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App Inventor 2 经典蓝牙(SPP) 硬件接入：hc05 · App Inventor 2 中文网
...是hc05尤为常见，这里以hc05为例，介绍一下经典蓝牙模块如何接入AppInventor。
HC05 简单介绍
它有六个引脚，引脚的作用如下：
通过厂商App连接串口测试，发现HC-05模块是经典蓝牙2.0，并不支持蓝牙5.0（低功...
Why doesn't os.path.join() work in this case?
...d slashes at the beginning of path components, except when refering to the root directory:
os.path.join('/home/build/test/sandboxes', todaystr, 'new_sandbox')
see also: http://docs.python.org/library/os.path.html#os.path.join
...
Network tools that simulate slow network connection [closed]
...e a public internet service on coffee shop wifi: sudo tc qdisc add dev lo root netem delay 500ms
– Sam Stokes
May 12 '10 at 21:21
7
...
How do I make a Git commit in the past?
... your new commit. If you actually want your new file to be added via a new root commit (no parents), then you need something a bit different:
B---C---o---o---o master
git checkout master
git checkout --orphan new-root
git rm -rf .
git add path/to/file
GIT_AUTHOR_DATE='whenever' git commit
git ch...
What is the difference between a cer, pvk, and pfx file?
... of cryptographic information, including certificates, certificate chains, root authority certificates, and private keys. Its contents can be cryptographically protected (with passwords) to keep private keys private and preserve the integrity of root certificates.
Windows uses .pvk for a private ke...
How to do an INNER JOIN on multiple columns
...ave an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'INNER_JOIN airports to_port ON (to_port.code = flights.tairport) WHERE ' at line 7
– Kiril
Mar 2 '10 at 21:26
...
Postgres and Indexes on Foreign Keys and Primary Keys
..., *, 1 as issue_sort
FROM fk_index_match
WHERE indexid IS NULL
UNION ALL
SELECT 'questionable index' as issue, *, 2
FROM fk_index_match
WHERE indexid IS NOT NULL
AND fkoid NOT IN (
SELECT fkoid
FROM fk_perfect_match)
),
parent_table_stats AS (
...
What is PostgreSQL explain telling me exactly?
MySQL's explain output is pretty straightforward. PostgreSQL's is a little more complicated. I haven't been able to find a good resource that explains it either.
...
Using scp to copy a file to Amazon EC2 instance?
...'t know if you're joking or not... but :/ would try copy the folder to the root of the system, which would give permission errors on all machines without running sudo (or as root).
– Dobz
Jul 29 '14 at 15:17
...
How does one parse XML files? [closed]
... specific element, you can access child elements with the indexer: xmlDoc["Root"], and these can be chained: xmlDoc["Root"]["Folder"]["Item"] to dig down the hierarchy (although it's sensible to validate that these elements actually exist)
– Jason Williams
Mar ...