sdspi VS wbuart32

I have built a lot of open-source C++ tooling for design verification. You can find a lot of my C++ models posted on my Github. Example C++ models include: UART, SPI/DSPI/QSPI Flash, SD-Card (SPI-based interface), VGA Video, Ethernet MDIO, PS/2 mouse, OLED display, SDRAM and more. (I've even simulated PLLs using C++ models ...) I have also written extensively about doing so at ZipCPU.com.

You mean ... sort of like I did in this project? I implemented an SPI based controller, where the controller took care of all the bit-banging for you, but the CPU still needed to issue the commands as appropriate for the protocol?

How about an SD card controller? I know I have a SPI based SD card controller, but the SDIO isn't that much harder. If you look hard enough you can find open source SDIO controllers.

There are also open source versions of many of the pieces you will need. I now use an open source crossbar interconnect for most of my designs. I use AutoFPGA to connect all the pieces together. I mentioned my flash controller above, but I also have a SD Card controller I've used quite successfully. I've also posted a UART to Wishbone bridge and discussed network debugging, both of which I use routinely with the ZipCPU. If for no other reason, these components allow me to load or update software on my CPU even after it's been placed into an FPGA. Of course, many of those components are tied to a Wishbone bus infrastructure. You may find you need a bridge of some type to connect different buses structures together--memory naturally tends to operate at one width and clock, video at another, and your CPU at another, so it helps at times to have a universal bus adapter kit handy.

I have built a lot of open-source C++ tooling for design verification. You can find a lot of my C++ models posted on my Github. Example C++ models include: UART, SPI/DSPI/QSPI Flash, SD-Card (SPI-based interface), VGA Video, Ethernet MDIO, PS/2 mouse, OLED display, SDRAM and more. (I've even simulated PLLs using C++ models ...) I have also written extensively about doing so at ZipCPU.com.

Try this one.

For example, some time after I built my own first serial port transmitter and receiver, someone tried using them in composition: A host (i.e. PC) would transmit a bunch of data, get received by the FPGA, processed by the receiver, and then the data would be sent back to the host via the transmitter. This is a hard test to get right, and my own design failed at the task. (It only returned every other byte!) What I learned from this is that the transmitter must take exactly (10*BAUD_CLOCKS) to transmit a byte. That also means that READY must be high on the last clock cycle of the byte to avoid falling behind. Let's just say that my own serial port wasn't (initially) up to the task. Among other things, the serial port receivers output "VALID" was only one cycle long, and didn't get latched anywhere if the transmitter wasn't ready for it. As I recall, we spent many days scratching our heads at the problem. Eventually, the person using my FPGA switched his host to sending 2-stop bits and things started working. Later, and only a long time later, did I ever find the off-by-one bug in the STOP bit state. My point? Serial port composition is an exacting test, and therefore a good one to work with. You ought to try it.

The core component to the single simulated to TCP port can be found here, in uartsim.cpp. You can find a companion software program that will forward the same TCP port to a hardware serial port here, under the name netuart.cpp.