ESP32 TX pin not sending data

[brent.yiu]

I have a custom design using the ESP32-D0WD-V3 SoC and i'm having trouble connecting to the device over UART. I am using the ESP32-Prog programmer to try and flash the target device.

Using an oscilloscope with probes on CHIP_PU, TX, RX, and GPIO0, I can see that the data being sent over the RX line to the ESP32-D0WD-V3 is the correct packet for Synchronization. The problem is that nothing comes back on the TX line from the ESP32 to the ESP32-Prog programmer.

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[ESP_Sprite]

Are you sure the ESP32 is in download mode? Is the ESP32 happy in general? (You can check that by seeing if it spits out a boot message over UART0 whenever you power it on)

[brent.yiu]

I figured out that the reason the ESP32 wasn't sending data is because an external crystal is required. Once I added an external crystal to my design, I was able to communicate with the ESP32.