I2C on amd64

SirDice said:
Use a logic level converter to convert the 3.3V signals to 5V TTL and vise versa. You could drive a 5V TTL input with a 3.3V output (3.3V is above the logic '1' minimal voltage of TTL) but driving a 3.3V input with a 5V TTL signal is likely going to blow something up (unless the chip is 5V tolerant but I doubt that).

The TXS0108E is useful. You can buy these on breakout boards. They're not that expensive.


Click to expand...
The I2C device which I want to use with this are 5 V capable, for example this one:

I will start my experiments with this ADS1115, it works very well on a BeagleBone Black at a 3.3 V level, however, I had this working already behind an ADUM1251, which is an I2C isolator.

With this in place, the BBB worked at 3.3 V and the other side at 5 V (actually ±2.5 V) with the ADS1115. This is a perfect way to make an uniploar (0 ... VDD) ADC working bipolar (-VDD/2 ... +VDD/2).
 
Regarding level shifters it is possible to build a bidirectional one by 2x transistors in common base configuration. As far as I remember you can find it by searching for "Nokia" and "Level shifter". I did not find a PDF on my PC but I have a print out somewhere which I can scan and send you if you are interested. Of course a dedicated IC is easier to use.

About the 74LS05 it seems to be a circuit which connects SDA and SCL to two different pins per signal. It will be a matter of the driver to combine them to I2C. Just a super minor, it might be safe to connect pin 13 with pin 14. Then the input of U1F is not floating.
 
chrbr said:
Regarding level shifters it is possible to build a bidirectional one by 2x transistors in common base configuration. As far as I remember you can find it by searching for "Nokia" and "Level shifter". I did not find a PDF on my PC but I have a print out somewhere which I can scan and send you if you are interested. Of course a dedicated IC is easier to use.

About the 74LS05 it seems to be a circuit which connects SDA and SCL to two different pins per signal. It will be a matter of the driver to combine them to I2C. Just a super minor, it might be safe to connect pin 13 with pin 14. Then the input of U1F is not floating.
Click to expand...
Have a look at lpbb(4). I tried to reproduce exactly the scheme which is said to work with the bit banging kernel module.

PS:
Pin 13 of JPP1 is connected to GND and hence to pin 7 of U1 (as it is in said man file).
 
chrbr said:
Wow, I have not expected a schematics in ASCII art. If that is supported it is perfect :).
...
Click to expand...

I hope, I will see this soon, and I will report the results here.

chrbr said:
...
Regarding pin 13 I meant the input of the spare inverter section U1F. It is adjacent to pin14 which is its supply pin.
Click to expand...

Aah, OK, I will do this. I left it as is, because it was not even present in Phillip's original ASCII art scheme.
 
I finished the parallel port to I2C bit banging circuit on a tiny prototype board - it is not as nice as a real pcb would have been, like the 3D image in my other post, however, I soldered and checked everything very carefully, and I am sure that this part should work. Into the I2C slot, I plugged in a breakout board featuring a TI-I2C-ADC (ADS1115) -- see the pictures below.

Unfortunately, everything was to no avail, since the lpbb(4) kernel module seems to have been broken for at least 14 years.
https://lists.freebsd.org/pipermail/freebsd-stable/2008-March/041468.html

Well, so it is, this project goes back into the drawer, until I find some time to look at the lpbb module -- don't hold your breath.

IMG_1310.JPG
IMG_1309.JPG
IMG_1313.JPG
 
Here is the message from the FT232H from my first post that arrived in the mail.
Code: 
Mar 12 06:04:51 E6420 kernel: ugen1.6: <FTDI FT200X USB I2C> at usbus1
Mar 12 06:04:51 E6420 kernel: uftdi0 on uhub3
Mar 12 06:04:51 E6420 kernel: uftdi0: <FT200X USB I2C> on usbus1

Looking here I need to switch it from RS232 mode to Open Drain mode with thier Windows utility.
github.com

GitHub - kkrizka/adafruitft232h_i2c_adapter: An I2C adapter for the FT232H breakout board by Adafruit.

An I2C adapter for the FT232H breakout board by Adafruit. - kkrizka/adafruitft232h_i2c_adapter
github.com github.com
 
Phishfry said:
Here is the message from the FT232H from my first post that arrived in the mail.
Code: 
Mar 12 06:04:51 E6420 kernel: ugen1.6: <FTDI FT200X USB I2C> at usbus1
Mar 12 06:04:51 E6420 kernel: uftdi0 on uhub3
Mar 12 06:04:51 E6420 kernel: uftdi0: <FT200X USB I2C> on usbus1
Click to expand...
I purchased a similar module which arrived today. It's detected by FreeBSD, but there's possibly one big deal breaker which I missed earlier:

From https://electronics.stackexchange.com/questions/420673/usb-to-i2c-for-a-beginner : "T200XD is a I2C slave chip, so it cannot be used as a master to talk to another I2C slave [...]"

I was expecting it to be a master. The FreeBSD i2c subsystem also seems to expect the hardware acts as a master. Not sure how useful a computer USB<-> I2C slave setup would be, perhaps to emulate a sensor?

I also purchased a CH341 board, which has both serial and I2C pins, but it seems to be supported by FreeBSD only as a serial port (uchcom device); when switched to I2C mode via the board header, it shows up as a ugen device.
 
Didn't buy that one unfortunately. Revamped my list.
The price increased now on those alot too. More than inflation...

I probably have ADD as I go in wild swings from project to project and never finishing anything.
If I machined like that I wouldn't get paid.
 
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