[seL4] Re: Implementation of SeL4

10 Jun 2022

      Hi Sriram,
This might be relevant to your experience. I recently tried running
sel4test on my intel based desktop and ran into similar issues. My desktop
has a serial(db9) connector on the back panel. The experience was the same
when connecting directly to the serial port on the motherboard for a
different desktop that did not have a db9 on the back panel.

I tried doing the same experiment Peter suggested - i.e., try from Linux to
check if the serial port worked fine. But I was still getting garbled data,
I played with baud, parity, stop bits, etc., but no luck. The serial to USB
cables I tried was:

   - USB to TTL Serial Cable - Debug / Console Cable for Raspberry Pi from
   Adafruit https://www.adafruit.com/product/954: This is often sold with
   raspberry pies.
   - USB 2.0 to TTL Level
   https://www.aliexpress.com/item/33001930568.html?spm=a2g0o.productlist.0.0.47dd5428RdUDOc&algo_pvid=8c8abdcc-160b-4eab-9a2d-ae8d0ff7f9c8&algo_exp_id=8c8abdcc-160b-4eab-9a2d-ae8d0ff7f9c8-6&pdp_ext_f=%7B%22sku_id%22%3A%2212000027174900820%22%7D&pdp_npi=2%40dis%21CAD%21%212.68%21%21%21%21%21%402101e9cf16540569516133604e7863%2112000027174900820%21sea:
   This one let me change the logic's voltage level to either 5V or 3.3V. I
   thought that the desktops logic level may be 5V instead of the typical 3.3
   for raspberry pi.

Neither of these cables worked. But the following cable worked with pretty
much the default baud of 115200, parity options.

   - https://www.amazon.ca/gp/product/B075YHFMC7

I do not plan to dig into why I got garbled data with the first two cables
and correct data with the last cable - as I already spent way too much time
on this :) Here is my write-up
https://github.com/sid-agrawal/sel4-gpi-manifest/blob/main/x86_64-desktop.md
with some serial setup details, it is pretty much a copy of the original
write-up https://docs.sel4.systems/Hardware/IA32, with some more details
on the serial config.

Hope this helps.
Sid

On Wed, Jun 8, 2022 at 4:17 PM Peter Chubb  wrote:
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"Sriram" == Sriram via Devel  writes:
Sriram> We are facing certain issues as follows:
Sriram> - Booting via flashdrive, Output on Screen shows "Loading sel4
Sriram> OK","Loading rootserver OK" and no other output in display, we
Sriram> recieved junk values using serial port Output.
You do not say what payload you are booting.  I strongly suggest
getting seL4test running on your system before trying to run a VM.
'junk values' on the serial output implies your serial terminal is
misconnected or not at the right baud rate.
If you boot your system into Linux, then do
  stty 115200 < /dev/ttyS0
  yes > /dev/ttyS0
as root, you will get output on the serial terminal you can use to
debug this.
Peter C
--
Dr Peter Chubb                https://trustworthy.systems/
Trustworthy Systems Group                        CSE, UNSW
Core hours: Mon 8am-3pm; Wed: 8am-5pm; Fri 8am-12pm.
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[seL4] Re: Implementation of SeL4

Sid Agrawal