spectro-script

Capture script for the UMD Loop spectrometer (STM32 + TCD1304 CCD).

The Jetson (on the rover) has the spectrometer plugged into USB. It runs get_spectro_image.py, which captures CCD frames for 20 seconds (one PNG every 2 seconds), zips them, and SFTPs the zip to the base station at 192.168.88.10.

 ┌─────────────┐   USB CDC    ┌─────────────┐   SFTP (zip)   ┌─────────────────────────┐
 │ Spectrometer│ ───────────▶ │   Jetson    │ ─────────────▶ │      Base station       │
 │ (STM32 CCD) │  /dev/spectro│  (rover)    │  192.168.88.10 │ ~/Desktop/spectro_captures│
 └─────────────┘              └─────────────┘                └─────────────────────────┘

On both machines this lives inside the ~/infrastructure repo, at ~/infrastructure/spectro-script.

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Requirements

Python 3 plus three pip packages (needed wherever you run get_spectro_image.py, i.e. the Jetson — and on any machine you want to test the transfer from):

pip3 install pyserial matplotlib paramiko

Package	Used for
pyserial	reading CCD frames from the USB serial port
matplotlib	rendering each frame to a PNG plot
paramiko	SFTP upload of the zip to the base station

The base station needs no Python packages — just an SSH server (see step 2).

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0. Clone the repo (both machines)

git clone <repo-url> ~/infrastructure
cd ~/infrastructure/spectro-script

Replace <repo-url> with the actual remote. All commands below assume the script is at ~/infrastructure/spectro-script/get_spectro_image.py.

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1. Jetson setup (the machine the spectrometer plugs into)

1a. Python dependencies

sudo apt update
sudo apt install -y python3-pip
pip3 install pyserial matplotlib paramiko   # see Requirements above

1b. Install the udev rule

The spectrometer enumerates as a USB CDC serial port. The udev rule grants non-root access and creates a stable /dev/spectro symlink so the script doesn't depend on the kernel-assigned /dev/ttyACM* number.

cd ~/infrastructure/spectro-script
./install_udev_rule.sh        # self-elevates with sudo

Plug in (or replug) the spectrometer, then confirm:

ls -l /dev/spectro            # should be a symlink to /dev/ttyACM*

If /dev/spectro doesn't appear, verify the device is enumerating with the expected ID (0483:5740):

lsusb | grep 0483

1c. Configure the transfer target

The destination base station and credentials are set at the top of get_spectro_image.py:

REMOTE_HOST = "192.168.88.10"
REMOTE_USER = "umdloop"
REMOTE_PASSWORD = "..."          # base-station SSH password
REMOTE_PORT = 22
REMOTE_DIR = "/home/umdloop/Desktop/spectro_captures"   # created automatically if missing

Make sure these match the base-station account from step 2.

1d. Run it

cd ~/infrastructure/spectro-script
python3 get_spectro_image.py

You should see it capture ~10 frames over 20 seconds, zip them, and report Transfer complete.

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2. Base station setup (192.168.88.10, receives the zips)

The base station just needs to accept SSH/SFTP connections from the Jetson. The script creates REMOTE_DIR automatically, so no directory prep is required.

2a. Make sure an SSH server is running

sudo apt update
sudo apt install -y openssh-server
sudo systemctl enable --now ssh

2b. Confirm the account exists and the IP is correct

• A user matching REMOTE_USER (e.g. umdloop) must exist with the password set in REMOTE_PASSWORD.
• The base station's IP must be 192.168.88.10 (static, or a DHCP reservation). Check with ip addr.

That's it — incoming zips land on the Desktop in ~/Desktop/spectro_captures/ as spectro_<YYYYmmdd_HHMMSS>.zip.

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3. Quick verification (end to end)

1. On the Jetson: python3 ~/infrastructure/spectro-script/get_spectro_image.py
2. On the base station:

   ls -lt ~/Desktop/spectro_captures/ | head

   A new spectro_*.zip should appear. Unzip to view the PNG plots.

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Tuning

All knobs are constants at the top of get_spectro_image.py:

Setting	Default	Meaning
CAPTURE_DURATION_S	20	Total capture time (seconds)
CAPTURE_INTERVAL_S	2	Seconds between saved frames
NUM_PIXELS	6000	Pixels per CCD frame (must match firmware)
PORT	/dev/spectro	Serial device (use COM13 etc. on Windows)

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Notes / troubleshooting

• SFTP transfer failed: ... Authentication failed — wrong REMOTE_USER/REMOTE_PASSWORD, or the base-station account doesn't allow password auth (PasswordAuthentication yes in /etc/ssh/sshd_config).
• SFTP transfer failed: ... timed out — base station unreachable; check the network and that the IP is 192.168.88.10.
• Timeout waiting for FRAME header — the spectrometer isn't streaming; confirm /dev/spectro exists and the firmware is running.
• The password is hardcoded in the script. This is acceptable only because it's a throwaway account on the isolated rover network — don't reuse it elsewhere.