Unable to get esp32_passthrough working

[InternetUnexplorer]

Note
This is outdated, see below comments!

Hi there, I'm having trouble programming the ESP32 on my ULX3S v3.0.8 v3.1.7 85k (came with ESP32-WROVER-E pre-attached).

I've tried esp32_passthru from here, as well as the bitstreams in ulx3s-bin/passthru/passthru-v20-85f, ulx3s-bin/dfu/85f-v20, and ulx3s-bin/dfu/85f-v317. I've programmed each to flash and disconnected/reconnected the ULX3S to make sure, but the ESP32 won't enter download mode; it keeps running the program (currently MicroPython) without interruption.

I think I've narrowed it down to not being able to reset the ESP32; as I understand it driving wifi_en low should disable it completely:

module ulx3s_passthru_wifi(
    output wire ftdi_rxd,
    input  wire ftdi_txd,
    output wire wifi_rxd,
    input  wire wifi_txd,
    inout  wire wifi_en
);
    assign ftdi_rxd = wifi_txd;
    assign wifi_rxd = ftdi_txd;
    assign wifi_en = 1'b0;
endmodule

However, with this minimal example the ESP32 is still enabled and I can access it via serial; wifi_en seems to have no effect! And if the ESP32 can't be reset, I don't see how one can enter download mode, which is probably why passthru isn't working?

I'm able to get it into download mode by using jumper J3, but this is kind of impractical since it takes a few tries to get it working and I'd like to program the ESP32 a lot as I'm testing things out.

[InternetUnexplorer]

So, it turns out my board is actually a v3.1.7 (even though fujprog says it's a v3.0.8), thanks to @goran-mahovlic for pointing that out. I'm able to program using ulx3s-bin/dfu/85f-v317 now, although it fails some of the time (which is probably why I didn't realize it worked when I tested it). I'm still confused by the wifi_en behavior though, does it work differently on v3.1.7?

[InternetUnexplorer]

Okay, it turned out I forgot to copy the v316 constraints file to my little example above; enabling/disabling the ESP32 with wifi_en seems to work now. Sorry for the confusion and many thanks again to Goran for helping me with this!

Flashing is still very unreliable though (about 50/50), and I'm not sure what I'm doing wrong (I'm going to try to get another cable today to see if that improves things). Do you have any advice for how to improve it/where to find more information about how the flashing process works?

[InternetUnexplorer]

Ok, one more update (sorry), now that I have the new constraints file I was able to get everything working reliably with just following:

assign ftdi_rxd = wifi_txd;
assign wifi_rxd = ftdi_txd;
assign wifi_en = ftdi_nrts;
assign wifi_gpio0 = ftdi_ndtr;

Now esptool.py is able to enter download mode on the first try every time, and everything seems to work! I don't have the ESP32 connected to anything else yet, but this is all I need for now so I'll close this issue :)

I'm still not sure what all of the extra stuff esp32_passthru is doing means, but I can figure that out later. I'm guessing it's probably at least somewhat related to programming the FPGA from the ESP32?

[emard]

Great you got it working! passthru is usb-serial bridge from US1 to ESP32 thru FPGA. additionally passthru contains US2 DFU bootloader so FPGA can self program its FLASH, it is much faster than fujprog so it improves multiplatform compatiblity. It should be reliable too, if not exact 100% but much better than 50% success rate. To program over US2 you can use some DFU programmer or openFPGALoader but not fujprog and some DIP SW set or BTN held at power on to autostart user code instead of bootloader. To support features of big ESP32-WROVER like its 2MB RAM and WIFI-RMII-ETH bridge, part of ESP32 wiring had to change from 3.0.x to 3.1.7 boards

…

On 11/21/22, InternetUnexplorer ***@***.***> wrote: Ok, one more update (sorry), now that I have the new constraints file I was able to get everything working reliably with just following: ```verilog assign ftdi_rxd = wifi_txd; assign wifi_rxd = ftdi_txd; assign wifi_en = ftdi_nrts; assign wifi_gpio0 = ftdi_ndtr; ``` Now `esptool.py` is able to enter download mode on the first try every time, and everything seems to work! I don't have the ESP32 connected to anything else yet, but this is all I need for now so I'll close this issue :) I'm still not sure what all of the extra stuff esp32_passthru is doing means, but I can figure that out later. I'm guessing it's probably at least somewhat related to programming the FPGA from the ESP32? -- Reply to this email directly or view it on GitHub: #4 (comment) You are receiving this because you are subscribed to this thread. Message ID: ***@***.***>

[InternetUnexplorer]

Thanks a bunch for the explanation! Programming the FPGA with DFU definitely seems nice (fujprog is a bit slow), so I might study the passthru code further in the future if I have time to experiment with that.