[J-core] New Numato Mimas, no serial output from boot loader or Linux

[Rich Felker]

On Fri, Jul 29, 2016 at 04:13:26AM +0000, Brian Bartholomew wrote:
> My Numato Mimas arrived today, and I'm following the recipe at
> http://j-core.org/ to load it with Linux.  Below is a reconstruction
> of what I've tried.  The results I saw matched the tutorial until the
> "Hook up a serial console" step, where I saw no output, no "CPU tests
> passed", nothing, with or without an sdcard inserted.  The switch is
> towards the VGA connector.
> 
> The Dell laptop I'm doing this from is running Ubuntu 14.04.
> 
> $ sudo -i
> root$ service modemmanager stop
> root$ sudo apt-get purge modemmanager
> root$ sudo apt-get install python3 python3-serial
> root$ sudo apt-get install microcom
> 
> $ md5sum mimas_v2.bin vmlinux 
> 390768a7ef9061a19f163061c4e15ac3  mimas_v2.bin
> cebf48571838f9cad0df9e3041ca28b2  vmlinux
> 
> Lines from dmesg:
> 
> [88266.084718] usb 1-1.2: new full-speed USB device number 49 using ehci-pci
> [88266.182025] usb 1-1.2: New USB device found, idVendor=2a19, idProduct=1002
> [88266.182065] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
> [88266.182082] usb 1-1.2: Product: Numato Lab Mimas V2 Spartan6 FPGA Development Board
> [88266.182097] usb 1-1.2: Manufacturer: Numato Systems Pvt. Ltd.
> [88266.183284] cdc_acm 1-1.2:1.0: This device cannot do calls on its own. It is not a modem.
> [88266.183381] cdc_acm 1-1.2:1.0: ttyACM0: USB ACM device
> [88330.709408] usb 1-1.2: USB disconnect, device number 49
> 
> $ sudo python3 MimasV2Config.py /dev/ttyACM0 mimas_v2.bin
> ****************************************
> * Numato Lab Mimas V2 Configuration Tool *
> ****************************************
> Micron M25P16 SPI Flash detected
> Loading file mimas_v2.bin...
> Erasing flash sectors...
> Writing to flash 100% complete...
> Verifying flash contents...
> Flash verification successful...
> Booting FPGA...
> Done.
> 
> Copied vmlinux onto a 32 GB sdcard, I believe it was factory formatted
> with a DOS-type filesystem.
> 
> Now with flash loaded and the sdcard inserted containing vmlinux, I
> see this after powerup:
> 
> 	blue LED on
> 	blue LED off
> 	888 on 7-segment and 3 green LEDs on
> 	green LEDs off
> 	middle 7-segment counts from 0 to 9
> 	--- on 7-segment

If you see that happening, the bootloader is running fine. So the
problem is just in the serial console.

> Meanwhile, no output after the terminal program connects:
> 
> $ stty -F /dev/ttyACM0 -crtscts && microcom -s 115200 /dev/ttyACM0
> connected to /dev/ttyS0
> Escape character: Ctrl-\
> Type the escape character followed by c to get to the menu or q to quit

I have a couple possible guesses at what's happening.

Last time I flashed and tested these boards in some bulk, I hit one
that was doing exactly what you're seeing, and assumed at the time it
was just a defective board. I don't think we ever got around to
diagnosing the problem because we had enough without it. So this might
be your problem.

The other idea that comes to mind is the speed of the (fixed-speed)
interface between the FPGA and the uart-to-usb bridge. The J2
bitstream is set for 19200 bps, to match the board manual (see p.4):

http://community.numato.com/api/productdata/assets/downloads/fpga/mimasv2/MimasV2UserManualV9.pdf

However, there's an upgrade available from Numato to flash the
firmware for the usb-uart to run at 115200 bps, and if I remember
correctly, installing this update also causes the symptoms you're
seeing. It's possible (though I would think unlikely) that new units
are shipping with this update, or that you actually got a
used/refurbished unit or something that had the update applied.

I believe someone has a bitstream build adjusted for the faster serial
port rate that you could install and test to see if this is the issue,
but I don't have a copy myself. I'll ask and see if I can find it for
you or provide instructions to build one if you'd like to build your
own.

You might also check and see it Numato has a test bitstream you could
load that produces serial output and see if that works. I looked
briefly but couldn't find one.

Rich