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ESP32 Optoisolated Programmer – Schematic Description Part 2

Welcome to the second part of our mini-series of blogs about the ESP32 Optoisolated Programmer – Schematic Description. Enjoy!

All our devices share the same programming port. It also allows power to be supplied to the device being programmed. However, there are situations when this capability is undesirable. For this reason, we added a switch to disconnect the 5V and 3V3 power rails.

Also, sometimes it is necessary to disconnect the signals that reset the microcontroller and enable the programming mode. To be able to perform these operations manually, we added buttons J31 and J32.

In addition, the I2C bus signals are also routed out to make it easier to write programs using ICs, mainly sensors, with this interface. Furthermore, the presence of I2C signals in the programming connector makes it possible to program ATECC608 cryptographic processors using the same connector we use for programming the ESP32.

The engineer writing software for the ESP32 can see the status of all the signal lines using the colored LEDs. Transistors T70 and T71 were used so that the LEDs would not overload the EN and Boot signals.

The 3.3V power supply is provided by a popular 1117-3.3 regulator in a SOT223 package. Its performance is sufficient to power the ESP32 together with peripheral circuits.

The diagram also shows all the icons that have been placed on the board – all sorts of legally required marks, fiducials for the assembly machines, and our logo.

In the next section, we will take a closer look at the PCB design and consider how to design an electronic device so that it can be produced as cheaply as possible.

Stay tuned for the next updates about the ESP32 Optoisolated Programmer!

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