Error programming

[Rudy94]

Hi everyone,
I am contacting you for information regarding a problem we are having when programming and communicating with the ESP8684. Attached is a connection diagram. The firmware from VScode to the ESP appears to be uploaded. However, the communication between the AM625 and the ESP only shows garbled characters and no initial communication.

[Sprite]

Hard to say without seeing the code running on either platform. Garbled data usually means a baudrate (or rarely, other serial parameters) mismatch, have you checked this?

[Rudy94]

Hi Sprite,
Please verify the following:
1- am6251 transmits at 115200. With the oscilloscope I have good data and speed.
2- When resetting and putting the ESP8684 into download mode, it responds with garbage characters and the speed is approximately 1/13 µs.
3- I programmed it using VSCode with an example code echoing to uart0 at a speed of 115200. I put the esp8684 in download mode, flashed it from VSCode without problems, put it in bootloader mode and the garbage code it prints on the screen is much larger and it does nothing.

I read on some forum that the EN tennis should be at a pull-up, I changed it today and nothing changed.

[Sprite]

EN should indeed be high for the chip to work; you normally want to put a power-on reset RC network on there. See the hardware guidelines for that chip for an example. It's odd that you get garbage even with only a pulldown installed; I'd expect that to keep the ESP in reset and as such silent.

The ESP8684 can run off two crystals, 26 or 40MHz. Given that you see 'garbage' on the UART on bootup, it's likely your module has a 26MHz crystal in it (it's actually bootup chatter at 74880 baud). Could be that you still have a 40MHz crystal selected in your project configuration (Menuconfig), can you check that?

[Rudy94]

I changed the frequency in the menuconfig to 26MHz and now I have readable output from the VS Code console. However, communication between the ESP8684 and AM625 is not possible. The ESP8684 is always sending garbage data.What can I do?

[Sprite]

Again, might be a baud rate error. Have you tried scoping out the serial signal, see what time the shortest pulses on the line take? 1s/that is your baud rate.