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• Displaying images on the terminal

  Balazs • 10/18/2023 at 17:57 • 0 comments

  This is a crude and very slow solution to show images on the Terminal from within the Linux command line using a custom escape code and a simple Python program.

  // Usage

  path/to/primg.py -[options] path/to/image.jpg
  
  Options:
  -w    horizontal size (default 300)
  -h    vertical size (default 200)
  -s    max. 100x100 pixel
  -l    max. 600x400 pixel

  // primg.py (requires the pillow library)

  #!/bin/python3
  
  from sys import argv
  from PIL import Image
  
  screen_x = 300
  screen_y = 200
  
  # get arguments
  def get_args():
      global screen_x
      global screen_y
      for i in range(1, len(argv)):
          if argv[i] == "-w":
              w = int(argv[i+1])
              if w <= 600 and w > 0:
                  screen_x = w
          elif argv[i] == "-h":
              h = int(argv[i+1])
              if h <= 400 and h > 0:
                  screen_y = h
          elif argv[i] == "-s":
              screen_x = 100
              screen_y = 100
          elif argv[i] == "-l":
              screen_x = 600
              screen_y = 400
      return argv[-1]
  
  # print pixel data to stdout
  def rgb_to_stdout(image):
  #    img = image.convert(mode="RGBA")
      img_x, img_y = img.size
      print("{0}[{1};{2}z".format(chr(27), img_x, img_y), end="")
      for y in range(0, img_y):
          for x in range(0, img_x):
              r, g, b = img.getpixel((x, y))
              r = r // 8
              if r == 10:
                  r = 11
              g = g // 4
              if g == 10:
                  g = 11
              b = b // 8
              if b == 10:
                  b = 11
              print("{0}{1}{2}".format(chr(r), chr(g), chr(b)), end="")
  
  # rotate image if necessary
  def check_rotation(img):
      x, y = img.size
      if ((screen_x > screen_y) and (y > x)) or ((screen_x < screen_y) and (y < x)):
          return img.rotate(90, expand=True)
      else:
          return img
  
  # scale image
  def rescale(img):
      x, y = img.size
      scale_x = x / screen_x
      scale_y = y / screen_y
      if scale_x > scale_y:
          return img.resize((screen_x, int(y / scale_x)))
      else:
          return img.resize((int(x / scale_y), screen_y))
  
  # program entry
  path = get_args()
  img = Image.open(path, "r")
  img = check_rotation(img)
  img = rescale(img)
  rgb_to_stdout(img)
  

   // Details

  Three weeks ago the idea struck me, that I could try to send pixel values over UART from the NanoPi to the Pico and write them directly to the DDRAM of the RA8875. This solution involves a custom escape code (ESC [ (size_x ); (size_y) z) and printing the pixel RGB565 values as characters to stdout. The terminal expects exactly three times the number of pixels as characters after the escape code and keeps writing the values to the DDRAM of the RA8875 until all pixels are received. Printing values over 127 as character to stdout results in an UTF-8 encoding. Because of this, the RGB values are converted to 565 bit format before using the chr() function. After some trial and error I figured out, that print(chr(10)) didn't work, so I simply change the channel value to 11 if it would be 10.

• Setting TERM in .bashrc and using tmux

  Balazs • 08/26/2023 at 12:01 • 0 comments

  Setting the TERM variable or the terminal size in .bashrc leads to some issues in tmux. By default, TERM is "vt220" in DietPi while using UART. This is a possible workaround that can be added to .bashrc:

  if [ $TERM = vt220 ]; then
      TERM=linux
      stty cols 100 rows 30
  fi

  This way TERM doesn't change if it was set by tmux (in my case it is "tmux-color256"). This can also be used to add lines that shouldn't be executed every time you open a new window in tmux.

• Prototyping addon

  Balazs • 08/10/2023 at 12:56 • 0 comments

  I am still looking for inspiration for possible extension modules for this project. In the meantime I started to design a prototyping addon.

• Getting WiringNP to work in DietPi

  Balazs • 08/02/2023 at 11:16 • 0 comments

  FreindlyElec has its own WiringPi based library called WiringNP. It compiles with several warning massages. Trying to execute "gpio readall" in DietPi returns an error massage:

  piBoardRev: Unable to determine board revision from /proc/cpuinfo
   -> Is not NanoPi based board.
   -> You may want to check:
   -> http://www.lemaker.org/
  open /sys/class/sunxi_info/sys_info failed

  While /proc/cpuinfo looks good in DietPi, sys/class/sunxi_info/sys_info doesn't exist. According to this workaround, you can redirect WiringNP to /etc/sys_info by editing WiringNP/wiringPi/boardtype_friendlyelec.c before executing ./build.

  Original:

  if (!(f = fopen("/sys/class/sunxi_info/sys_info", "r"))) {
          LOGE("open /sys/class/sunxi_info/sys_info failed.");
          return -1;
      }

  Modified:

  if (!(f = fopen("/sys/class/sunxi_info/sys_info", "r"))) {
      if (!(f = fopen("/etc/sys_info", "r"))) {
          LOGE("open /sys/class/sunxi_info/sys_info failed.");
          return -1;
      }
  }

  In FriendlyCore for the NanoPi NEO Air sys_info looks like this:

  sunxi_platform    : sun8iw7p1
  sunxi_secure      : normal
  sunxi_chipid      : unsupported
  sunxi_chiptype    : unsupported
  sunxi_batchno     : unsupported
  sunxi_board_id    : 2(0)
  board_manufacturer: FriendlyElec
  board_name        : FriendlyElec Nanopi-NEO-Air

  With this workaround "gpio readall" returns the expected output:

   +-----+-----+----------+------+---+-NanoPi-NEO-Air--+------+----------+-----+-----+
   | BCM | wPi |   Name   | Mode | V | Physical | V | Mode | Name     | wPi | BCM |
   +-----+-----+----------+------+---+----++----+---+------+----------+-----+-----+
   |     |     |     3.3V |      |   |  1 || 2  |   |      | 5V       |     |     |
   |  12 |   8 |  GPIOA12 | ALT5 | 0 |  3 || 4  |   |      | 5V       |     |     |
   |  11 |   9 |  GPIOA11 | ALT5 | 0 |  5 || 6  |   |      | 0v       |     |     |
   | 203 |   7 |  GPIOG11 |  OFF | 0 |  7 || 8  | 0 |  OFF | GPIOG6   | 15  | 198 |
   |     |     |       0v |      |   |  9 || 10 | 0 |  OFF | GPIOG7   | 16  | 199 |
   |   0 |   0 |   GPIOA0 |  OFF | 0 | 11 || 12 | 0 |  OFF | GPIOA6   | 1   | 6   |
   |   2 |   2 |   GPIOA2 |  OFF | 0 | 13 || 14 |   |      | 0v       |     |     |
   |   3 |   3 |   GPIOA3 |  OFF | 0 | 15 || 16 | 0 |  OFF | GPIOG8   | 4   | 200 |
   |     |     |     3.3v |      |   | 17 || 18 | 0 |  OFF | GPIOG9   | 5   | 201 |
   |  64 |  12 |   GPIOC0 |  OFF | 0 | 19 || 20 |   |      | 0v       |     |     |
   |  65 |  13 |   GPIOC1 |  OFF | 0 | 21 || 22 | 0 |  OFF | GPIOA1   | 6   | 1   |
   |  66 |  14 |   GPIOC2 |  OFF | 0 | 23 || 24 | 0 |  OFF | GPIOC3   | 10  | 67  |
   +-----+-----+----------+------+---+----++----+---+------+----------+-----+-----+
  ...

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