| Electronics > Beginners |
| Several devices on same I2C bus |
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| Yaroooo:
I've a question about level-shifting using mos. In my case I've several my devices that works at 3v3 and communicate between them using I2C bus. I must modify my board to communicate between them, but allowing to connect external boards (not from me) that use 5v as voltage level. Schematic will result like this: I'm sure I'll not have problem to interface 3v3 and 5v. With two 3v3 I'll have something like this: It should work with same principle. Can someone just check and (in case) confirm? |
| magic:
I think it would work, even without 5V pullup on the middle segment, as drawn. Maybe try in in SPICE or on breadboard to be 100% sure. But it's more complex than it needs to be. You can use one 3.3V bus segment for all the on-board devices and add just one level shifter to bridge with the 5V system. |
| Yaroooo:
Thanks for your answer. This 5V devices are already commercial boards with a connector on them, I can't modify them. On other side, create a special adapter will add additional logistic complexity and cost. |
| aries1470:
Hi, Have you looked at the i2c level shifters? They are small and cheap. You can have all the 3p3V ones on one side and the 5V on the other? You can use as many of either one before and after the shifter. I have attached a rather rudimentary drawing on how to do this and a couple of links to ebay for these devices, of which are fairly cheap too. Search for items on eBay - Australia: https://www.ebay.com.au/sch/i.html?_from=R40&_nkw=i2c+5v&_sacat=0&LH_TitleDesc=0&_sop=15 https://www.ebay.com.au/itm/Two-Channel-5V-to-3-3V-TTL-I2C-IIC-Logic-Level-Converter-Bi-Directional-Module/262664199077?hash=item3d28019ba5:g:51sAAOSwZJBX-Ju8 https://www.ebay.com.au/itm/2Pcs-4-Channel-IIC-I2C-Logic-Level-Converter-Bi-Directional-Module-5V-3-3V/301924606812?epid=778328238&hash=item464c1be35c:g:NvIAAOSw5VFWJwmj All the best. |
| JustMeHere:
Look for something just like this: http://www.ti.com/product/PCA9306 Level shifter IC for I2C. http://www.ti.com/product/TXS0102 Bidirectional level shifter that's faster. |
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