Is it possible to configure the QSPI as slave to receive data from an external ADC

[Simon86]

Hello,

I'am trying to connect the AD7771 (https://www.analog.com/media/en/technical-documentation/data-sheets/AD7771.pdf) with a STM32F413. The question is, if it is possible to configure the QSPI as slave to receive the data from the AD7771 via DOUT0-DOUT3. In this case, the AD7771 is the master and provides the CLK. How can I configure the QSPI that the CLK Pin of the µC is an input and uses the CLK of the AD7771?

FYI: I have already connected the DOUTs to the normal SPIs and it works fine. The problem is that their are not enough SPIs to connect the other "modules" and so I want to save the normal SPIs which are connected to the AD7771.

Thanks for your support.

[S.Ma]

No(t yet?) ==> add to STM32 Wish list ?

If you are not using all SPI at the same time, you can use alternate pins for the SPI to implement a bus MUX. (MODER/AF GPIO bit fields).

Same for I2C or master serial interfaces

[Simon86]

Ok. Thanks for your quick answer. Good idea to implement a bus mux. I will try it.

[Andreas Bolsch]

The QSPI is strictly master-only as it's intended for external memory, and transfer modes are restricted when compared to the normal SPI interfaces, e. g. byte oriented.

[Jaroslav BECKA]

Another solution might be using SAI (Serial Audio Interface) or PSSI (Parallel Slave Synchronous Interface), if available on your product.

Alternatively, you could use GPIO, DMA and TIM. Please take a look into AN4666: Parallel synchronous transmission using GPIO and DMA.

There is an associated software package X-CUBE-PARAL-COM.

https://www.st.com/en/embedded-software/x-cube-paral-com.html

https://ez.analog.com/data_converters/precision_adcs/w/documents/2855/interfacing-the-ad7768-ad7768-4-to-a-microcontroller

[JR2963]

Hi, I have similar problem with reading data from AD7771 via DOUTx line (I want to read all 8 channels on 1 line DOUT_0)). 1 channel has 4 bytes (1 for header an 3 for ADC data)

I want to use SAI interface. I tried to read data like that, but there are some weird data HAL_SAI_Receive(&hsai_BlockB3,(uint8_t *) GlSAI_DMA_Buff, 8, 0xffffff);

What I am not sure about is:

• hsai_BlockB3.SlotInit.SlotActive - What does it mean? I want to have 8 channels on DOUT_1 line - so there is 32 slots? Or all this "pack" is taken as 1 slot?
• hsai_BlockB3.Init.DataSize  - for me it should be 32? (1 channel sends 4 bytes)
• hsai_BlockB3.FrameInit.FrameLength = 256; - it sounds good for me when I want to read 8 channels (1 channel have 1 B header and 3 B for ADC data) 4x8x8 = 256 bits
• what bout that? hsai_BlockB3.FrameInit.ActiveFrameLengt
• what bout that? hsai_BlockB3.SlotInit.SlotNumber

All my settings is here:

hsai_BlockB3.Instance = SAI3_Block_B;

hsai_BlockB3.Init.Protocol = SAI_FREE_PROTOCOL;

hsai_BlockB3.Init.AudioMode = SAI_MODESLAVE_RX;

hsai_BlockB3.Init.DataSize = SAI_DATASIZE_8;

hsai_BlockB3.Init.FirstBit = SAI_FIRSTBIT_MSB;

hsai_BlockB3.Init.ClockStrobing = SAI_CLOCKSTROBING_FALLINGEDGE;

hsai_BlockB3.Init.Synchro = SAI_ASYNCHRONOUS;

hsai_BlockB3.Init.OutputDrive = SAI_OUTPUTDRIVE_DISABLE;

hsai_BlockB3.Init.FIFOThreshold = SAI_FIFOTHRESHOLD_EMPTY;

hsai_BlockB3.Init.SynchroExt = SAI_SYNCEXT_DISABLE;

hsai_BlockB3.Init.MonoStereoMode = SAI_STEREOMODE;

hsai_BlockB3.Init.CompandingMode = SAI_NOCOMPANDING;

hsai_BlockB3.Init.TriState = SAI_OUTPUT_NOTRELEASED;

hsai_BlockB3.Init.PdmInit.Activation = DISABLE;

hsai_BlockB3.Init.PdmInit.MicPairsNbr = 1;

hsai_BlockB3.Init.PdmInit.ClockEnable = SAI_PDM_CLOCK1_ENABLE;

hsai_BlockB3.FrameInit.FrameLength = 256;

hsai_BlockB3.FrameInit.ActiveFrameLength = 1;

hsai_BlockB3.FrameInit.FSDefinition = SAI_FS_STARTFRAME;

hsai_BlockB3.FrameInit.FSPolarity = SAI_FS_ACTIVE_LOW;

hsai_BlockB3.FrameInit.FSOffset = SAI_FS_FIRSTBIT;

hsai_BlockB3.SlotInit.FirstBitOffset = 0;

hsai_BlockB3.SlotInit.SlotSize = SAI_SLOTSIZE_32B;

hsai_BlockB3.SlotInit.SlotNumber = 1;

hsai_BlockB3.SlotInit.SlotActive = 0x00000000;

Thank you for any advice, Jan.

[Jansunil]

Hi @Community member​ 

Here are the answers to your questions:

hsai_BlockB3.SlotInit.SlotActive - What does it mean? I want to have 8 channels on DOUT_1 line - so there is 32 slots? Or all this "pack" is taken as 1 slot?

Slot active would be the number of slots that you intend to read, irrespective of what the DOUT_1 actually sends out.

(1 << slots_per_frame) - 1 would be the value here.

hsai_BlockB3.Init.DataSize - for me it should be 32? (1 channel sends 4 bytes)

Yes, the data size represents the data size of one slot, which in your case would be 32.

hsai_BlockB3.FrameInit.FrameLength = 256; - it sounds good for me when I want to read 8 channels (1 channel have 1 B header and 3 B for ADC data) 4x8x8 = 256 bits

The frame length value needs to be calculated as follows:

(data_size +data_offset) slots_per_frame;

In this case, it would be (32+0)*(8) = 256 .

what bout that? hsai_BlockB3.FrameInit.ActiveFrameLengt

Active frame length does not hold any significance in case of operation in slave mode.

what bout that? hsai_BlockB3.SlotInit.SlotNumber

Slot number would be the number of slots per frame. In this case it would be 8 (8 channels) 

Thanks,

Janani Sunil