Alternative chip for ST25R3911B?

[DIvan.1]

Hello,

Till now I was using ST25R3911B NFC chip for read/write (ISO15693).

Unfortunately ship have long lead time.

Can you please advice me which chip to use as alternative to have less changes on the PCB as possible?? (ST25R3912, ST25R3915, ST25R3917,... ??)

Thank you,

Domen

[Ulysses HERNIOSUS]

Hi Domen,

 

the ST25R3911B, ST25R3914, ST25R915 are mostly the same (pinout and register interface). You can check them out (features and availability).

 

ST25R3916, 17, 18, 20 are a different family (changed pinout, different features, changed register interface). When using RFAL they can be used in the same way.

 

Best Regards, Ulysses

[DIvan.1]

Thank you for your advice, I think ST25R3915 would be the best.

In my situation, I have a big closet where have 30 precisely positioned items. On the back side of each item I will put NFC chip + antenna and microcontroller.

I noticed that ST25R3918 have also I2C communication... Is it possible to use only NFC chip without moicrocontroller and connected them via I2C to the master microcontroller?

All the best,

Domen

[Ulysses HERNIOSUS]

Hi Domen,

of course you can connect the ST25R3916/8 to any microcontroller using I2C. For your example there are a few caveats:

1. ST25R3916/8 comes only with one I2C address so your master controller will need 30 I2C busses
2. Signal integrity on such long I2C lines
3. RFAL supports only one chip instance, so you would need to switch on a layer below RFAL the used I2C bus/ST25R3916 and on a layer above RFAL ensure proper initalization/deinitialization to keep everything in a consistent state when switching.
4. Depending on the used features you may put additional real-time burden on the master mcu. This is the case when using ST25R3911B(family) as the FIFO is only 96 bytes and also the case when using card emulation on ST25R3918 (which I presume you won't use).

Best Regards, Ulysses

[DIvan.1]

Thank you for caveats. I think It's not worth it. It will be better to use NFC chips and microcontrollers and then microcontrollers connect via I2C with master controller.

What do you think about the idea to have more antennas at one NFC chip? (if this is these even acceptable)

All the best,

Domen

[Ulysses HERNIOSUS]

Hi Domen,

Both 3911 and 3916 devices can support two single-ended antennas: AN5592.

For more you would need to use external multiplexers. We don't have a lot experience with this.

Best Regards, Ulysses

[DIvan.1]

Hello,

Can you please explain how to detect more than one Tag?

I'm using ST25R3911 and rfal library.

Best,

Domen

[Ulysses HERNIOSUS]

Hi Domen,

please have a look at how-do-i-read-multiple-nfc-tags-with-library-stswst25r016. All the information there holds also for ST25R3911B.

Regards, Ulysses

[DIvan.1]

Hello,

Can you suggest me or provide some document with electrical scheme of ST25R3915.

I need to develop standalone PCB.

Best regards,

Domen

[Ulysses HERNIOSUS]

Hi Domen,

ST25R3911B and ST25R3915 are pin-to-pin and software compatible (except for AAT). So you can just look at all the available information for ST25R3911B.

Basic electrical schemes can be found in 1.2 Application information of the datasheet.

Best Regards, Ulysses

[DIvan.1]

Perfect. The TRIM1 and TRIM2 (red mark in the picture below) line should just delete in antenna matching scheme or not?