XIAO nRF52840 NFC Antenna Insights

andriandreo · June 6, 2024, 7:22am

The NFC function will perform well when we use the “Seeed nRF52 mbed-enabled Boards Library”.

I managed to replicate the Arduino example code in the Wiki using the “Seeed nRF52 mbed-enabled Boards Library” as stated and both antennas below:

Both worked right just after soldering without further circuit tuning. Later, I added two 43 pF tuning caps from each NFC pad to GND to further enhance the interrogation distance for the TAOGLAS FXR.07.A.DG.

The ~40 pF cap value was calculated from subsection “6.14.10 NFCT antenna recommendations” in nRF52840 MCU product specification datasheet.

PJ_Glasso · June 6, 2024, 1:21pm

Hi there,
Excellent Job on this, I’m certain there isn’t any good info on the topic like this post.
Thank you for the R & D.
it Should really help and demonstrate this NFC area of Xiao.
GL PJ

elliottlambert · March 12, 2025, 2:44pm

Hi andriandreo,

I have pretty much copied your setup. I am using the a slightly different molex (1462360001). I have then flashed the Seeed Studio nrf52840 with the following code:

#include <NFCT.h>

void setup() {
// set the NFC message as first parameter and the language code as second
NFC.setTXTmessage(“Hello World!”, “en”);
// start the NFC module
NFC.start();
}

void loop() {
}

(I am also using the Seeed nRF52 mbed-enabled Boards Library)

I then used the taginfo app for IOS to try and scan the antenna, but nothing. Are there any other tips you could give me. Am I missing anything?

Also could you give me an estimate of the interregation range of the molex antenna you are using. Is is a couple of cm’s?

Thanks,
Elliott

PJ_Glasso · March 12, 2025, 3:03pm

Hi there,

So, You get it’s only a TAG, GREAT! SO the Mobile phone you are using is it BLE5.0 compatible. Most Older Iphones are NOT. So there’s that.
Have you tried or used the NFC_tools APP ? Allows to program a real tag and read them as well. A good way to test function. Works well with a matched antenna.

HTH
GL PJ

this is the DEV board antenna…

elliottlambert · March 12, 2025, 3:39pm

The phone I am using is iPhone 10 so yes is BLE5.0 compatible (although not sure why this is relevant as I am testing NFC), and yes I have also tried the NFC_tools App. Neither apps are able to detect the TAF. :(( Have you got it working. Did you flash the same code I did?

PJ_Glasso · March 12, 2025, 3:57pm

Hi there,

Ok Great , You made it past step one.
Have you used the tools to make a TAG or read a TAG? (tone suggest YES) so next step the…
Which BSP are you using to compile it with?

Can you post a picture of your actual device, DUT ?

Yes , the code is similar to the WiKi for it also.

Can you post the first 3 lines of the compiler output ? and the last ten lines before it uploads?

HTH
GL PJ

It isn’t Rocket Science but there is some nuance to it.

elliottlambert · March 12, 2025, 4:12pm

I am using tools to simply read the tag, hoping that it will read hello world. I cannot post any images (i think because i am new user) but it is pretty much identical to the molex/seeed nrf image posted by adriandreo above. Short equal length wires soldered to both the antenna and the nfc terminals. I am using Arduino IDE to compile and flash, here is the output. WARNING: library NFC claims to run on nrf52 architecture(s) and may be incompatible with your current board which runs on mbed architecture(s).
Sketch uses 87536 bytes (10%) of program storage space. Maximum is 811008 bytes.
Global variables use 44384 bytes (18%) of dynamic memory, leaving 193184 bytes for local variables. Maximum is 237568 bytes.
Upgrading target on /dev/cu.usbmodem14301 with DFU package /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch_mar11a.ino.zip. Flow control is disabled, Single bank, Touch disabled
########################################
########################################
########################################
########################################
###########
Activating new firmware
Device programmed.

