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4-channel I2C-safe Bi-directional Logic Level Converter - BSS138
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

4-channel I2C-safe Bi-directional Logic Level Converter - BSS138

by boamac on Sun Mar 24, 2013 8:10 pm

I'm having an issue with the 4-channel level converter, While my own circuit
works with the arduino, the one i purchased from you does not seem to be
working. The arduino is not registering with the rpi on i2c as it does with
mine. I have it connected as follows:

LV - 3v3
hv - 5v
a1 - RPi sda
a2 - RPi scl
b1 - Ard sda
b2 - Ard scl
gnd - on both sides tied together and also tied to ground.

IS this a misconfiguration on my part or a faulty part.

boamac
 
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Re: 4-channel I2C-safe Bi-directional Logic Level Converter - BSS138

by adafruit_support_bill on Mon Mar 25, 2013 6:08 am

While my own circuit
works with the arduino, the one i purchased from you does not seem to be
working.

What circuit are you using? The BSS138 FETs with 10K pullups are a little on the sluggish side as mentioned in the product description and may not work well at higher speeds.

For Arduino to Pi communication, you probably don't need the converter. The Pi has 3.3v pullups and the Arduino has none.

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Re: 4-channel I2C-safe Bi-directional Logic Level Converter - BSS138

by boamac on Mon Mar 25, 2013 4:06 pm

I'm using a custom mosfet circuit i made, but i'm using it between the pi and arduino since i will likely want to send and receive both ways and would rather not fry the pi as i'm given to understand it can't handle more than 3.3v

boamac
 
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Re: 4-channel I2C-safe Bi-directional Logic Level Converter - BSS138

by adafruit_support_bill on Mon Mar 25, 2013 4:40 pm

i will likely want to send and receive both ways and would rather not fry the pi

The way i2c works, no device drives the line high. They only drive it low. To send a "HIGH" signal, the pin is switched to high-impedence mode and the pullups pull it high. With only 3.3v pullups on the bus, the line will never go higher than 3.3v.

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Re: 4-channel I2C-safe Bi-directional Logic Level Converter - BSS138

by boamac on Mon Mar 25, 2013 7:00 pm

Irregardless of whether it's need, as a level converter, it should work that same a custom built one. That being said, it's not working and this is my concern.

boamac
 
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Re: 4-channel I2C-safe Bi-directional Logic Level Converter - BSS138

by zener on Mon Mar 25, 2013 7:36 pm

What is the speed of your data? It may be beyond the ability of the part, but there isn't a limit specified.

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Re: 4-channel I2C-safe Bi-directional Logic Level Converter - BSS138

by adafruit_support_bill on Mon Mar 25, 2013 8:28 pm

What is the speed of your data? It may be beyond the ability of the part

Yes. As I noted earlier, the product description warns about that. What value pullups does your custom circuit use?
The 10K's do make the interface a little more sluggish than using a TXB0108 or 74LVC245 so we suggest checking those out if you need high-speed transfer.

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Re: 4-channel I2C-safe Bi-directional Logic Level Converter - BSS138

by boamac on Mon Mar 25, 2013 9:09 pm

I'm using 2 10k resistors on each side and irf50 n-channel mosfets. Using those circuits laid out in this layout:

https://www.circuitlab.com/circuit/2k39 ... duino-uno/

i2c is running at 9600

The circuit works correctly. Using the 4-channel i received from it, it does not work at all. I doubt speed is the issue in this case. When i say it doesn't work, i mean that the Arduino is not even seen by the Raspberry pi, it's not sluggish or slow, it just doesn't exist to the Raspberry pi.

I'll check the components and Solder joints and make sure it's not something simple, but as it is, the board is failing.

boamac
 
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Re: 4-channel I2C-safe Bi-directional Logic Level Converter - BSS138

by adafruit_support_bill on Mon Mar 25, 2013 9:11 pm

If you contact support@adafruit.com with a link to this thread we can send you a replacement.

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Re: 4-channel I2C-safe Bi-directional Logic Level Converter - BSS138

by boamac on Tue Mar 26, 2013 6:42 pm

Please disregard this, i feel like quite the fool, i went back and reflowed the pins and it's working. Just goes to show that no matter how long you've been soldering, there's always the chance you'll screw up.

boamac
 
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Please be positive and constructive with your questions and comments.