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While I am a novice, I am learning & appreciate feedback if what I am writing is incorrect.
1. The Tx lines are bidirectional. HUGE selling point & important for people using protocols like I2C. The Rx lines are unidirectional; only 5 to 3.3v
2. The Rx lines are not designed well for two reasons:
a) The resistors to generate a 3.3v output low side should be 10k R1 and ~20k R2. As is, the two 10k resistors split the voltage 50% resulting in approx 2.5v low side. This is outside the acceptable window for many 3.3v part like the LIS302DL sold on this site.
b) The two grounds on the breakout are common to each other. If the two ground were NOT common, then a user likely myself could be another resistor in series with the R2 on the breakout to adjust the low output voltage on each channel. Since however, they are common this is not easily possible because now current can flow between channels between the internal R2 and an external R2 in series.
I recommend posting portions of all the above for the benefit of your customers. And consider 2 for a future rev of the breakout.

Hi, and thanks for all the good work.
One question on this logic level converter:
If I want to use this to connect a 5V processor to a 3.3V I2C sensor, can I connect one pin of the processor to the SDA pin of the sensor with both a TXI-TXO and a RXO-RXI line in parallel, and then switch that processor pin from input to ouput as required?
If not, what do you recommend I do?

The example table in the breakout schematic has a column LV. This leads the reads to believe that LV has some affect on the Max output. It doesn’t. Its not even connected to the circuit. I recommend removing that column for clarity.

Works great, But Really small and easy to lose! (But that’s just me)

I’d love to see a Ti TXS0104/108 breakout variant of this board…

If you’re working with up above about 1MHz clocks, watch out for those resistor dividers. They’ll attenuate your signal.

Why not just make a breakout board for the TI TXB0108 and/or TXS0108E? 8 Bidirectional level shifting lines, and the chips are only $2 each.

Works great with the BOB-00199 and a DB-25 for a USB to Serial break out box.
The DB-25 alowed me access to all BOB-00199 and BOB-08745 ports.
I now have Lo/Hi voltage TTL, GPIO’s, serial, reset/suspend and 3.3v/5v all on the DB-25 jack.
You wont find a USB to RS-232 converter in any big box store that can give this kind of flexibility.
I would have liked two through holes (redundant) for each connection.
This would give a little bit more flexibility in some situations.
Not a big deal and most of the time this wouldn’t be needed, just nice to have…

Neat product.
Perhaps add a 3.3V regulator footprint. I am using the board between a LOCOSYS GPS unit and a 5V PIC and currently have two diodes to get about 3.8V from the 5V line – not ideal.

So could I use this to boost the 3.3V digital out from an Arduino mini pro to 5V and then drive the TTL in on the SN754410 h-bridge?

The description is inaccurate. It reads, “A digital one going into the RXI pin on the 5V side will show up on the RXO pin on the 3.3V side as 3.3V.” In fact, a digital one going into the RXI pin on the 5V side will show up on the RXO pin on the 3.3V side as 2.5V.

I’d really like to use this to Power a 3.3v circuit.
I’m guessing it will do that just fine, but is there some kinda current limit on this I should be aware of?
Everything on the page talks about communications but I really just care about power.
Would this work for that too?

This board is a great example of why SparkFun just “gets it.” You just know they’ve come across this problem themselves, got frustrated with having to solve it multiple times, and came up with a solution. Rock on, guys!

There seems to be enough question around the subject, since the tool is used mostly for I2C and UART, how about a simple couple of schematics showing the I2C connection where the bi-directional lines must be used along with another showing a connection between two UARTS (on microprocessors) and finally between a 3.3v microcontroller and teh RS232 interface to a PC/USB?
Can I assume that the board has to be viewed from the perspective of the low voltage side of the interface you are trying to make? So the TXI will hit the 3.3v TX pin while the TXO will hit the RX pin on the 5v device? Sorry for not being bright enough to figure that out on my own.

I bought two of these to convert levels between a 5v Arduino (arduimu) and a PNI micromag 3.
I did initially used the ports as suggested in the images above and it didn’t work.
After some investigation, it turned out the level of signals from Arduino(5V) toward the micromag 93.3V) where at 2.5 instead of 3.3V.
I managed to get it to work by hijacking one of the TXO connections on Arduino side to convey the Reset signal. Other SPI signals (MOSI,SCK) where fine at 2.5V.
@Sparkfun, Would be good to highlight this in the Product info as already suggested above. If ever you build a new series of converter, might be good to tune the Voltage divider to effectively output 3.3v when supplied with 5V on the High side.

