MTDI confusion on ESP32 Pico D4

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Joined: Tue Dec 10, 2019 1:11 am

MTDI confusion on ESP32 Pico D4

Postby bmbouter » Tue Dec 10, 2019 1:22 am

I've been reviewing the esp32 Pico D4 (v4.1) and I am confused by two aspects of the reference schematic: ... ematic.pdf

1. Correct value of MTDI strapping, pull-up or pull-down?

The schematic shows MTDI connected to VDD33 via R23 which is labeled as 10K(5%)(NC). Based on a statement from page 6 of the esp32 pico data sheet ( ... eet_en.pdf ) it says "the operating voltage of ESP32-PICO-D4’s integrated external SPI flash is 3.3 V. Therefore, the strapping pin MTDI should hold bit ”0” during the module power-on reset."

My question is: Why does the schematic pull up MTDI via R23? According to Table 3 "Strapping Pins" in the esp32 pico data sheet ( ... eet_en.pdf ) it says pulling it up sets it to 1.8V. These statements seem to conflict.

2. Are IO13<->RTS and IO15 CTS connected or not?

The schematic shows them being connected, which makes sense for the data to flow from the CP2102N to the esp32 during flashing, but what does the NC part mean? Also what is the significance of them being green?

Posts: 144
Joined: Thu May 17, 2018 2:26 am

Re: MTDI confusion on ESP32 Pico D4

Postby ESP_Alvin » Tue Dec 10, 2019 1:27 am

Hi bmbouter,

Thanks for the post, we would look into. Thanks.


Posts: 14
Joined: Wed Mar 06, 2019 4:57 pm

Re: MTDI confusion on ESP32 Pico D4

Postby ESP_Peter » Wed Dec 11, 2019 9:01 am

Hi bmbouter,

1. The current ESP32-PICO-D4 integrated a 3.3v SPI flash , so the MTDI/IO12 should be bit "0" ,when the ESP32 boot up.
We reserved the resistor R23 (NC: not connection) pad on the PCB, but The resistor R23 is not mounted on the PCB , it is only reserved for new ESP32-PICO chip with 1.8v SPI flash .
2. Because we use the RTS of CP2102N to control the EN & GPIO0 for auto programming function , so the IO13 and IO15 didn't be connected
to RTS & CTS pin of CP2102N on the board.
3. The green color marked "NC" mean we reserved the pad of component on PCB, but the component didn't be mounted on the PCB. It is not connection .

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