Problems with MOD-RFID1356MIFARE and ESP32-EVB

[roberto_pi]

Hi,

I'm testing ESP32-EVB with MOD-RFID1356MIFARE in UART mode.
The issue I noticed is that when turning the board on if the RFID card is connected and powered, the ESP32 won't boot until I press reboot button.
While debugging I noticed that the esp32 hangs before reach setup().
When this happens one of the relay led is on.
If I power on the RFID card after boot, everything works fine.

Please help

[LubOlimex]

It is kinda expected when you have two different power supplies and grounds. Probably there is some voltage difference between the grounds that takes some times to settle and connection order affects the state of each board.

Do you need to power the MOD-RFID1356MIFARE from the USB? You can power it from the UEXT via ESP32-EVB. Close jumper 3.3V_UEXT_E (solder its pads together). And while powering from the UEXT don't attach USB cable!

[roberto_pi]

The RFID card is already powered via UEXT connector and the jumper is soldered as requested. the USB cable is not connected. The only way I managed to use the card is dethacing it from the uext connector on the board and activating the UEXT power via a relay in setup()

[LubOlimex]

Maybe it is this same thing:

https://www.olimex.com/forum/index.php?topic=8093.msg30707#msg30707

It was fixed in latest revisions of ESP32-EVB but maybe you got the board a while ago.

What hardware revision is your ESP32-EVB board?

[roberto_pi]

the issue seems to be the one you cited

ESP32-EVB rev. I
RFID1356MIFARE rev. B

[roberto_pi]

and putting a 1k resistor between gnd and gpio04 it seem to work.

[LubOlimex]

It is not pretty solution but it is a solution if it doesn't cause other issues. It requires some further analysis why it happens exactly upon initial power up and it doesn't happen after reset tho.