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USB Serial Mod

A project I’m working on with the ESP8266 requires a USB module. The one I bought from Sparkfun has a USB C port, and 6 pin-outs.

original module face original module back

Unfortunately, to be able to wire up the ESP for flashing, the ESP needs access to the RTS pin, which is not made available by this usb/serial breakout. However, the chip itself does have that pin.

With some inspiration from others, and some confirmation of the concept, I decided to add an extra terminal soldered to the correct pin on the chip. I tested by holding the jumper manually, and it worked great.

manually holding jumper to pin

However, the RTS pin is not the only thing I need. This USB module has the ability to operate at either 3.3V or 5V. But while the ESP operates at 3.3V, I need 5V to charge a battery (3.3V will not do this without a voltage amplifier). Fortunately, I can steal the 5V needed from the pad normally intended to switch the module to 5V mode.

With that, I cut and stripped some jumper wires with female terminals, and soldered them in place.

soldered module face soldered module back

After a test of flashing the ESP with this module and confirming it behaves as expected, I wrapped it up by protecting the new soldered connections with hot-melt glue. I also glued the terminals to the edge of the original serial port, to expand the interface from 6 to 8 pins.

complete module face complete module back

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