Hello ,
Can this be used to interface the GM862 uart (2.8V CMOS) with an msp430 uart (3.3V) ?

How is this different than a 74LVC244 Buffer/Line Driver?

Having trouble. Trying to shift 1.8V signal to 5.0V.
Problem is, when I wire the 1.8V + GND and the 5.0V + GND, the TXI pins go high to 1.8V, and the TXO’s go high to 5.0V, even though nothing is attached to the TXI pins (TXO’s are attached to signal pin of NPN collecting from the 5.0V supply)
Any help would be appreciated.
My 5.0V supply is 1000mA,
and the 1.8V is ~ 150mA
this is the schematic of what i’m doing:
http://bit.ly/b4wghF

Hi Elif,
The problem you’re encountering, (though it’s been a while so I bet you’ve figured it out already), is that the TX lines are pulled high, (through pull-up resistors on the board), anytime that nothing is acting to pull them low. Floating inputs will go high because of this, which is the intended behavior. Pulling the TX-line low on either side will cause the other side to properly transition to a low state.
Awesomeduck,
The device you refer to only passes the signal in one direction, from the ‘A’ side to the ‘Y’ side, so it wouldn’t be useful to communicate information back the other way. Applying a signal to the ‘Y’ output side does not affect the state of the ‘A’ input associated with it.
Have a great day everyone!
~gorg0th

I am using multiple 3.3v i2c devices(slaves) connected to an arduino(master). Do i need multiple level converters or can I put one level converter between the arduino and the devices?

Finally ordered some of these, and tested the first one today. This thing is great — a real 3.3V 5V “Easy Button.” One minor quibble is the pads could be made a bit larger for ease of soldering — but I managed okay anyway. Definitely recommended.

The Schematic Document shows in the table that 5V –> 3.3V = 2.5V.

Will this voltage be enough for interfacing an xBee with Arduino?

For Level shifting on Rx and Tx lines.

Hi everyone

I would like to convert sevral signal and clock from 5v to 2.5v is this board woul do the job.I mean the schematic show a split rqtio of 2.

Works perfectly. I used it to convert 3.3v TTL to 5v TTL to interface a GPS with my D90 camera. For those who are interested: http://www.flickr.com/photos/grink/sets/72157625472950584/with/5230195801/

I tried using one of these to convert from 5V (atmega8) to 3.3V (SD card). The SD card almost replied, but was giving back 7-bit “bytes”. We think the problem was that the 2.5V “high” level wasn’t high enough for the SD cards we tested with. Replacing the RX channels with 3:2 resistor ladders (instead of the 1:1 ladder included on this device) cleared up the problem.

That means the only thing I ended up using from this device was a single TX channel, which would have been easier to do with discrete components.

Hello! Could someone explain what the HV and LV pins are for? I can’t figure out any use other than for probing the input and output voltages for verification purposes. Shouldn’t they simply be pulled to TXI and TXO voltages?
Also, I’m not sure how the mosfets do the voltage step-up. Can someone explain that as well? I would very much appreciate it – I’m fairly new to circuit design. Thanks!

Hi,
I want to convert 5V PWM output of one sensor to 3.3V PWM for interfacing with MSP430 ? Will it work ?
Thank you,
Vatsal

Sparkfun: Nice board. You might want to consider putting a square solder pad on Pin #1 so that someone can tell which pins are #1.

I’ll have to second a few other comments here: the 10k/10k divider on the RX lines had me pulling my hair out for a little while with a touchy SD card (one card worked, even though 2.5V was out of spec, but another card didn’t). Suggestion for a future revision: use FETs for all four lanes. Now, you’ve got a four-port bi-directional level shifter.
Good example (but skip the voltage regulator):
* http://www.rocketnumbernine.com/2009/04/10/5v-33v-bidirectional-level-converter/
* http://www.rocketnumbernine.com/2009/06/13/bidirectional-level-converter-pcb/

The GNDs are common on both sides. Does this mean you can’t have two seperate supplies on each side? Or, can you have 3v side seperate, but just using the 5v gnd? tia

I’ve been experiencing communication issues with this logic-level converter used with 16 bit SPI messages @ frequencies > 2MHz between a 3.3v micro-controller and a 5v chip.
What is the maximum speed achievable with this board?

Is this in the sparkfun eagle library? If so, can’t find it.

