Coordinated Holiday Lights - box 4

The forth box features the BeagleBone Black (bbb), the IoT Relay (I might as well use them since I already have them), and also has hard-wired ethernet. The bbb features TI's AM335x Sitara SoC which is based on a single-core, 32-bit, ARM, Cortex-A8. This device will control the lights on the eastern driveway gate.

Parts:

• BeagleBone Black
• Digital Loggers IoT Relay
• Adafruit ethernet gland (product: 827)
• Wago 221 connectors

Unlike the RPi (or other RPi-like boards), the bbb is quite clear in its documentation that it can not be powered via its expansion pins. Therefore this build uses the 5V transformer that came with the board and plugs into the bbb's mini-B USB connector.

The bbb has both a soldered-on eMMC flash, and takes an SDcard. By default, if the firmware detects a valid image on the eMMC, its preference is to boot from that device over the SDcard. I want to always have my system boot from SDcard. Therefore on first boot I hold down the BOOT button in order to get it to boot from the SDcard and not the eMMC. Once running I then erased the eMMC flash. Without a valid image in eMMC the bbb's firmware will elect instead to boot from the SDcard.

On the one hand it's nice that so many SBCs have standardized around a common header. On the other hand it would have been nicer if the industry had standardized around a header that provided access to more of the buses and pins that projects could use. Of course in my case I only need access to 1 GPIO pin, therefore the standard "RPi 40-pin header" is more than adequate. However some projects can find the 40 pins of the RPi header limiting. If you find yourself in that sort of situation, you'll appreciate the bbb's staggering 92 pins:

Similar to the RPi, the bbb's kernel is well-loved, therefore the kernel knows a lot about its GPIOs:

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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133

