd be glad if someone with more
> experience
> could have a brief look at it to tell me if it looks ok.
> 3) I've attached the I2C component to a simple NIOS 2 processor
> using SOPC
> builder (see http://www.wnk.at/tmp/i2c/sopc_nios.png). After
> generating the
> system I did a pin assignment in the Quartus II software. I
> assigned SCL and
> SDA to pins of the expansion header of the DE2 board.
> What kind of surprised me was that SCL and SDA are recongized as
> pure output
> pins by quartus although they are marked as bidirectional in SOPC
> builder.
> The pin assignment can be seen at:
> http://www.wnk.at/tmp/i2c/pin_assignment.png
> After downloading the system to the DE2 board i measured the signal
> levels of
> the SCL and SDA pins on the DE2 board. The SCL pin is at 0V and the
> SDA pin
> is at 1.2V.
> I'm not sure if this is the expected behavior. In the pin
> assignment editor
> the pins are set to 3.3V (TTL).
> What I also didn't fully understand yet are the pull-ups. Do I have
> to add
> external pull-up resistors (connecting SCL and SDA to 3.3V) or is
> that
> somehow done on the board / in the FPGA?
> I'm anything but an digital design / FPGA expert but I have some
> basic
> knowledge of VHDL and realted topics. Therefore I'd appreciate any
> help I can
> get to make this work. In case of success I'd be happy to
> contribute to this
> project by making the SOPC I2C component available for download.
> Thank you very much,
> --
> Thomas Winkler
> tc at tomwinkler.net
>
>_______________________________________________
http://www.opencores.org/mailman/listinfo/cores
I'm using the i2c_master_top core in my project, and I can tell you
that it works properly.
The bug exists, is "sda_pad_i <= sda"
To use I2C bus you need to put external pull up resistors, to force
weak high level.
To control the i2c_master_top core you need a Wishbone master. I built
my own WB master in VHDL for this propose. I don´t know if you can
control it with NIOS via avalon, I suppose u have to build some kind
of interface between wishbone and avalon.
If you have some specific question about code tell me
Taho
tadorta@...
----- Original Message -----
From: Thomas Winkler<tc@t...>
To:
Date: Thu Feb 7 09:57:08 CET 2008
Subject: [oc] I2C core questions (Avalon, SOPC)
> Hello,
>
> I'm currently working on connecting the opencores I2C master (VHDL
> version) to
> the NIOS 2 processor via the Avalon bus. I intend to run the NIOS 2
> on the
> Altera DE2 board (based on a Cyclone 2 FPGA).
> So far I've completed the following step:
> 1) Wrapper code that implements the tri-state buffers for SCL and
> SDA and
> eliminates ARST_LVL and arst_i at the toplevel (I've tied ARST_LVL
> to '0' and
> arst_i to '1').
> I've uploaded the source to
> http://www.wnk.at/tmp/i2c/i2c_master_top_avalon.vhd
> BTW: In the I2C master document there seems to be a mistake
> regarding the
> tri-state: I think the last line should be sda_pad_i <= sda;
> instead of
> scl_pad_i <= sda;"
> 2) I've create a SOPC component. The singals and itnerfaces of the
> SOPC
> component can be found at
> http://www.wnk.at/tmp/i2c/sopc_signals.png
> and
> http://www.wnk.at/tmp/i2c/sopc_interfaces.png
> I tried to stick to the information from the OC I2C FAQ. But I'm by
> no means
> an SOPC or Avalon expert - so I'd be glad if someone with more
> experience
> could have a brief look at it to tell me if it looks ok.
> 3) I've attached the I2C component to a simple NIOS 2 processor
> using SOPC
> builder (see http://www.wnk.at/tmp/i2c/sopc_nios.png). After
> generating the
> system I did a pin assignment in the Quartus II software. I
> assigned SCL and
> SDA to pins of the expansion header of the DE2 board.
> What kind of surprised me was that SCL and SDA are recongized as
> pure output
> pins by quartus although they are marked as bidirectional in SOPC
> builder.
> The pin assignment can be seen at:
> http://www.wnk.at/tmp/i2c/pin_assignment.png
> After downloading the system to the DE2 board i measured the signal
> levels of
> the SCL and SDA pins on the DE2 board. The SCL pin is at 0V and the
> SDA pin
> is at 1.2V.
> I'm not sure if this is the expected behavior. In the pin
> assignment editor
> the pins are set to 3.3V (TTL).
> What I also didn't fully understand yet are the pull-ups. Do I have
> to add
> external pull-up resistors (connecting SCL and SDA to 3.3V) or is
> that
> somehow done on the board / in the FPGA?
> I'm anything but an digital design / FPGA expert but I have some
> basic
> knowledge of VHDL and realted topics. Therefore I'd appreciate any
> help I can
> get to make this work. In case of success I'd be happy to
> contribute to this
> project by making the SOPC I2C component available for download.
> Thank you very much,
> --
> Thomas Winkler
> tc at tomwinkler.net
>
>
http://www.opencores.org/mailman/listinfo/cores
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