I’ve been working with those modules from a while.
Not very expensive, i’ve paid 1$ for a piece. And it is not exactly genuine IC on it, no markings at all
So I’ve been thinking about using that module with other interface than default SPI.
After searching the documentation I know chow to change the interface.
Depending on signals on pins 32 - EA, and 1 - I2C it is possible to set the module in desired mode.
For those 1$ modules the most easy conversion is from standard SPI to UART, because you only need to cut out one trace that we have easy acces.
That is the only trace that goes to the pin 32, it is tricky because that trace goes from left and is covered by white paint so hard to see at the first look.
Si in 2 seconds we have got UART, and still can use SPI if we fix back our cutting.
If we want I2C what would be better in many cases, than we need to desolder the MRFC522 IC, because I2C enable line is grounded (set LOW) under the chip, and we need to reflow the IC after cutting.
It is not so hard, and i’m doing it with hot air with my GAS hot air gun/soldering iron from DREMEL.
There is no temperature controll so just needs to check not to burn the IC by overheating.
Just posting here for people who needs save 3 pins , because UART or I2C takes less than SPI.
And conversion to uart is so simple…
Post your code here, because we have got library for SPI, and there is not much for UART or I2C, i’ll post the code for I2C because i have got some when i finish testing.
Have a good fun.
below photos of how to change the connections.