ESP32 Forum

I've got a free running GPS on UART1 that if the darn thing gets a fix and starts sending data it corrupts flash downloads as it appears the data gets merges with the real data being sent on UART0 (MD5 match errors etc). Obvious solution is to move the GPS to UART2 or but wondering is there a way to tell the bootloader to not listen to UART1?

Howdy,
The default pins for the UARTs are:

UART0: RX: GPIO3, TX: GPIO1
UART1: RX: GPIO9, TX: GPIO10
UART2: RX: GPIO16, TX: GPIO17

At boot time, UART0 is mapped to the pins above.

For your GPS device, which pins are you using on the ESP32 for RX and TX?

Do remember, that you are not limited to the above pins. You can choose any usable pins for UART1 and UART2 and even redirect UART0s pins.

Hey I first gotta say your book has been a fantastic resource!

GPS is on the default GPIO's 9&10 for UART1. Didn't have a breadboard for the GPS chip so didn't see this until I soldered up a pcb.
Next rev I'll put the GPS on uart2 and for now I'll cut and solder traces unless there is some software majic workaround.

Perry

Your problem in this case is that gpio 9 and 10 are connected to the flash chip. So it is not to do with the bootloader or uart1. Read about the gpio matrix. For most low speed signals there is no reason to use the default pin. Instead you can use the one that is best for PCB layout. But you have to watch the flash pins and strapping pins.

ack! well that's embarrassing..... I just copied my esp8266 pin mapping from last years board and didn't scan the table for new conflicts.

Thanks for the help.
Perry