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NFC as a programming interface

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I've been working on a watch based around a MSP430, and sharp memory LCDs.

I have spent alot of time developing hardware for this, and not alot of time actually writing code. (If anyone actually read the code for my ledRing project you could probably see that I'm not the most elegant programmer.)


I am on revision 4 of my watch, and I've told myself no more revisions until it is on my wrist telling the time.



But, I'm constantly thinking about ways I could improve the hardware of the watch. one of my ideas was NFC.


I'm wondering if you guys think this is something that would actually be beneficial to a watch?


ST make a few EEPROM/NFC hybrids, basically it's EEPROM, but you can access it via NFC, or via SPI/IIC.




This would allow data transfer to occur between the watch and, say your phone. (setting the time / updating calendar alerts / etc)

Or even my laptop has NFC, I could finish writing new code, place my watch on my laptop and it could be reprogrammed.


This IC also has an interesting property, in that it can output excess RF energy through one of it's pins.

The datasheet doesn't specify how much power, and I'm sure it would depend greatly on the NFC reader, antenna design, and operating distance. I have a board designed with one and an MSP, but I forgot to buy the IC last time I did a digikey order. on my next order I'll get some and I'll be able to do some tests.

But this might enable the watch to run without batteries, or prolong the life of batteries.


Has anyone used these ST micro devices before? I know TI now have their own NFC "dynamic" tags, basically a MSP430 + RF front end.

Anyone done any projects with NFC? I found a few epaper NFC smart stickers online, but they all seem outdated, (~2012)



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Actually I just found this too. An interesting little project. Looks like they have 2 antennas, one just drains power the other used by the RF430CL330 NFC "dynamic tag"


Nice to see more application of NFC over just instant bluetooth pairing (although that is a nice feature)

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I got an NFC bpak from the PotM contest last year I think. I should look into that soon. Meant to study the chip's datasheet but didn't get around to it. One beef I had was the cost of the pre-designed modules; they were more than the whole BPak in small qtys (like $30?)


Sent from my Galaxy Note 10.1

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That was the older DLP one?


I saw that TI have their own boosterpack now, for $20, and then I found this BP from DLP, using the TI NFC IC.



Price of these things has really come down.


Speaking of the POTM, I need to finish off my clock, with the VFD I won. I broke my 5529LP, and the project hasn't moved since :'(

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I've been looking more at NFC after getting myself chipped, and earlier this week I did a day with ST on their low power ARM L0 and NFC.


The dynamic tag stuff is what you need to be looking at - either TI's one that you mentioned or ST's M24LR/M24SR. I have a M24LR discovery board that demos writing to a "tag" and drawing enough power to run a small uC and an LCD display in addition to the EEPROM. I also got a glimpse of their M24SR discovery board that does a little more. Antenna design is apparently reasonably simple for the tags compared to the readers.


I'll try to dig out some more info and links when I'm not trying to post from my phone.


TI are definitely now stocking DLP's 7970A reader booster pack so probably the CL330 one too. TI's free shipping makes a real difference to the price in the UK. I assume it's be the same in Australia.

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Hmm - so how is the security on these devices?

Somebody could download your schedule (or reprogram your watch) with a handshake?


Then again, maybe you could set up your watch to read and reprogram dynamic tags?


In the way I'm thinking of using it, it's not so much of an issue. Using one of these dynamic tags data can be written/read from an EEPROM. The MSP430 could then take that information, store it internally and erase the EEPROM.

NFC, is "near field" to begin with, so even with a handshake, I think the watch would be too far away for effective communication.



If you wanted to be secure, you could implement a form of encryption of the data you are sending as some of the MSP430's include a AES module.  In software you would have to implement some form of public/private key system to negotiate symmetric keys that AES would use.. This might be a bit taxing on a small 16bit device like the MSP430.



To be able to reprogram dynamic tags a more complicated NFC IC would have to be used. :(

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  • 2 months later...

@ greeeg ==> I just joined, sorry for the delay - 

 the MCU is limitation for the AES, not the TRF...luckily the MSP430 handles it well...we have done both perso and AES auth code examples using the MSP430F2370, with the TRF79xA as the NFC/RFID interface, for DESFire EV1 and crypto1 examples for MF Classic. if you are interested in that, just let me know. 



also, i have attached the latest (still work in progress) code example for the value line G2xx LaunchPad + DLP-7970ABP...this code reads tag types 2, 3, 4A, 4B and 5. 

It currently polls for all tag types (# defines can be commented out in main.c at will) then when detecting a tag, it lights up LED on DLP-7970ABP, then reads out UID and indicated by tag memory size data blocks and displays on terminal program. NDEF is handled and displayed for types 4A and 4B, and for type 3 i just have the serial #, PMm and other relevant data coming out. 


it also handles a high density tag from STM which, while it violates the ISO15693 standard, is easy enough to support. 


the intent of this project for me is to have a little fun with work stuff and to spark others to join in/collaborate with me.



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  • 3 months later...

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