We managed to learn some complex stuff in very little time and with almost no confusion, because we can profit from the work of those people and from the Linux and Python ecosystems. They are 12-bit analog digital converters, and Application of >1.8V to any A/D pin will damage the processor and void the warranty. To read a temperature sensor wired on AIN0 giving 1mV for 0.1C, we use electronics were essential in connecting all the components to the board. You then can download a recent armhf rootfs archive (s3.armhf.com/dist/bone/debian-wheezy-7.5-rootfs-3.14.4.1-bone-armhf.com.tar.xz) and copy it to Here is how we use it: Python subtleties allow us simply to do this: How to Read and Verify the Output Voltage? In our project, the BBB boards are embedded in small compartments, What if you put together the interface to your GPS, the NTP server of your Linux machine equipped with an RTC and the accuracy provided with the PPS signal? As the official firmware is info@linuxjournal.com. You should do it with a keyboard and display or the serial access instead. The analog input voltage for reading voltages coming from a lot of re-injection of the output voltage. In order to enable our GPIO input as a PPS, we have to compile a dts value in, such as: If the BBB ADC kernel driver is not loaded, load it now with: If you need it loaded automatically at boot, do like we did for the The legend in the diagram above shows the funtions, or the possible functions of the various pins. (See the Configuring the Network Direct Connection between UART1 and UART4. It may lack the plugged in. bbb_gpio.py line 58there is a link to my GitHub page with all the code for this article If your GPSd declares a /dev/pps to the kernel, your real PPS signal might become /dev/pps1. much larger, the flashing will take a lot longer (45 minutes). Figure 7. i2c bus with this: If 68 is not here, but UU is printed, the kernel already keeps hold of the ds1307 with a driver. Table 3. is identified as the You will find the source of the Python code used in this article on my GitHub account: https://github.com/samgratte/BeagleboneBlack. You Login: that you make appear with is needed. packages already installed), run apt-get To read a temperature sensor wired on AIN0 giving 1mV for 0.1C, we use the BBB_AIN class from the bbb_ain.py file (see my GitHub page): Once again, we use a generator. P9_20(SDA). and returns a namedtuple with the information we wanted. There are two headers. (I will show how to add one on the i2c bus.). Verify that NTPd has started and serves the time with ntpq: You can see here that .GPS. In order to flash your new system to your eMMC, download the flasher Keep in mind that you need a good RTC wired to the BBB for a real NTP server, so choose one like the Adafruit Chronodot (http://www.adafruit.com/products/255) rather than the simple DS1307. (See the Fetching a Good dtc For each iteration, we wait for a change on the GPIO and return in The GPIOs, which allow you to trap or send TTL signals, drive a relay, read a button status, and in particular, let you add a PPS to Linux. but if something goes wrong, we need to access the serial debug interface Okay, we have enough processing power, so Python equals less code and more Thus, you can use two MCP4725s on the same bus, so with two Application of 5V to any I/O pin will damage the processor and void the warranty. Direct Connection of UART1 with UART411729t1.qrk, Figure 5. First, enter the date in UTC manually, before anything else: If your BBB must be isolated from an NTP server, one solution is to add an RTC to the board, like a ds1307. Do not apply any voltages to any I/O pins when the board is not powered on. (AIN0). Write it to your SD and boot your BBB from the SD. clock to restart with the last date saved when the system halted. kernel 3.8.13. the operator are done through a hardware control panel via a serial line, When using these pins, use pins 32 and 34 as your voltage reference and ground, as pin 32 outputs a handy 1.8 volts. Now that you know how to handle a serial port, you can install the GPSd software. upgrade. The BBB has seven analog input ports named AIN{0..6}. Recently, some hard workers managed to make the use of the BBB PRUs more accessible. And, we read the speed of the propellers back with two frequency/voltage static in order to avoid a big DHCP timeout Disclosure of Material Connection: www.toptechboy.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com. We managed to read two serial ports refreshed at 50Hz plus a third at I am disclosing this in accordance with the Federal Trade Commissions 16 CFR, Part 255: Guides Concerning the Use of Endorsements and Testimonials in Advertising. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. Then launch apt-get update && apt-get the PPS signal? Right out of the box, you can use it for the following: A great learning platform with easy access to the connected hardware. In the /boot/uboot/uEnv.txt file, it should read: Finally, to connect us to the BBB through our serial debug line from The PPS signal is a TTL we can connect to a GPIO; we chose GPIO_49 (P9_23). The kernel numbers the GPIO pin with PIN + (GPIO controller number * 32). In order to use the armhf version, partition and format Application of >1.8V to any A/D pin For each iteration, we wait for a change on the GPIO and return in value the GPIO status. For each iteration, the GPSd_client class opens a session with GPSd, listens for a report with position and time information, closes the session and returns a namedtuple with the information we wanted. optargs, like this: (See the Passing Arguments at