ESP8266 Community Forum

- Mon Sep 22, 2014 12:03 pm #826 10mils came from the molex appnote on the antenna. Still a mismatch on the SMA connector.... I know ...

A Transistor on GPIO0 would be an option. I still see a use for GPIO0 , even when it has to be at a defined level at boot up. Such GPIO/bootstrap behaviour is quite common on SoCs. E.g. it still could be used as (Soft)I2C SDA for example.

- Mon Sep 22, 2014 2:08 pm #839

10mils came from the molex appnote on the antenna. Still a mismatch on the SMA connector.... I know ...

The antenna is probably designed for a 4-layer 1mm thick PCB, for which trace width is much smaller, thus the 10 mils.

A Transistor on GPIO0 would be an option. I still see a use for GPIO0 , even when it has to be at a defined level at boot up. Such GPIO/bootstrap behaviour is quite common on SoCs. E.g. it still could be used as (Soft)I2C SDA for example.

Actually, it all depends on the default level at bootup: in this case, GPIO0 is high for normal Flash boot, and low for UART download, so you can have a pull-up on GPIO0 and use it for a signal that defaults to high level, like I2C SDA as you suggested. However, I2C requires some rather low values for these pull-up resistors (typically 1k), which may raise the board idle power significantly when I2C is not required.

- Mon Sep 22, 2014 3:13 pm #843 Yep probably 4l , would make sense for the width.
Wondering how that will turn out and how it measures in the end

GPIO0 is pull'ed up with 12k at the moment (on the paper) . I still can change that in the BOM.

Power is no problem on the devboard. First it is a devboard Second the ESP8266 sits on it's own VCC island, separated from the rest of the circuitry (ftdi,flash,pull ups) by a jumper for more accurate current measurement of the ESP8266 itself.

I thought about the RTS / Boot thing a bit more, isn't there a upload to ram and run command in the bootloader? Do we need to switch GPIO0 then at runtime wit RTS?

- Mon Sep 22, 2014 3:19 pm #844

I thought about the RTS / Boot thing a bit more, isn't there a upload to ram and run command in the bootloader? Do we need to switch GPIO0 then at runtime wit RTS?

Not that I know of... There is an over the air provisioning using the dual Flash "partitions", but the bootloader requires to change the GPIO0 level at boot time. Of course, you can still move a jumper, but as it is a dev board, you will probably do it very often, so a software-controlled solution would be nice.