I am working with the AD9176-FMC Evaluation Board. I am trying to configure the DAC through the SPI interface connected to the FMC connector.
The steps I am following are:
1) Configure the board with the ACE software using the USB cable (this step works ok), to stablish the base configuration.
2) Unplugged the USB cable.
3) Try to perform some SPI writes/reads to check the SPI operation through the SPI connection with the FMC connector.
The ACE software configures correctly the board, but then I want to disconnect the board from the PC and test my SPI VHDL module inside the FPGA performing some single SPI operatinos. I am not sure if what I try to do is possible. Taking a look at the board schematics ("AD9172-FMC-EBZ RevC Schematic.pdf", page 7), it says:
“NOTE: IF USB CABLE IS PLUGGED IN PIC IS THE SOURCE OF SPI BUS AND TXEN SIGNALS. IF USB IS UNPLUGGED FMC INTERFACE IS THE SOURCE OF SPI BUS AND TXEN SIGNAL.”
It also says:
“NOTES: FMC_SPI_EN = LOW, FPGA. FMC_SPI_EN = HIGH, PIC”.
From this information I understand that signal FMC_SPI_EN is send from the FPGA to the mezzanine and controls the source of data to the SPI bus.
The problem is that the ACE software is always the source of data, no matter what the value of FMC_SPI_EN signal is. When I try to send data from the FPGA, data gets out correctly (verified with Xilinx ILA IP Core), but never gets to the SPI signals after the level converter U7 FXL4TD245BQX (CS_N, SCLK, MOSI, MISO). This signals are checked with and oscilloscope. When the source is the ACE, they get the correct value, but when the source is the FPGA, they are ignored.
What is the correct procedure to set the FPGA as the source of SPI data?
Also, what is the purpose of signal PE_CTRL?
Thank you in advance!