Cmod A7-35T: Breadboardable Artix-7 FPGA Module

This is a very nice little board. I like it very much. Bear in mind that the SRAM only has a 8 bit bus. Also the pmod connector does have 4 differential pairs, but you can only use 3, since one of the pairs is not in the same group.

This has become my favorite FPGA board by far. I have a RiscV32 in it, plenty of RAM and ROM, and any peripheral I need. I use it for projects and to test devices at work. Fits breadboards for easy wiring.

good price for a powerful tiny FPGA board. Will be nice if the board comes without the PMOD connector.

This is a great little board! I have purchased 2 so far for projects using a riscv32 CPU.

Worked exactly as expected for a project.

I had previously reviewed this product and pointed out that it was not a good module for a beginner but that it was good for an experienced FPGA developer who did not want to have to design an FPGA directly onto a PCB. However, there was a nagging issue with the modules that is no longer true: they now connect flawlessly over USB. They had been picky about cables and took some work to stabilize for programming but they now connect on the first try and are stable.

The schematic available for the part doesn't have all of the parts documented in the manual shown. Pretty sloppy. I expect better from DIgilent. I am really disappointed. --Response from Digilent-- Hello, The programming circuit in the schematic is considered proprietary. For additional information, you can contact us at [email protected]

This my first FPGA, and it is exactly what I wanted. I considered the larger boards with more built-in bells and whistles, but I decided that the breadboard friendly form factor was a better fit for me; on-board peripherals are great, until you want to use those IO pins for something else. Very quick service, even with international delivery. Very happy.

FPGA-wise, the board is highly capable. For many users, the A7-15 or -35 chips will have plenty of fabric. There are 44 digital I/O pins and 2 analog inputs. There's a Pmod on top, too. With the I/O and onboard flash memory, you will be able to store a fairly complex program and drive a significant number of peripherals from it. But the idiosyncrasies and limitations of the board make it a bad place to start if this is your first design. If you are just starting out in FPGA design, I'd recommend the Basys3. It's worth the extra money. One idiosyncrasy is that the USB connection is far more noise-sensitive than other FPGA PCBs by Digilent. There are forum discussions about this with workarounds so check them out before you buy. Another idiosyncrasy has to do with USB bus powering vs. pin powering. If you are ordering this to embed in a PCB, make sure that you can switch between the two different types of power--harder than it sounds given the noise-sensitivity of the USB port--or else do not connect the PCB pins if you intend to always have it bus-connected. This issue is a feature, not a bug, but make sure to read about it in the manual. As far as PCB-mounting the board goes, there is a forum discussion about the socket mount that can be used to socket the board onto a PCB. And because it's an FPGA, the pins drive 3.3V (and read 3.3V) so make sure that you engineer protection and level shifting if you intend to use them with 5V components elsewhere on the PCB. Normal Pmod protection is not on the board itself--you'll need to follow the schematics and read the Pmod specification to do so correctly. Finally, because of the small size of the board there just aren't the switches, indicator lights and buttons that other Digilent PCBs have. There are a few but not enough to really indicate internal operations with any level of complexity. There's no display port (though you can connect one to the Pmod port). So you will need to either prototype your design on another board or become very conversant with on-chip debugging tools such as Xilinx's Integrated Logic Analyzer IP or the simulation tool in Vivado.