traumverloren/rpi3-hints.md

## rpi3-hints.md

      
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              rpi3-hints.md
            
          
    Get file off RPI:

 scp pi@rpi3.local:~/tfjs-yolo-tiny/demo/test.jpg ~stephanie/Desktop
Serial Ports

Disable console on serial ports:


sudo raspi-config
Select option 5, Interfacing options, then option P6, Serial, and select No. Exit raspi-config.

Ensure cmdline.txt config:


sudo nano /boot/cmdline.txt
Make sure it doesn't include: console=ttyAMA0,115200 (fyi, this is ok: console=tty1)

Update config.txt:


Add enable_uart=1. This assigns the mini UART (serial1) to the Bluetooth module, since we are using serial0 now as our main serial for the GPIO pins.
Disable BT to be safe: dtoverlay=pi3-disable-bt

Check state of pins 15 & 16 of GPIO:

Ensure UART pins 15,16 are in state ALT0.

Install wiringpi: sudo apt-get install wiringpi
gpio readall
Change to ALT0 if they aren't:

gpio mode 15 ALT0
gpio mode 16 ALT0

Reboot and test it:


sudo reboot
sudo minicom -D /dev/serial0 (should be able to type in console)
Run python test_uart.py

#!/usr/bin/env python
# test_uart.py
# Will also work on Python3.
# Serial port loopback testing for a RaspberryPi.

from __future__ import print_function
import serial

test_string = "Testing 1 2 3 4".encode('utf-8')
#test_string = b"Testing 1 2 3 4" ### Will also work

port_list = ["/dev/serial0", "/dev/ttyAMA0", "/dev/serial1", "/dev/ttyS0"]

for port in port_list:

    try:
        serialPort = serial.Serial(port, 115200, timeout = 2)
        serialPort.flushInput()
        serialPort.flushOutput()
        print("Opened port", port, "for testing:")
        bytes_sent = serialPort.write(test_string)
        print ("Sent", bytes_sent, "bytes")
        loopback = serialPort.read(bytes_sent)
        if loopback == test_string:
            print ("Received", len(loopback), "valid bytes, Serial port", port, "working \n")
        else:
            print ("Received incorrect data", loopback, "over Serial port", port, "loopback\n")
        serialPort.close()
    except IOError:
        print ("Failed at", port, "\n")

Update rc.local if gpio 15 & 16 not staying in ALT0 mode:


sudo nano /etc/rc.local
Add before exit 0:

gpio mode 15 ALT0
gpio mode 16 ALT0

Resources:

https://www.raspberrypi.org/documentation/configuration/uart.md
https://blainebooher.com/jekyll/update/2018/05/15/pi3-btle.html
NodeJS mem mgmt


Increase swap size to 1024mb (https://wpitchoune.net/tricks/raspberry_pi3_increase_swap_size.html)

sudo dphys-swapfile swapoff
sudo nano /etc/dphys-swapfile & CONF_SWAPSIZE=1024, save.
sudo dphys-swapfile setup
sudo dphys-swapfile swapon
check with htop (https://www.bitpi.co/2015/12/30/htop-linux-task-manager/)


node --max-old-space-size=500 index.js  <--- rpi has 1gb ram, this will tell node that GC needs to happen sooner around 500mb (https://stackoverflow.com/questions/40214669/raspberry-pi-3-script-ram-usage)


Or to remove SWAP completely (https://medium.com/@meeDamian/bitcoin-full-node-on-rbp3-revised-88bb7c8ef1d1):


Turn off PM2:


pm2 unstartup
[PM2] Init System found: systemd
[PM2] To setup the Startup Script, copy/paste the following command:
sudo env PATH=$PATH:/usr/bin /usr/lib/node_modules/pm2/bin/pm2 unstartup systemd -u pi --hp /home/pi


BACKUP RPI SD CARD:

(https://appcodelabs.com/how-to-backup-clone-a-raspberry-pi-sd-card-on-macos-the-easy-way)

diskutil list should be /dev/disk2
make a folder:
cd ~
mkdir rpi_backups
cd rpi_backups


copy from sd card to mac: sudo dd if=/dev/rdisk2 of=rpi_yolo_nodejs_backup_jul_6_2019.dmg
format new SD card using SDformatter application on Mac
check new SD card: diskutil list
Then unmount the SD card: diskutil unmountDisk disk2
Then copy backup file to SD card: sudo dd if=rpi_yolo_nodejs_backup_jul_6_2019.dmg of=/dev/rdisk2