ESP32-PICO-D4 integrated 4MB SPI flash connections

[habibh]

Hello Group Members,

ESP32-PICO-D4 module integrates 4-MB SPI flash. I am a little bit confused in the communication between the integraed SPI Flash and ESP32. The integrated flash is of 3.3V so VDD_SDIO(3.3V). The following are the connections of SPI flash in ESP32-PICO-D4:

Pin Number1: /CS = GPIO16
Pin Number2: DO = GPIO17
Pin Number3: /WP = SD_DATA_0/SPIQ(MISO)
Pin Number4: GND = GND
Pin Number5: DI = SD_DATA_1/SPID(MOSI)
Pin Number6: CLK = SD_CLK/SPICLK
Pin Number7: /HOLD = SD_CMD/SPICS0
Pin Number8: VCC = VDD_SDIO(3.3V)

For SPI communication the connections should not be as follows:

Pin Number1: /CS = SD_CMD/SPICS0
Pin Number2: SD_DATA_0/SPIQ(MISO)
Pin Number3: /WP = SD_DATA_3/SPIWP
Pin Number4: GND = GND
Pin Number5: DI = SD_DATA_1/SPID(MOSI)
Pin Number6: CLK = SD_CLK/SPICLK
Pin Number7: /HOLD = SD_DATA_3/SPIWP
Pin Number8: VCC = VDD_SDIO(3.3V)

Can someone explain the connections of integrated SPI Flash in ESP32-PICO-D4.

Regards:
Habib

[WiFive]

Pins can be remapped by efuse so different configurations can work

[habibh]

Dear WiFive,

Thank you for the reply. I have gone through the document and it is written that we can "Any GPIO Pins" for General Purpose SPI. But for EMAC If i want to use EMAC RMII than I cannot use JTAG pins functionality because MTCK is overlapping with EMAC_RX_ER ?

[habibh]

Dear WiFive,

The data sheet of ESP332-PICO-D4 says that "Pins IO16, IO17, CMD, CLK, SD0 and SD1 are used for connecting the embedded flash, and are not recommended for other uses".

If I want to use an external flash with ESP32-PICO-D4 can I use the same pins as of integrated flash of ESP32-PICO-D4 with chip select different as shown in the following attachment ?

Regards:
Habib

[WiFive]

I guess you could if you are going to boot from the external flash, otherwise you would have conflict between flash cache and external flash. But if you are going to boot from external flash why use pico and not just esp32-d0wd.

If you need to use jtag and Ethernet you might be able to skip rx_err signal but this should be for debugging only not production.

[habibh]

Dear WiFive,

I am going to use ESP32-PICO-D4 in my project becuase of space saving as it includes "ESP32 chip, crystal oscillator, flash memory, filter capacitors, and RF matching links". I will be using external flash to increase memory size as embedded flash is of 4MB.

WiFive wrote: I guess you could if you are going to boot from the external flash, otherwise you would have conflict between flash cache and external flash.

In case we are going to boot from internal flash and we are using external flash to increase the memory than in this scenario SPI interface for internal and external with different chip select will not work ?

Thank you for the suggestion of MTCK pin (JTAG) and EMAC_RX_ER (Ethernet) overlapping pin.

Regards:
Habib

[WiFive]

Yes application is executing from flash so it is best to use one large flash chip, in which case you don't save much space with pico 7x7 vs 5x5 and pico costs more.

It is possible to do very compact layout https://fccid.io/XPYNINAW15/Internal-Ph ... os-3854229