1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
|
<!--
README.md - Description of sbc-harness
Copyright (C) 2024-2025 Luke T. Shumaker <lukeshu@lukeshu.com>
SPDX-License-Identifier: AGPL-3.0-or-later
-->
# Building
Building requires CMake, GNU Make, an "arm-none-eabi" toolchain
(including newlib), and picotool (including the `.cmake` files;
e.g. `/usr/lib/cmake/picotool/*.cmake`).
At the time of this writing, on Parabola GNU/Linux-libre that means:
- make 4.4.1-2
- cmake 3.30.3-1
- arm-none-eabi-binutils 2.42-1
- arm-none-eabi-gcc 14.1.0-1
- arm-none-eabi-newlib 4.4.0.20231231-1
- picotool 2.0.0-2
Then, simply run `make`. This will create
`build/rp2040-*/cmd/sbc_harness/sbc_harness.{bin,uf2,elf}` files. The
`.bin` file is the raw firmware image; the `.uf2` file is that wrapped
into a [USB Flashing Format (UF2)](https://github.com/microsoft/uf2)
container that can be used with the bootrom flasher (yes, the
`.uf2` is expected to be about twice the size of the `.bin`); the
`.elf` is the firmware image plus debugger symbols.
There are several ways of putting this firmware file onto the harness:
1. bootrom flasher: Hold the "BOOTSEL" button when powering on. The
harness will appear to a host PC as a USB storage device. Simply
mount the device and copy the `.uf2` file to the device. It will
automatically reboot into the new firmware image.
2. debug port: Using OpenOCD (see `HACKING.md`), run the OpenOCD command
`program /path/to/sbc_harness.elf reset`.
If OpenOCD is not already running:
```
openocd -f interface/cmsis-dap.cfg -f target/rp2040.cfg -c "program $PWD/build/rp2040-Debug/cmd/sbc_harness/sbc_harness.elf reset exit"`
```
If OpenOCD is already running:
```
socat STDIO TCP:localhost:4444 <<<"program $PWD/build/rp2040-Debug/cmd/sbc_harness/sbc_harness.elf reset"
```
3. Use `flashprog` or `flashrom` and a SOIC-8 clip to directly
program the flash chip. I'm not sure why you would do this
instead of one of the above.
# Usage
The harness uses DHCP to acquire an IPv4 address, then serves the 9P
protocol over TCP:
- TCP port: 564 (9P does not have a standard TCP port number, but
this is the default port number used by most 9P-over-TCP clients,
including the Linux kernel's v9fs driver).
- Supported protocol versions:
- `9P2000` (base protocol): Yes
- `9P2000.u` (Unix extension): Yes, with Linux kernel
architecture-"generic" errnos. This will match the Linux kernel
errnos on most architectures (but, as of Linux v6.7, not on
Alpha, MIPS, PA-RISC, PowerPC, or SPARC; I am unsure whether on
these platforms the kernel's v9fs filesystem driver will map the
"generic" errnos to the architecture-specific errnos for you).
- `9P2000.L` (Linux extension): No, it's an abomination and
unlikely to ever be supported
- `9P2000.e` (Erlang extension): No, but if you want it and ask
nicely I'd be happy to add it (I'm not sure why you'd want it
though).
- Authentication: None
There are lots of 9P clients that you can use. 9P is a filesystem
protocol; and you can mount it directly with the the Linux kernel's
v9fs filesystem driver, with plan9port's `9pfuse`; or interact with it
without mounting it using the shell commands `9p` (from plan9port),
`wmiir`, or `ixpc`; or interact with it without mounting it by using a
library for your programming language of choice.
Some notes on choosing a client:
- On x86-32, the Linux kernel v9fs driver is known to drop entries
from directory listings; I advise using 9pfuse instead of you want
to mount it on 32-bit systems.
- I generally like mounting it as a real filesystem, but this means
that you only get errno errors, and the more-helpful error strings
are discarded.
- The sbc-harness only supports 7 concurrent connections to the 9P
server, so while shell commands are handy for poking around, for
real use where you're doing things in parallel you'll likely want
to mount it or use a library that can reuse existing connections.
# Bugs/Limitations
- Only supports 7 concurrent TCP connectsions to the 9P server (due
to limitations in the W5500 TCP-offload chip; TODO: investigate
using a software TCP/IP stack with the W5500 in MAC-raw mode)
- Only supports 2 concurrent 9P requests per connection (I wanted a
static limit, and 2 seemed reasonable)
- Only supports IPv4, not IPv6 (due to limitations in the W5500
TCP-offload chip; TODO: investigate upgrading to the W6100 or using
a software TCP/IP stack with the W5500 in MAC-raw mode)
|