root@beaglebone:~# gpioinfo gpiochip0 - 32 lines: line 0: "[ethernet]" unused input active-high line 1: "[ethernet]" unused input active-high line 2: "P9_22 [spi0_sclk]" unused input active-high line 3: "P9_21 [spi0_d0]" unused input active-high line 4: "P9_18 [spi0_d1]" unused input active-high line 5: "P9_17 [spi0_cs0]" unused input active-high line 6: "[sd card]" "cd" input active-low [used] line 7: "P9_42A [ecappwm0]" unused input active-high line 8: "P8_35 [hdmi]" unused input active-high line 9: "P8_33 [hdmi]" unused input active-high line 10: "P8_31 [hdmi]" unused input active-high line 11: "P8_32 [hdmi]" unused input active-high line 12: "P9_20 [i2c2_sda]" unused input active-high line 13: "P9_19 [i2c2_scl]" unused input active-high line 14: "P9_26 [uart1_rxd]" unused input active-high line 15: "P9_24 [uart1_txd]" unused input active-high line 16: "[ethernet]" unused input active-high line 17: "[ethernet]" unused input active-high line 18: "[usb]" unused input active-high line 19: "[hdmi]" unused input active-high line 20: "P9_41B" unused input active-high line 21: "[ethernet]" unused input active-high line 22: "P8_19 [ehrpwm2a]" unused input active-high line 23: "P8_13 [ehrpwm2b]" unused input active-high line 24: "[NC]" unused input active-high line 25: "[NC]" unused input active-high line 26: "P8_14" unused input active-high line 27: "P8_17" unused input active-high line 28: "[ethernet]" unused input active-high line 29: "[ethernet]" unused input active-high line 30: "P9_11 [uart4_rxd]" unused input active-high line 31: "P9_13 [uart4_txd]" unused input active-high gpiochip1 - 32 lines: line 0: "P8_25 [emmc]" unused input active-high line 1: "[emmc]" unused input active-high line 2: "P8_5 [emmc]" unused input active-high line 3: "P8_6 [emmc]" unused input active-high line 4: "P8_23 [emmc]" unused input active-high line 5: "P8_22 [emmc]" unused input active-high line 6: "P8_3 [emmc]" unused input active-high line 7: "P8_4 [emmc]" unused input active-high line 8: "[NC]" unused input active-high line 9: "[NC]" unused input active-high line 10: "[NC]" unused input active-high line 11: "[NC]" unused input active-high line 12: "P8_12" unused input active-high line 13: "P8_11" unused input active-high line 14: "P8_16" unused input active-high line 15: "P8_15" unused input active-high line 16: "P9_15A" unused input active-high line 17: "P9_23" unused input active-high line 18: "P9_14 [ehrpwm1a]" unused input active-high line 19: "P9_16 [ehrpwm1b]" unused input active-high line 20: "[emmc]" unused input active-high line 21: "[usr0 led]" "beaglebone:green:heartbeat" output active-high [used] line 22: "[usr1 led]" "beaglebone:green:mmc0" output active-high [used] line 23: "[usr2 led]" "beaglebone:green:usr2" output active-high [used] line 24: "[usr3 led]" "beaglebone:green:usr3" output active-high [used] line 25: "[hdmi]" "interrupt" input active-high [used] line 26: "[usb]" unused input active-high line 27: "[hdmi audio]" "enable" output active-high [used] line 28: "P9_12" unused input active-high line 29: "P8_26" unused input active-high line 30: "P8_21 [emmc]" unused input active-high line 31: "P8_20 [emmc]" unused input active-high gpiochip2 - 32 lines: line 0: "P9_15B" unused input active-high line 1: "P8_18" unused input active-high line 2: "P8_7" unused input active-high line 3: "P8_8" unused input active-high line 4: "P8_10" unused input active-high line 5: "P8_9" unused input active-high line 6: "P8_45 [hdmi]" unused input active-high line 7: "P8_46 [hdmi]" unused input active-high line 8: "P8_43 [hdmi]" unused input active-high line 9: "P8_44 [hdmi]" unused input active-high line 10: "P8_41 [hdmi]" unused input active-high line 11: "P8_42 [hdmi]" unused input active-high line 12: "P8_39 [hdmi]" unused input active-high line 13: "P8_40 [hdmi]" unused input active-high line 14: "P8_37 [hdmi]" unused input active-high line 15: "P8_38 [hdmi]" unused input active-high line 16: "P8_36 [hdmi]" unused input active-high line 17: "P8_34 [hdmi]" unused input active-high line 18: "[ethernet]" unused input active-high line 19: "[ethernet]" unused input active-high line 20: "[ethernet]" unused input active-high line 21: "[ethernet]" unused input active-high line 22: "P8_27 [hdmi]" unused input active-high line 23: "P8_29 [hdmi]" unused input active-high line 24: "P8_28 [hdmi]" unused input active-high line 25: "P8_30 [hdmi]" unused input active-high line 26: "[emmc]" unused input active-high line 27: "[emmc]" unused input active-high line 28: "[emmc]" unused input active-high line 29: "[emmc]" unused input active-high line 30: "[emmc]" unused input active-high line 31: "[emmc]" unused input active-high gpiochip3 - 32 lines: line 0: "[ethernet]" unused input active-high line 1: "[ethernet]" unused input active-high line 2: "[ethernet]" unused input active-high line 3: "[ethernet]" unused input active-high line 4: "[ethernet]" unused input active-high line 5: "[i2c0]" unused input active-high line 6: "[i2c0]" unused input active-high line 7: "[emu]" unused input active-high line 8: "[emu]" unused input active-high line 9: "[ethernet]" unused input active-high line 10: "[ethernet]" unused input active-high line 11: "[NC]" unused input active-high line 12: "[NC]" unused input active-high line 13: "[usb]" unused input active-high line 14: "P9_31 [spi1_sclk]" unused input active-high line 15: "P9_29 [spi1_d0]" unused input active-high line 16: "P9_30 [spi1_d1]" unused input active-high line 17: "P9_28 [spi1_cs0]" unused input active-high line 18: "P9_42B [ecappwm0]" unused input active-high line 19: "P9_27" unused input active-high line 20: "P9_41A" unused input active-high line 21: "P9_25" unused input active-high line 22: "[NC]" unused input active-high line 23: "[NC]" unused input active-high line 24: "[NC]" unused input active-high line 25: "[NC]" unused input active-high line 26: "[NC]" unused input active-high line 27: "[NC]" unused input active-high line 28: "[NC]" unused input active-high line 29: "[NC]" unused input active-high line 30: "[NC]" unused input active-high line 31: "[NC]" unused input active-high

Arbitrarily, I've decided that I'm going to use GPIO_45. GPIO_45 is located on connector P8, pin 11. Looking through the information provided above we see that P8_11 is found at gpiochip1, line 13. No datasheets, schematics, or reference manuals required! Wiring up a prototype, we can perform the following quick test:

1	root@raspberrypi3-64:~# gpioset gpiochip1 13=1

Wait a minute! The load didn't turn on, why aren't the lights on after running the above command?

At first I assumed I had done something wrong: bad wiring or maybe bad GPIO? I checked all the wiring; looks okay. Then I tried a different GPIO; same result. Maybe try a GPIO on the P9 connnector; still doesn't work. One of the times I ran the gpioset program I did hear the relay click, although the lights didn't turn on, which led me to believe I had found the correct GPIO/pin association. After a bit of searching around I came across the --mode=wait option of gpioset.

As long as the gpioset program is running, it will control the GPIO line, but when it terminates, it releases the line. Coincidentally, on all the other SBCs I've used so far, after gpioset terminates, the line stays where it had been set. As a result the lights are turned on and stay on. On the bbb, however, after the gpioset program terminates the GPIO line doesn't continue on in the state in which it was set, rather it returns to its previous "OFF" state. Since code is fast and relays are slow, most times the relay doesn't even click over (never mind the lights coming on) before the relay is de-activated. Therefore when testing gpio lines with gpioset, it would be best to test with the following and then terminate the program with Ctrl-C:

1	root@raspberrypi3-64:~# gpioset --mode=wait gpiochip1 13=1

fritzing:

finished box:

before install:

after install: