flexDF question

I see on the product page that it’s the 8KB version of the EV1. How much usable memory space does the EV1 leave?

I’m asking because I was surprised to see the usable space for a 8KB EV2 is only 7,676 bytes. I don’t have a 8KB EV1 test card, but I have a 4KB EV1, and the usable space is much higher compared to its nominal size - 4,092 bytes I think, I don’t have it here…

This would indicate the EV2 sacrifices some space for extra features the EV1 doesn’t have, and therefore if you don’t need those features and you just want as much space as possible for dumb NDEF storage, you’re better off with an EV1. Correct?

My flexDF also has 7676 bytes of actual usable NDEF usable memory.

I may be wrong here, but I was under the impression that the DESFire EV2 was just the newer version of the EV1. Pretty sure it just has a few newer encryption protocols and whatnot, other than that I thought they were identical.

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Thanks for checking!

Then I guess the real difference is the ratio of actual usable storage space vs nominal space between 4KB and 8KB EV1s then.

Also don’t forget that when you talk about memory space, there is also overhead for pretty much everything you do. The chip might have 8K of raw memory bytes, but when you define an AID like the NDEF container, just creating that container eats up some overhead. Defining keys for that container, even if they are the default keys, eats up more overhead. Finally, companies like this play pretty fast and loose with definitions… It’s much easier to say 8K if it’s “close enough” then to say well it’s almost 8K but it’s really 7600 and whatever bytes. Hey everybody come check out our dandy new NFC almost 8K but not quite but close enough to 8K chip!

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Yeah, that too.

Actually the reported maximum NDEF size for the 4KB EV1 is extremely suspicious - 4.092 is 4 bytes shy of 4,096 bytes, meaning a “true” 4K memory space would contain a 4-byte UID and the NDEF and nothing else?? I don’t think so…

Anyhow, it doesn’t really matter. 7,676 bytes is plenty large enough - too large actually, if you care about transfer time. I was just wondering whose “8 kilobytes” (EV1 or EV2) are worth it for dumb NDEFs. Thanks to Hoker, I now know they’re identical.

Also, and this is purely anecdotal and also probably negligible once the P71 Vivokeys come out, but I have personally found the write/read performance of my flexDF to be hands down the best of all the implants I have, including the P60 Vivokey I’ve got. With payloads of similar size, I feel like I get noticeably better read/write times with my DESFire. From what I’ve heard, the P71 is a big step up in terms of speed, but until then, I think the DF line is probably the fastest. Again, purely anecdotal.

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Also purely anecdotal here, but my flexDF2 has amazing read range compared to the HF side of the NExT in my same hand.

Depending on the smartphone i’ve used it reads up to 1cm/0.3 inches away so I expect even better with a building/commercial reader.

I tweaked your statement for you :arrow_up:
Because of the 2 types of antennas