PJ_Glasso · March 12, 2025, 4:42pm

Hi there,

Well that’s close… Yea it’s a spam thing after a couple reply’s it let’s you post more stuff’s.

it’s The first three lines Starting with “FQBN: …”
to get started you can use the code tags also for a box. “</>” paste it in there.

for example…

FQBN: esp32:esp32:XIAO_ESP32C3
Using board 'XIAO_ESP32C3' from platform in folder: C:\Users\Dude\AppData\Local\Arduino15\packages\esp32\hardware\esp32\3.0.7
Using core 'esp32' from platform in folder: C:\Users\Dude\AppData\Local\Arduino15\packages\esp32\hardware\esp32\3.0.7

or more like this .

FQBN: Seeeduino:nrf52:xiaonRF52840Sense
Using board 'xiaonRF52840Sense' from platform in folder: C:\Users\Dude\AppData\Local\Arduino15\packages\Seeeduino\hardware\nrf52\1.1.9
Using core 'nRF5' from platform in folder: C:\Users\Dude\AppData\Local\Arduino15\packages\Seeeduino\hardware\nrf52\1.1.9

Go again,

HTH
GL PJ

You’re close , You’ll get it.

elliottlambert · March 12, 2025, 5:17pm

loading library from /Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/libraries/Spi_Flash: invalid library: no header files found
FQBN: Seeeduino:mbed:xiaonRF52840
Using board ‘xiaonRF52840’ from platform in folder: /Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3
Using core ‘arduino’ from platform in folder: /Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3