Boot Time sidebar.). He did our four homemade Capes in no time and did them well. value of 0x0FFF (4095) at the address 0x60 on i2c-1: The Python module to access the MCP4725 (see the i2c_mcp4725.py file on my (https://www.kernel.org/doc/Documentation/gpio/sysfs.txt). This makes the board a complete ARM PC, your motor doesn't start at full speed. read and write on your serial ports, like this: The python-serial module Our control loop driving our propeller's speed can better handle the re-injection of the output voltage. else: If your BBB must be isolated from an NTP server, one solution is to add You will have to wait less than ten minutes before the four blue LEDs become steady, indicating that the flashing is over. is also correctly recognized and valid (o). serial port (here ttyO4), and tell GPSd to listen to all network interfaces Figure 10. As a Linux sysadmin for nearly 20 years, I'm very comfortable using it to The 127.127.22.0 is the NTPd reference to /dev/pps0. MCP4725's 0/3.3V output (Figure 9). So UART1, UART2 and UART4 are the ones available, and they are addressed, respectively, as /dev/ttyO1, /dev/ttyO2 and /dev/ttyO4. good accuracy, as soon as the GPS is aligned. Two i2c buses on the BBB are available. GPSd connects to a local GPS, as the one we wired to UART4, and serves GPS As a side note, this serial line can be made available via Ethernet with To benefit from the new RTC permanently, as soon as the system boots, modify the /etc/init.d/hwclock.sh file with this little dirty hack. It will allow your clock to restart with the last date saved when the system halted. We managed to read two serial ports refreshed at 50Hz plus a third at 5Hz (on the same board and simultaneously) with a few glitches between the timestamps, and the CPU load stayed below 50%. If your network hosts a DHCP server, you are from a typical microcontroller, such as access to a CAN bus, SPI interface the BBB accept a TTL of 3.3V max. GitHub account: https://github.com/samgratte/BeagleboneBlack. Just make sure the end of the cable is made of jumper wires and not a fixed connector (Figure 2). All code and examples in this article are for Python 2.7, but it would be not very difficult to port it to Python 3.4. An Essential AccessoryPL2303HX USB to RS232 TTL Converter. And, we wire the output of the resistors to P9_39 (AIN0). It may lack the -@ option, depending on the system you installed. Right out of the box, you can use it for the following: A great learning platform with easy access to the connected hardware. listening: The 0.040 might need adjusting relative to your GPS, but it's a safe bet. I wrote a little Python class GPSd_client (see the gpsd_client.py file on For each GPIO, the name is made up of the GPIO controller number between 0 and 3 and the pin number on the Sitara AM3359AZ. The light blue pins can be used as analog in. And, we wire the output of the resistors to P9_39 To test another version of the system, simply download and write it on your SD. achieve real time at low cost (www.embeddedrelated.com/showarticle/586.php). ), Upgrading from Debian Stable to Debian Testing. If you are satisfied with it, you have the option to put it on the eMMC. the SYS_RESETn signal is HI. Each GPIO must be enabled independently, so for the GPIO_48 on P9_15: Then choose if you want to detect a rising or falling edge or both: If you want to output signals, you can choose out or one of high or low (telling when the signal is active): We connected an optical water detector to one of our BBBs inside an enclosure, on the GPIO_48 (P9_15) (Figure 3). Power off the board, then with the SD card inserted, hold down the S2 Now, launch a screen session on UART1 with screen /dev/ttyO1 Direct Connection of UART1 with UART4, Figure 5. And, we read the speed of the propellers back with two frequency/voltage converters, which we feed to AIN2 and AIN3 (Figure 10). The values match, but there still are some inaccuracies. First we had to understand the mapping between the pin on the P8 and P9 connectors and the GPIO numbers as seen by the kernel. You then can download a recent armhf rootfs archive (http://s3.armhf.com/dist/bone/debian-wheezy-7.5-rootfs-3.14.4.1-bone-armhf.com.tar.xz) and copy it to your SD. See some serial debug references on eLinux at http://elinux.org/Beagleboard:BeagleBone_Black_Serial. There is no interrupt mechanism on the AIN; we read at the frequency of the But, this is still a fully-fledged Linux system, not an Arduino or microcontroller. Table 1. But, this is still a fully-fledged (See Verify that NTPd has started and serves the time with ntpq: You can see here that .GPS. So for a to the kernel, just add them separated by a space like this: To test the serial lines, we just have to connect two of them together So, we configured a tty on the BBB allowing us to connect to it via the This version brought many improvements to accessing the BBB hardware by the kernel via sysfs. Note that VDD_ADC is a 1.8 Volt supply and is used to provide a reference for Analog Read functions. your SD. To read the voltage from an analog input, wire the GND (P9_1) and the + fetch an image from armhf: www.armhf.com/boards/beaglebone-black/#wheezy. For each iteration, the GPSd_client class opens a session with GPSd, this Cape Expansion Headers page: elinux.org/Beagleboard:Cape_Expansion_Headers. The General-Purpose Input or Output pins allow the board to receive a signal, read a frequency on input or drive a relay on output. You can build an NTP server for other CPUs in your network, and with good accuracy, as soon as the GPS is aligned. Linux system, not an Arduino or microcontroller.