SPI FLASH in ARTY Boards?

[yathAg]

Hey @BrunoLevy, firstly thanks a lot for this wonderful tutorial, and I absolutely love your work!!

I have successfully completed up to step 21 of episode 1 on the arty35T board, and now the SPI flash is driving me crazy. I have been using the F4PGA toolchain and openFPGALoader for programming.

These are the things that I have taken care of and please lemme know if I'm missing out on anything:

1. Modified the Verilog code to match SPI_FLASH_READ from spi_flash.v
2. modified ADDR_OFFSET in ST_NICCC.C to 4096*1024 as the arty requires around 1.4MB in flash
3. Made sure to have the correct pins enabled in the constraints file

## Quad SPI Flash
set_property -dict { PACKAGE_PIN L13   IOSTANDARD LVCMOS33 } [get_ports { SPIFLASH_CS_N }]; #IO_L6P_T0_FCS_B_14 Sch=qspi_cs
set_property -dict { PACKAGE_PIN K17   IOSTANDARD LVCMOS33 } [get_ports { SPIFLASH_MOSI }]; #IO_L1P_T0_D00_MOSI_14 Sch=qspi_dq[0]
set_property -dict { PACKAGE_PIN K18   IOSTANDARD LVCMOS33 } [get_ports { SPIFLASH_MISO }]; #IO_L1N_T0_D01_DIN_14 Sch=qspi_dq[1]
set_property -dict { PACKAGE_PIN L16   IOSTANDARD LVCMOS33 } [get_ports { SPIFLASH_CLK }]; 

to upload to the flash I'm using openFPGALoader -b arty_a7_35t -o 4194304 -f scene1.dat

I believe this should cover everything...but well I get no output on the screen. any idea what I could do? Thanks for all the help!

[BrunoLevy]

Hi,

I think you have done what I'd have done, that is interface the slowest version (SPI_FLASH_READ from MappedSPIFlash.v) and only then go for the faster versions.

One thing that would explain (just in case, you have probably seen that already): your clock needs to be 50 MHz or lower (for faster clock, you need to use SPI_FLASH_FAST_READ).

What I would do:

• find the reference of the SPI flash on the ARTY
• take a look at the data sheet
• write a simple program that reads the first bytes of the FLASH and that displays it to the standard output. It will correspond to the FPGA bitstream, so it should contain something. If you display it in hex and ascii, you will probably see at the beginning something like XC7, at least there will be something. If you see something, there are good chances the SPI driver works (else it shows 0000)
• if the SPI driver works, then it is a problem with ADDR_OFFSET. Make sure the SPI flash has sufficent space, the SPI driver has sufficently wide address lanes to address all the SPI flash (I guess it is larger on the ARTY than on the other boards I have supported up to now, this may explain).

[yathAg]

Thanks for the input,

So mem_wordaddr for SPI is only 20 bits wide, so with a total address width of 22 bits, the maximum addressable space is 4194303 or 4 MB, as mentioned in the tutorial.

The configuration of the arty takes 2192012 bytes, and hence I decided to store the data in the arty starting at 4194304.

• I modified the mem_wordaddr to be 22 bits wide

• changed the base address in io.h, putchar.s and start.s, to 0x1000000

• modified spi_flash.v and step22.v to the same specs

I have attached an image of the output I get and any idea what the issue could be.

[BrunoLevy]

Great so you got something, it means the SPI Flash hw is probably working,

• First thing to do is to make sure of the total capacity of the SPI Flash, did you find this information ?
• Second thing: instead of changing the memory mapping (putchar.S etc...), you may add a fixed offset in HW, in SPI Flash (at the moment you load the shifter with addr, you can load it with addr + offset
• Third: rather than testing with ST_NICCC, store a text file in SPI Flash, then write a program that displays the stored characters, will be easier to see what's going on.