Detecting libraries used…
/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-g++ -c -w -g3 -nostdlib @/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/defines.txt @/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/cxxflags.txt -DARDUINO_ARCH_NRF52840 -mcpu=cortex-m4 -mfloat-abi=softfp -mfpu=fpv4-sp-d16 -w -x c++ -E -CC -DARDUINO=10607 -DARDUINO_SEEED_XIAO_NRF52840 -DARDUINO_ARCH_MBED -DARDUINO_ARCH_MBED -DARDUINO_LIBRARY_DISCOVERY_PHASE=1 -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840 -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/api/deprecated -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/api/deprecated-avr-comp -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/nfc/t2t_lib -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/nfc/t2t_lib/hal_t2t -iprefix/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino @/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/includes.txt /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch/sketch_mar11a.ino.cpp -o /dev/null
Alternatives for NFCT.h: [[email protected]]
ResolveLibrary(NFCT.h)
→ candidates: [[email protected]]
/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-g++ -c -w -g3 -nostdlib @/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/defines.txt @/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/cxxflags.txt -DARDUINO_ARCH_NRF52840 -mcpu=cortex-m4 -mfloat-abi=softfp -mfpu=fpv4-sp-d16 -w -x c++ -E -CC -DARDUINO=10607 -DARDUINO_SEEED_XIAO_NRF52840 -DARDUINO_ARCH_MBED -DARDUINO_ARCH_MBED -DARDUINO_LIBRARY_DISCOVERY_PHASE=1 -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840 -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/libraries/NFC/src -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/api/deprecated -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/api/deprecated-avr-comp -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/nfc/t2t_lib -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/nfc/t2t_lib/hal_t2t -iprefix/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino @/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/includes.txt /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch/sketch_mar11a.ino.cpp -o /dev/null
Using cached library dependencies for file: /Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/libraries/NFC/src/NFCT.cpp
WARNING: library NFC claims to run on nrf52 architecture(s) and may be incompatible with your current board which runs on mbed architecture(s).
Generating function prototypes…
/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-g++ -c -w -g3 -nostdlib @/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/defines.txt @/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/cxxflags.txt -DARDUINO_ARCH_NRF52840 -mcpu=cortex-m4 -mfloat-abi=softfp -mfpu=fpv4-sp-d16 -w -x c++ -E -CC -DARDUINO=10607 -DARDUINO_SEEED_XIAO_NRF52840 -DARDUINO_ARCH_MBED -DARDUINO_ARCH_MBED -DARDUINO_LIBRARY_DISCOVERY_PHASE=1 -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840 -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/libraries/NFC/src -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/api/deprecated -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/api/deprecated-avr-comp -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/nfc/t2t_lib -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/nfc/t2t_lib/hal_t2t -iprefix/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino @/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/includes.txt /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch/sketch_mar11a.ino.cpp -o /private/var/folders/gb/0rq8th213_n7m3dm7qgh4fx40000gn/T/2717861616/sketch_merged.cpp
/Users/elliottlambertparsons/Library/Arduino15/packages/builtin/tools/ctags/5.8-arduino11/ctags -u --language-force=c++ -f - --c+±kinds=svpf --fields=KSTtzns --line-directives /private/var/folders/gb/0rq8th213_n7m3dm7qgh4fx40000gn/T/2717861616/sketch_merged.cpp
Compiling sketch…
/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-g++ -c -w -g3 -nostdlib @/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/defines.txt @/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/cxxflags.txt -DARDUINO_ARCH_NRF52840 -MMD -mcpu=cortex-m4 -mfloat-abi=softfp -mfpu=fpv4-sp-d16 -DARDUINO=10607 -DARDUINO_SEEED_XIAO_NRF52840 -DARDUINO_ARCH_MBED -DARDUINO_ARCH_MBED -DARDUINO_LIBRARY_DISCOVERY_PHASE=0 -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840 -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/libraries/NFC/src -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/api/deprecated -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/api/deprecated-avr-comp -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/nfc/t2t_lib -I/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/nfc/t2t_lib/hal_t2t -iprefix/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino @/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/includes.txt /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch/sketch_mar11a.ino.cpp -o /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch/sketch_mar11a.ino.cpp.o
Compiling libraries…
Compiling library “NFC”
Using previously compiled file: /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/libraries/NFC/NFCT.cpp.o
Compiling core…
Using previously compiled file: /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/core/variant.cpp.o
Using precompiled core: /Users/elliottlambertparsons/Library/Caches/arduino/cores/Seeeduino_mbed_xiaonRF52840_d0a97f57c02b70ce731c209c462debe3/core.a
Linking everything together…
/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-g++ -E -P -x c /Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/linker_script.ld -o /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/linker_script.ld
/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-g++ -L/Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8 -Wl,–gc-sections -w -Wl,–as-needed @/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/ldflags.txt -T/Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/linker_script.ld -Wl,-Map,/Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch_mar11a.ino.map --specs=nosys.specs -o /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch_mar11a.ino.elf /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch/sketch_mar11a.ino.cpp.o /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/libraries/NFC/NFCT.cpp.o /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/core/variant.cpp.o -Wl,–whole-archive /Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/cores/arduino/mbed/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_SDK_15_0/components/nfc/t2t_lib/nfc_t2t_lib_gcc.a /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/…/…/cores/Seeeduino_mbed_xiaonRF52840_d0a97f57c02b70ce731c209c462debe3/core.a /Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/libs/libmbed.a /Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/libs/libcc_310_core.a /Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/libs/libcc_310_ext.a /Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/variants/SEEED_XIAO_NRF52840/libs/libcc_310_trng.a -Wl,–no-whole-archive -Wl,–start-group -lstdc++ -lsupc++ -lm -lc -lgcc -lnosys -Wl,–end-group
/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-objcopy -O binary /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch_mar11a.ino.elf /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch_mar11a.ino.bin
/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-objcopy -O ihex -R .eeprom /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch_mar11a.ino.elf /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch_mar11a.ino.hex
/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/tools/adafruit-nrfutil/macos/adafruit-nrfutil dfu genpkg --dev-type 0x0052 --application /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch_mar11a.ino.hex /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch_mar11a.ino.zip
Zip created at /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch_mar11a.ino.zip

