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Update Readme #264

Merged
merged 1 commit into from
Mar 6, 2018
Merged

Update Readme #264

merged 1 commit into from
Mar 6, 2018

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samuelsadok
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The hi-level of the 3.3V output of the RPi is sometimes sufficient to be recognized as high by the LEDs. I changed the readme slightly to reflect this. (source: I have one of my SK6812 strips connected directly)

@Gadgetoid
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The logic high of most LEDs parts is VCC * 0.7. When powered at 5V that means logic HIGH is defined as 3.6V (up to 5.5V according to: https://cdn-shop.adafruit.com/datasheets/WS2812B.pdf) and 3.3V is technically in the undefined band between LOW and HIGH.

But my experience matches yours; I've driven several different styles of WS2812-compatible LED directly from 3.3V while powered at 5V and they appear to work fine.

I would probably change the text slightly to:

WS281X LEDs are typically powered at 5V and require at least a 3.6V signal to recognise a logic HIGH.
Depending on your actual LED model and data line length you might be able to successfully drive your LEDs with 3.3V logic.
However for any serious application you should use a level shifter to convert from the Raspberry Pi's 3.3V GPIO/PWM to 5V.

@jgarff jgarff merged commit 48cec21 into jgarff:master Mar 6, 2018
brindosch pushed a commit to hyperion-project/rpi_ws281x that referenced this pull request Apr 5, 2018
* Added delay to ensure reset time being met with low led counts (jgarff#157)

* Fix includes as per jgarff#178 (jgarff#189)

* clean up doco and strandtest (jgarff#187)

* updated documentation on GPIO usage
strandtest now defaults to GRB colour order
added version.h to gitignore

* updated python readme

* more README cleanup

* added notes on spi max transfer size

* Fix freeze after running for long time  (jgarff#197)

* Whitespace cleanup

* Move channel_protocol_time so it handles 32 bit Color LEDs.

* Fix a freezing issue when running for a long time.

When current_timestamp overflowed 2^64, rolling back to 0 and ws2811->render_wait_until had not, this caused an incredibly long usleep in ws2811_render.

* Update README.md (jgarff#191)

* Update README.md

* updated spi buffer size location

* Add -lrt link flag for systems with older glibc (jgarff#195)

* Fix 32-bit overflow in get_microsecond_timestamp(). (jgarff#206)

On Raspbian systems, the tv_sec member of struct timespec is 32 bits
wide.  get_microsecond_timestamp() was overflowing in 32-bit
arithmetic on this member.  This causes the time that it returns to
jump ahead by many thousands of years at uptime = 35 minutes, 48
seconds.  (While the starting point for CLOCK_MONOTONIC_RAW is
unspecified, it seems to track system uptime in practice.)

This overflow didn't cause noticeable problems for me--ws2811_render()
skips the sleep when it thinks such a huge amount time has
elapsed--but it could possibly result in rarely-occurring skipped
frames if the WS2811 reset time isn't effectively honored by
ws2811_render().

* Add TOOLCHAIN option for cross compilation (jgarff#213)

Use this option if you want to cross-compile the library.
Typical usage is:

  scons TOOLCHAIN=arm-linux-gnueabihf

* Add -Wextra compile option and adapt code to suppress warnings (jgarff#214)

The changes in code are mostly type casts between int ann unsigned.

* Add shared library rasbpian package builder.  The package is not built by
default.  To generate the package you need:

- The dpkg-deb utility.
- Use "scons deb" to generate the package.

* Merge user-settable gamma correction into master (jgarff#216)

Merge user-settable gamma correction into master

* Bug fixes for Stretch and Compute Module support (jgarff#222)

* Bug fixes

Missing aligned(4) attribute in pcm.h makes the PCM case failing under
Stretch, due to a newer version of gcc (6.x).
Also fixed a bug in check_hwver_and_gpionum, so original Model A is
recognised.

* README, using SPI on RPi3

Added note to change the core frequency to 250 MHz when using SPI on
RPi 3.

* README fix

* Add support for Compute Module 1 and 3

* Fix undefined clock_gettime symbol

* add missing memory allocation for SPI mode (jgarff#231)

* added Ctrl-C handler to turn off all LEDs on exit (jgarff#140)

* added Ctrl-C handler to turn off all LEDs on exit

* added option -c

* Fix for segmentation fault on exit for Python API (jgarff#239)

Remove useless __del__ because the cleanup() function gets called by
atexit().
Remove ws.ws2811_fini() call which causes the SEGFAULT on exit.
Python does not complain about the memory leak in this way.

* Add support for new A+ hardware.

* Change default DMA channel to safe choice (10) (jgarff#253)

add warning on README.md

* Add getBrightness for brightness feedback from the buffer (jgarff#248)

* Instructions to install the Python library (jgarff#254)

Solving issue jgarff#142

* Fix for non-root users & SPI (jgarff#257)

* Fix for non-root users can use SPI

* use DEFINE'd device strings

also add a note to the readme

* Basic Golang Examples (jgarff#256)

* Added golang example

* Added basic README for golang examples. Added os exits for errors during color wipes for golang examples

* Fix the default DMA in python code (jgarff#266)

DMA 5 causes file system errors on PI 3

* Fixed typo in README.md (jgarff#273)

Was perusing recent commits and saw this.

* clarify electrical notes (jgarff#264)

* Fixed strandtest.py (jgarff#258)

* Fixed keyboardinterrupt, indentation inconsistency, & a few other minor bugs.  Added shebang.

* Fixed KeyboardInterrupt.  Again.

* KeyboardInterrupt works now.  For sure.

* Tabs to spaces, removed redundant signal handling

* Removed unused sys module import

* Added Raspberry Pi 3 B+ (jgarff#276)

* Added Pi 3 B+

* Remove unused import
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3 participants