QSPI connection on STM32 microcontrollers with other peripherals instead of Flash memories - stm32

Question

I will start a project which needs a QSPI protocol. The component I will use is a 16-bit ADC which supports QSPI with all combinations of clock phase and polarity. Unfortunately, I couldn't find a source on the internet that points to QSPI on STM32, which works with other components rather than Flash memories. Now, my question: Can I use STM32's QSPI protocol to communicate with other devices that support QSPI? Or is it just configured to be used for memories?
The ADC component I want to use is: ADS9224R (16-bit, 3MSPS)
Here is the image of the datasheet that illustrates this device supports the full QSPI protocol.
Many thanks
page 33 of the datasheet

Answer 1

The STM32 QSPI can work in several modes. The Memory Mapped mode is specifically designed for memories. The Indirect mode however can be used for any peripheral. In this mode you can specify the format of the commands that are exchanged: presence of an instruction, of an adress, of data, etc...
See register QUADSPI_CCR.

Answer 2

QUADSPI supports indirect mode, where for each data transaction you manually specify command, number of bytes in address part, number of data bytes, number of lines used for each part of the communication and so on. Don't know whether HAL supports all of that, it would probably be more efficient to work directly with QUADSPI registers - there are simply too many levers and controls you need to set up, and if the library is missing something, things may not work as you want, and QUADSPI is pretty unpleasant to debug. Luckily, after initial setup, you probably won't need to change very much in its settings.
In fact, some time ago, when I was learning QUADSPI, I wrote my own indirect read/write for QUADSPI flash. Purely a demo program for myself. With a bit of tweaking it shouldn't be hard to adapt it. From my personal experience, QUADSPI is a little hard at first, I spent a pair of weeks debugging it with logic analyzer until I got it to work. Or maybe it was due to my general inexperience.
Below you can find one of my functions, which can be used after initial setup of QUADSPI. Other communication functions are around the same length. You only need to set some settings in a few registers. Be careful with the order of your register manipulations - there is no "start communication" flag/bit/command. Communication starts automatically when you set some parameters in specific registers. This is explicitly stated in the reference manual, QUADSPI section, which was the only documentation I used to write my code. There is surprisingly limited information on QUADSPI available on the Internet, even less with registers.
Here is a piece from my basic example code on registers:
void QSPI_readMemoryBytesQuad(uint32_t address, uint32_t length, uint8_t destination[]) {
while (QUADSPI->SR & QUADSPI_SR_BUSY); //Make sure no operation is going on
QUADSPI->FCR = QUADSPI_FCR_CTOF | QUADSPI_FCR_CSMF | QUADSPI_FCR_CTCF | QUADSPI_FCR_CTEF; // clear all flags
QUADSPI->DLR = length - 1U; //Set number of bytes to read
QUADSPI->CR = (QUADSPI->CR & ~(QUADSPI_CR_FTHRES)) | (0x00 << QUADSPI_CR_FTHRES_Pos); //Set FIFO threshold to 1
/*
* Set communication configuration register
* Functional mode: Indirect read
* Data mode: 4 Lines
* Instruction mode: 4 Lines
* Address mode: 4 Lines
* Address size: 24 Bits
* Dummy cycles: 6 Cycles
* Instruction: Quad Output Fast Read
*
* Set 24-bit Address
*
*/
QUADSPI->CCR =
(QSPI_FMODE_INDIRECT_READ << QUADSPI_CCR_FMODE_Pos) |
(QIO_QUAD << QUADSPI_CCR_DMODE_Pos) |
(QIO_QUAD << QUADSPI_CCR_IMODE_Pos) |
(QIO_QUAD << QUADSPI_CCR_ADMODE_Pos) |
(QSPI_ADSIZE_24 << QUADSPI_CCR_ADSIZE_Pos) |
(0x06 << QUADSPI_CCR_DCYC_Pos) |
(MT25QL128ABA1EW9_COMMAND_QUAD_OUTPUT_FAST_READ << QUADSPI_CCR_INSTRUCTION_Pos);
QUADSPI->AR = (0xFFFFFF) & address;
/* ---------- Communication Starts Automatically ----------*/
while (QUADSPI->SR & QUADSPI_SR_BUSY) {
if (QUADSPI->SR & QUADSPI_SR_FTF) {
*destination = *((uint8_t*) &(QUADSPI->DR)); //Read a byte from data register, byte access
destination++;
}
}
QUADSPI->FCR = QUADSPI_FCR_CTOF | QUADSPI_FCR_CSMF | QUADSPI_FCR_CTCF | QUADSPI_FCR_CTEF; //Clear flags
}
It is a little crude, but it may be a good starting point for you, and it's well-tested and definitely works. You can find all my functions here (GitHub). Combine it with reading the QUADSPI section of the reference manual, and you should start to get a grasp of how to make it work.
Your job will be to determine what kind of commands and in what format you need to send to your QSPI slave device. That information is available in the device's datasheet. Make sure you send command and address and every other part on the correct number of QUADSPI lines. For example, sometimes you need to have command on 1 line and data on all 4, all in the same transaction. Make sure you set dummy cycles, if they are required for some operation. Pay special attention at how you read data that you receive via QUADSPI. You can read it in 32-bit words at once (if incoming data is a whole number of 32-bit words). In my case - in the function provided here - I read it by individual bytes, hence such a scary looking *destination = *((uint8_t*) &(QUADSPI->DR));, where I take an address of the data register, cast it to pointer to uint8_t and dereference it. Otherwise, if you read DR just as QUADSPI->DR, your MCU reads 32-bit word for every byte that arrives, and QUADSPI goes crazy and hangs and shows various errors and triggers FIFO threshold flags and stuff. Just be mindful of how you read that register.