Using library NFC at version 1.0 in folder: /Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/libraries/NFC
/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/tools/arm-none-eabi-gcc/7-2017q4/bin/arm-none-eabi-size -A /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch_mar11a.ino.elf
Sketch uses 87536 bytes (10%) of program storage space. Maximum is 811008 bytes.
Global variables use 44384 bytes (18%) of dynamic memory, leaving 193184 bytes for local variables. Maximum is 237568 bytes.
Performing 1200-bps touch reset on serial port /dev/cu.usbmodem141101
Waiting for upload port…
No upload port found, using /dev/cu.usbmodem141101 as fallback
“/Users/elliottlambertparsons/Library/Arduino15/packages/Seeeduino/hardware/mbed/2.9.3/tools/adafruit-nrfutil/macos/adafruit-nrfutil” --verbose dfu serial -pkg “/Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch_mar11a.ino.zip” -p /dev/cu.usbmodem141101 -b 115200 --singlebank
Upgrading target on /dev/cu.usbmodem141101 with DFU package /Users/elliottlambertparsons/Library/Caches/arduino/sketches/52386E8CE59F93C3083B72C146E7A7F8/sketch_mar11a.ino.zip. Flow control is disabled, Single bank, Touch disabled
Opened serial port /dev/cu.usbmodem141101
Starting DFU upgrade of type 4, SoftDevice size: 0, bootloader size: 0, application size: 87544
Sending DFU start packet
Sending DFU init packet
Sending firmware file
########################################
########################################
########################################
########################################
###########
Activating new firmware
Device programmed.

DFU upgrade took 5.889823913574219s

PJ_Glasso · March 13, 2025, 2:39am

Hi there,

Ok so that’s the full monty , but I see you are using the 2.9.3 BSP
The wiki was a 2.9.2 so I would first start by rolling that back and try again. I recommend try just the non embed too, 1.1.3 BSP.
or /then
Post up a picture so we can check it over.
and the Whole code you are using or just the wiki?
NOTE:
WHAT is the Inductance of the -0001 version ?
If it’s not exact then IT won’t work.
If you used 43pf tunning caps, and a different Molex Ant. IT won’t work.

If you look at the OP data sheets for both antennas for example they list the Micro-Henries of the respective devices at the resonant frequency of 13.56Mhz
I couldn’t find the spec on yours. -0001

you use it in the equazion and add the appropriate tuning values,

HTH
GL PJ

elliottlambert · March 13, 2025, 12:11pm

New day, lets see if we can crack this.
Ok, I have downgraded the BSP to 2.9.2 from 2.9.3. The a non-mbed BSP wont work because the nfc library is part of that BSP. I have also bought the same molex andriandreo was using, to make it EXACTLY the same. So I’m now using the MOLEX 1462360051 with 1.4uH inductance. I am not tuning, as andriandreo was able to make it work without tuning with this antenna. STILL WONT LET ME UPLOAD IMAGE!! (although i promise is exactly the same as adrian image)

Code-wise, I am flashing the exact code from the wiki, using arduino IDE. Here is the code:

#include <NFCT.h>

void setup() {
// set the NFC message as first parameter and the language code as second
NFC.setTXTmessage(“Hello World!”, “en”);
// start the NFC module
NFC.start();
}

void loop() {
}

I am then using two nfc reading apps on two phones to see if I can read the hello world from the tag.

Still no luck!!!

Elliott
p.s. thanks for all your help

PJ_Glasso · March 13, 2025, 3:21pm

HI there,

OK , So you are checking off the right boxes…

That low WILL require Tuning Caps, His unit was 2uH so not apples to apples yet!.
On my Sammy 8+ it has to be naked, in a case it won’t read. On a 9+ it works straight away… Same with a Real TAG!.

Your close , You’ll get it.

Keep going
GL PJ

elliottlambert · March 13, 2025, 3:36pm

I checked the datasheet linked in his description. It also has an inductance of 1.4uH, although I take your point the tuning will help. Do you think an antenna that small will even be able to be detected by a phone (its only 15mm/15mm). I will have another go with capacitors and get back to you. Are you sure theres nothing else I need to do on the software side. I’ve seen bits and pieces about making sure the pins are enabled for nfc, and not configured as standard gpio pins.

