Silencing serial boot messages

[itmarshall]

Hi all,

I am trying to interface my ESP8266 against a pre-existing device over RS-485 (via a TTL-RS485 converter), and wish to suppress the transmission of the boot status messages (the ones at 77400kbps) via the serial Tx line to avoid causing issues for the device.

Looking at the UART documentation, it says that I should call "system_uart_swap". While putting this as the first line in my "user_init" function does suppress any further output (e.g. any "os_printf" invocations), it doesn't stop the boot messages. Likewise, only calling the "system_uart_deswap" function before "os_printf", followed immediately by another "system_uart_swap" does not stop the messages at the next boot.

Is there some other place that I should be invoking "system_uart_swap", or should I change things so that I transmit via UART 1, and receive via UART 0, bypassing the UART 0 transmit functionality?

(I am using SDK version 1.5.2 via the pfalcon "esp-open-sdk" GitHub repository)

Thanks,

Ian

[TriMesh]

As far as I can see, the boot ROM messages will always be output on U0TXD - there is nothing you can do about this, because at the point they are being output your user code hasn't got control of the system. You could try connecting your RS485 TX data line to GPIO2 and then redirecting the output there using the pin multiplexer as one of the first things in your main() routine. You might have to put a weak pullup on the pin to hold the TX line in the mark state until you can reconfigure the pins, though.