ST25DV_Discovery_ANT_C6 is working, but C1 is not.

[NKern.1]

Nordic board + ST25DV_Discovery_ANT_C6 = works great.

Nordic board + ST25DV_Discovery_ANT_C1 = does NOT work (ST25 is not recognized).

Why?

What is the operational difference between C6 and C1?

[Ulysses HERNIOSUS]

Hi NKern.1,

could you detail a bit more on the reader side and its antenna size?

Best Regards, Ulysses

[NKern.1]

C6 has small antenna.

C1 has large antenna.

Connected via I2C to Nordic nRF52-DK.

Connection is identical in both cases, but with C1 Nordic fails to initialize the ST25.

[Ulysses HERNIOSUS]

Hi,

ah, I think I was mistaken - I thought the NFC communication is not working due to antenna size. But you mean with the board with the C1 antenna nRF52-DK cannot access the ST25DV via I2C?!

Ulysses

[NKern.1]

Yes, exactly. ST25-C1 is not detected by NRF board.

We detect connection by writing into and reading from ST25 register 0x53.

[Ulysses HERNIOSUS]

Ok,

clear now! Unfortunately I am not an expert on this board. Other people need to give definite advise then. I assume you already checked the I2C pull-ups?

Regards, Ulysses

[JL. Lebon]

Hello,

On I2C side, the ST25DV_Discovery_ANT_C1 and the ST25DV_Discovery_ANT_C6 are identical. The only differences between the two boards is the size of the antennas.

So in theory, if you can access the C6, you should also be able to access the C1 in the exact same way.

You can check on ST25DV_Discovery_ANT_C1 that R2 and R3 are correctly populated: those are the pull-ups for the I2C signals.

You can also check ST1 jumper: it should connect 1 and 2 for the VCC to be connected to 3v3. If pin 2 and 3 are connected instead, the VCC of St25DV is coming from energy harvesting, which is probably not what you want.

Please also note that on some boards (C1 as well as C6), R1 is wrongly populated. You can remove it for correct GPO behavior. But this should not cause an issue with I2C.

Best regards.

[NKern.1 · Accepted solution]

On another setup it somehow worked properly without modifications.

Appreciate your advises.

[JL. Lebon]

Hello,

What do you mean by "other setup" ? Can you be more precise ?

Did you check the R2 and R3 resistors and ST1 jumper as suggested ?

For reasons I don't know the schematics of those boards is not available on the st.com web site, so I have attached them here for you to be able to check.

Best regards.