Thanks again

PJ_Glasso · March 13, 2025, 3:57pm

Hi there,

So , even the wire length’s has to be the same, I suspect the OP was off a tad (13.56MHz) for the smaller one and that was why he thought using a larger antenna(then HAD to use the CAPs) to get it working. HAd he tuned the small one with some caps it would have worked better IMO.
YMMV.
For a 1.4 µH antenna, the required total capacitance to resonate at 13.56 MHz is:

Total capacitance: 98.4 pF
Each capacitor: 49.2 pF (one from NFC1 to GND, one from NFC2 to GND)

Recommended Capacitor Values

Use ~49 pF capacitors (C0G/NP0 type) for stability.
Ensure your PCB layout doesn’t introduce excessive stray capacitance.
try that and be sure your using the correct side as well, the adhesive side is aluminum and doesn’t pick up well or at all from the BACK!

HTH
GL PJ

When it’s working I get a good 3 inch operation on the dev kit
You don’t have to use SMD caps either , Seeed should offer:
A) a standard antenna PAD with caps on it, one could just solder on.
B) a Larger NFC selection of hardware.
C) give me free stuff forever Ok maybe not the last one.

I see an opportunity for a small pcb with everything on it for long and Short range.

elliottlambert · March 13, 2025, 4:48pm

How did you get to your answer 2 x 49.2pF capacitors? Are you assuming 0 for Cp and Cint? I got 98.4 pF per capacitor, 196.8 pF total. I’m thinking one of us has dropped a 1/2 somewhere. Are you using the equations from the nrf52480 data sheet? Sorry to be a pain just want to be right before I order them!! Other than that, thanks for everything. I’ll try again with the capacitors and let you know how it goes! One last thing, when you say you got 3 inches range, which antenna is that with??

PJ_Glasso · March 13, 2025, 4:57pm

Hi there,

Yes, It’s divided in Half to get the actual Values.
I use the DeV Board with the Factory ant in previous picture.

HTH
GL PJ

fyi:
Nordic specifies that two capacitors (one per NFC pad) should each be half of the total capacitance.

Thus, for 2.6 µH, each capacitor should be:

Ceach=Ctotal2=20.32=10.15 pFC_{\text{each}} = \frac{C_{\text{total}}}{2} = \frac{20.3}{2} = 10.15 \text{ pF}Ceach=2Ctotal=220.3=10.15 pF

elliottlambert · March 13, 2025, 5:01pm

Great setup!

Nordic specifies this in the datasheet:
An antenna inductance of Lant = 2 μH will give tuning capacitors in the range of 130 pF on each pin. The total capacitance on NFC1 and NFC2 must be matched.

if its 130pF per capacitor for 2uH, surely it will be higher for 1.4uH as inductance is in the denominator?

elliottlambert · March 14, 2025, 2:44pm

Finally I can upload an image!!

Here is the board with two 180pF capacitors for tuning. Still not working tho. Im sure its something to do with the config side or software. will it ever work??

andriandreo · April 15, 2025, 10:51am

Sorry for not answering you back earlier. I am quite busy at the moment working on my PhD thesis xd

A few remarks (from my own experience):

I checked your code and build log a few weeks back and everything seemed OK.
With these small molex antennas I found that they work even without tuning caps.
(And most important in your case as I remember) I struggled QUITE A LOT reading the tags with iPhone devices (in fact, I don’t recall being able to reaching them at all, some weird internal settings IDK).

If you have the chance, try reading it with any NFC-enabled Arduino smartphone as my own is able to read them easily just while unlocked without even opening any NFC-reading app whatsoever.

Hope I helped!

PJ_Glasso · April 15, 2025, 2:16pm

Hi there,

I too notice some Iphones don’t seem to like the BLE 5.0
older iphones definitely.

HTH
GL PJ