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
105
106
107
108
109
110
111
112
113
114
115
116
|
<!--
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 2.1.1-1
Then, simply run `make`. This will create
`build/rp2040-*/cmd/sbc_harness/sbc_harness.{elf,bin,hex,uf2}` files:
- The `.elf` is the firmware image plus debugger symbols and
relocation data.
- The `.bin` file is the raw firmware image (`objcopy -Obinary
INFILE.elf OUTFILE.bin`).
- The `.hex` file is the raw firmware image, encoded in the [Intel
HEX](https://archive.org/details/IntelHEXStandard) format (`objcopy
-Oihex INFILE.elf OUTFILE.hex`). Note that unlike the `.bin`, the
`.hex` may contain gaps/holes; holes are filled with 0x00-bytes in
the `.bin`, but tools for working with the `.hex` may fill them
with other data, causing minor differences when comparing the
`.bin` and `.hex`. (Yes, the `.hex` is expected to be about 2.8
times the size of the `.bin`; twice for being ASCII-encoded hex,
plus another 13 bytes overhead for every 16 bytes of input.)
- The `.uf2` file is the `.bin` 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`; each 128-byte block of input is
wrapped in a 256-byte UF2 block.)
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
- 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 if 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)
|
