4-bit SPI and QSPI

[Andrea Verdecchia]

Maybe my question is trivial but I'm a little confused about the classification and the differences of serial interfaces like 4-bit SPI, QPI, QSPI... In my case I want interface an FTDI to the nRF52840 via SPI and I found the FT220XQ which is a USB Full Speed to 4-Bit SPI and the FT4222HQ which is a USB High Speed to QuadSPI or QSPI. Can the nRF52840 comunicate as 4-Bit SPI using the QSPI peripheral? Are these two interface compatible?

[Kenneth]

Hello,

To get an understanding of the difference between the two you can look a the interface description for both interfaces in the nRF52840 product spec:

SPI: https://infocenter.nordicsemi.com/topic/ps_nrf52840/spim.html#concept_lhv_fx2_wr 

QSPI: https://infocenter.nordicsemi.com/topic/ps_nrf52840/qspi.html#interface_description 

The two interfaces are not compatible no (e.g QSPI can not be used to make SPI or vice versa).

That said, the nRF52840 have very flexible GPIO configuration, so pins that are used as QSPI can be reconfigured to be used as SPI.

Kenneth

[Kenneth]

Reading a bit from the FT220XQ datasheet you linked, I am getting very unsure if QSPI can be used as 4-bit SPI, I would think not since FTDI seem to use the 4-bit SPI naming consistently (and it do differ from the QSPI naming used in for instance FT4222HQ that support QSPI that you also linked). So I expect that it's not compatible, but the best would be to contact FTDI to hear what they say.

Regular SPI can not be used as 4-bit SPI.

Kenneth

[Andrea Verdecchia]

Kenneth said:

I am getting very unsure if QSPI can be used as 4-bit SPI

I have the same doubt but I seen that the nRF52840 DK use the MX25R6435F flash memory interfaced with the QSPI peripheral and in its datasheet is not mentioned the QSPI interface but only a Multi I/O Support: Single I/O, Dual I/O and Quad I/O. This, then, explains my question about the compatibility between QSPI and the Multi I/O, in my case what is called 4-bit SPI. 

Kenneth said:

the best would be to contact FTDI to hear what they say

Yes, I guess.