WS2801 and Beaglebone

[jocelyn....@gmail.com]

Hello guys !

I'm looking for a way to use a strip of 50 WS2801 leds with my beaglebone black. All the documents I've found are related to Arduino or Raspberry so I have some issues to know the path I should follow. 

I have this driver : http://elinux.org/BeaconBoard so currently I'm trying to rebuild an Angstrom kernel with this. 

If anyone has already done it or have any advice I'm eager to hear it ! 

Thanks !

[William Hermans]

http://forum.beaglefu.com/topic/80-beaglebone-black-drive-a-ws2811-led-strip-with-spi/#entry217

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[jocelyn....@gmail.com]

Thanks !! I'll try to adapt this to ws2801.

[William Hermans]

They should use the same communication "protocol" right ? Just SPI, but yeah I have no hands on there, but I've known the person who made that post for a while, so the information presented will be good.

[jocelyn....@gmail.com]

I guess ! Maybe the timing is different, I'll have to check the spreadsheet for that

[jocelyn....@gmail.com]

I've just managed to make it work so I will give some feedback for those who would like to do the same.

• Start with a fresh Angstrom kernel.
• Disable HDMI :
• Plug in the mini-usb cable from your board to your computer, open the Beaglebone partition and the uEnv.txt inside it.
• Add this to the file : capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN
• Boot the board. Run : cat /sys/devices/bone_capemgr.*/slots. You should see the two lines concerning the HDMI with P-O-- flags. There's no L in this so it means it is disabled.
  
• Follow the instructions to enable SPI : http://hipstercircuits.com/enable-spi-with-device-tree-on-beaglebone-black-copy-paste/ . You don't need to try the bus yet, just make sure to download the python libraries he mentioned.
  
• You have rebooted your board, if you run  cat /sys/devices/bone_capemgr.*/slots you should see a line with BB-SPI1-01.
• Download this to your BB : https://github.com/doceme/py-spidev
  
• Run python setup.py install
• In this repository : https://github.com/hackerspaceshop/RaspberryPI_WS2801_Bridge/tree/master/software. Download the LedStrip_WS2801.py file to your BB. You can use the demo.py to have an idea of what you can do with the library.
• HW time : make sure your led strand is correctly powered (http://learn.adafruit.com/adalight-diy-ambient-tv-lighting/wiring-1 if you need help). Wire the led strand input to your BB : GND goes to pin 1 of P9, CO to pin 31 of P9, DO to pin 30 of P9.
• Finally run python demo.py

Enjoy ! If it helped you, just let me know ; )

[Mark A. Yoder]

Thanks for the detailed instructions.  It's working for me with very little effort.  In fact, if your are running the latest Debian image [1] the setup is even easier. py-spidev is already installed and you don't have to disable the HDMI, rather you just disable a PWM.

• beagle$ cat /sys/devices/bone_capemgr.*/slots

0: 54:PF---
1: 55:PF---
2: 56:PF---
3: 57:PF---
4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G
5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI
7: ff:P-O-L Override Board Name,00A0,Override Manuf,bspm_P9_42_27
8: ff:P-O-L Override Board Name,00A0,Override Manuf,bspm_P9_41_27
9: ff:P-O-L Override Board Name,00A0,Override Manuf,am33xx_pwm
10: ff:P-O-L Override Board Name,00A0,Override Manuf,bspwm_P9_21_b

• Slot 10 is the PWM, so disable it with:  beagle$ echo -10 > /sys/devices/bone_capemgr.*/slots
• beagle$ cat /sys/devices/bone_capemgr.*/slots

 0: 54:PF--- 

 1: 55:PF--- 

 2: 56:PF--- 

 3: 57:PF--- 

 4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G

 5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI

 7: ff:P-O-L Override Board Name,00A0,Override Manuf,bspm_P9_42_27

 8: ff:P-O-L Override Board Name,00A0,Override Manuf,bspm_P9_41_27

 9: ff:P-O-L Override Board Name,00A0,Override Manuf,am33xx_pwm

• It's gone, next enable SPI 0, beagle$ echo BB-SPIDEV0 > /sys/devices/bone_capemgr.*/slots

 0: 54:PF--- 

 1: 55:PF--- 

 2: 56:PF--- 

 3: 57:PF--- 

 4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G

 5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI

 7: ff:P-O-L Override Board Name,00A0,Override Manuf,bspm_P9_42_27

 8: ff:P-O-L Override Board Name,00A0,Override Manuf,bspm_P9_41_27

 9: ff:P-O-L Override Board Name,00A0,Override Manuf,am33xx_pwm

11: ff:P-O-L Override Board Name,00A0,Override Manuf,BB-SPIDEV0

• SPI is ready to go.  py-spidev is already installed, so back to the original instructions, except, we are running a different SPI, so some adjustments are needed
• In this repository : https://github.com/hackerspaceshop/RaspberryPI_WS2801_Bridge/tree/master/software. Download the LedStrip_WS2801.py file to your BB. Edit LedStrip_WS2801.py and change self.spi.open(0, 1) to self.spi.open(1, 1) since we are using a different SPI device. You can use the demo.py to have an idea of what you can do with the library.
• HW time : make sure your led strand is correctly powered (http://learn.adafruit.com/adalight-diy-ambient-tv-lighting/wiring-1 if you need help). Wire the led strand input to your BB : GND goes to pin 1 of P9, CO to pin 22 of P9, DO to pin 18 of P9.
• Finally run python demo.py

I powered the string off of a 5V supply and controlled it with the bone at 3.3V.  This worked fine for about 90 LEDs, after that the colors weren't right.  I'm going to try a level converter to see if I can control a string of 240 LEDs.

--Mark

[1] http://beagleboard.org/latest-images/