Can anyone tell me the dimensions for the row spacing and pin spacing for this device? I would like to attach it to our main circuit board with two rows of pin headers, but need to know the dimensions for the level converter board pin spacings and row spacing. Thanks for help in advance!
Also has anyone confirmed that the latest boards changed the resistors per one of the posts so that it will work for 5v to 3.3 v conversions?

Really great product !
I’ve been using it in quite a few different projects, like here where I needed to interface the 9DOF IMU with a 5V Arduino:
http://trandi.wordpress.com/2011/01/03/razor-9dof-imu-i2c-to-arduino/
Thank you guys for a great product as usually !
dan

I will add to the chorus of people looking for FETs in both directions. I’ve been trying to use this to pair an Arduino with the Sparkfun GM682 eval board. I couldn’t get it to work until I used the TXO/TXI pins to send output signals from the Arduino to the eval board (in other words, HV to LV on TXO/TXI pins, opposite to what is shown in the product photos).
Definitely a great product – just needs improvement!

Hi I Can confirm that using the sparkfun level converter works with the LSM303DLH on a Arduino Uno and stuff
https://picasaweb.google.com/lh/photo/AIiOfELj07YYfxNzte1jWfUyuJg5fbvJpQtmBljJuuk?feat=directlink

Yay for shortcuts!
I wonder if Sparkfun ever thinks about making these a little bigger, with terminal blocks for easy screwing and unscrewing of wires? I know that it sounds silly for logic level voltages, but it would make attaching my sensors (already buried in the ground) to the level shifter a bit easier. Soldering in the field isn’t very much fun…

Well I am wondering how to connect to get 5 volts this for example to a Lithium battery of 3,7v (like this one http://www.sparkfun.com/products/341 ). Because say something like “The board needs to be powered from the two voltages sources (high voltage and low voltage)”, but I think this is the common case where we have a battery and single voltage source. Any suggestions?

Here’s another usage of these really versatile boards:
https://trandi.wordpress.com/2011/09/26/vfd-clock-connects-to-the-internet/
Dan

Using it for I2C

I connected mine the same way this page shows: example

But I still get random crashes. I am using it with the MD25 motor controller and the 9dof sensor stick (SEN-10183). Seems like the Arduino shouldn’t be crashing even if there is junk on the I2C line. It should reject it or give bad data, not crash. I have 1k ohm pull ups on both sides of the converter. Any advice would be appreciated, thanks.

hi can i use this for connecting arduino uno to linksys WRT54GL instead of MAX232??

Can this be used as a 24v to 5V converter?

Hello!

I’d like to connect two arduinos (3.3v and 5v) by the serial connection. Will this logic level converter allow me to transfer data via serial interface?

If not – what is the best solution to link two arduino with different operation voltage?

Thanks.

I was connecting a 3.3V Arduino Pro Mini to a 5V SRF05 Ultra-Sonic Ranger in Mode 2 (single pin for Trigger and Echo.) I could not get it to work for anything using TX_LV and TX_HV (plus HV, LV, and ground connected.) I think the pull-up resistors were the problem. Finally I tried using RX_LV and RX_HV (plus ground), and it worked just fine. I hope this will help someone else.

What are the specs on those resistors? I know they are 10K but what about the rest? I only need one channel and I’m building this myself (first little project). It looks a 0603 SMD resistor. Is it 5% 1/4W?

i want to use a 5v i2c motor driver with my 3.3v controller? how do i have to connect it without getting some kind of loop?

Good Stuff!

If I use this to connect a 3.3V device to a I2C bus, do I still need to insert pull-up resistors? I noticed that it has 10k pull up resistors on each side.

I’m connecting the HV side to my Arduino and as far as I know I’m supposed to connect 1.5k pull ups to 5V, do I need to?

What pull-up resistors would I need on the 3.3V side if any?

See I’m able to receive perfectly, but I can’t request data. The onRequest ISR on the Arduino does not run. I want to know if this could be a problem at the physical layer. Also the 3.3V comes from the Arduino’s regulator and not from the device’s 3.3V regulator. As long as all the grounds are connected together it should be fine right?

Thanks

Why can’t I just use a simple resistive voltage divider with 1.5k + 3k in series, take the output across the 3k resistor to get 3.3v?

That would be used on the TX line of the 5v device. Is it because the +3.3v on the other device’s TX isn’t a strong enough logic high for the +5v device’s RX?