> Gesendet: Samstag, 03. Februar 2024 um 01:29 Uhr
> Von: "Jacob Rush" <jr...@phase2it.com>
> I wonder what would happen if you added the source code.
Hi Jacob,
I added all in src that ends with .comp or .hal. This is what now happened. I
was a bit surprise by the emphasis on Python.
Best,
Steffen
User
Can you give an example program for HAL that I can use without hardware
attached to my computer?
GPT
Certainly! A simple HAL (Hardware Abstraction Layer) example in LinuxCNC
doesn't necessarily need to interact with actual hardware. Instead, it can
simulate a scenario or handle software-only interactions. Here's a basic
example that demonstrates creating a HAL component in Python that toggles a
signal back and forth, simulating a simple digital input/output scenario
without requiring any physical hardware.
This example uses a Python HAL component (toggle.py) that creates a HAL pin and
toggles its value between true (1) and false (0) every second. This could
simulate, for example, a sensor being activated and deactivated.
Step 1: Create the Python HAL Component (toggle.py)
First, create a Python file named toggle.py with the following content:
python
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import hal, time
# Create a new HAL component named "toggle"
h = hal.component("toggle")
# Add a pin named "signal" of type bit (boolean) that is an output
h.newpin("signal", hal.HAL_BIT, hal.HAL_OUT)
# Initialize the component
h.ready()
try:
# Main loop to toggle the signal
while True:
# Toggle the signal pin
h['signal'] = not h['signal']
# Print the current state to the console (optional)
print("Signal is now", h['signal'])
# Wait for 1 second before toggling again
time.sleep(1)
except KeyboardInterrupt:
# Handle the user pressing CTRL+C gracefully
print("Exiting toggle.py")
Step 2: Load the Component into LinuxCNC
You will need to integrate this Python component into your LinuxCNC
configuration. Assuming you're running LinuxCNC in a simulated environment (no
actual hardware), you can add the component to your HAL file typically
associated with your LinuxCNC configuration.
Edit Your HAL File: Open the HAL file you're using with your LinuxCNC
configuration, often found in your LinuxCNC configuration directory
(your_config_name.hal).
Load the Python Component: Add the following line to load the toggle.py script
as a HAL component:
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loadusr -W python toggle.py
This command assumes toggle.py is in the same directory as your HAL file or in
a location that's in your system's PATH. The -W option waits for the script to
initialize before proceeding.
Run LinuxCNC: Start your LinuxCNC configuration as you normally would. You
should see messages printed to the terminal showing the signal pin being
toggled between 1 and 0 every second.
Conclusion
This example demonstrates a basic use of HAL in LinuxCNC to simulate a digital
input/output without actual hardware. It's a starting point for more complex
interactions where you can simulate signals and behaviors before integrating
real hardware components.
User
How would you describe that logic of toggle.py in HAL directly, i.e. without
falling back to Python?
GPT
Describing the logic of toggle.py (a Python script that toggles a signal every
second) directly in HAL without using Python involves creating a HAL component
that utilizes existing functionalities within LinuxCNC to achieve the toggle
effect. In HAL, there isn't a direct method to create timed loops as in Python;
however, you can achieve a similar outcome by using a combination of HAL
components that are provided by LinuxCNC, such as a signal generator and a
bit-wise XOR gate.
Here is a conceptual approach to replicate the toggling behavior:
Step 1: Generate a Periodic Signal
First, you would need a signal that changes state periodically. LinuxCNC's hal
library includes a siggen component that can generate a square wave, which
alternates between high and low states at a defined frequency.
shell
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loadrt siggen # Load the signal generator component
addf siggen.0 servo-thread # Attach it to a servo thread for periodic updates
Step 2: Configure the Signal Generator
Configure the siggen to generate a square wave with a period of 2 seconds (0.5
Hz frequency) so that the signal toggles every second. The siggen component
outputs a float, but for a toggle, you only need a high (1) or low (0) signal.
Therefore, the setup might need an additional step to convert this to a bit.
shell
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setp siggen.0.square 0.5 # Set the frequency for a square wave
Since siggen outputs float values, and direct conversion to a binary signal
(bit) for toggling isn't straightforward without a custom component or Python,
this approach illustrates the conceptual setup. In actual HAL usage, especially
for binary toggling, a Python script or a custom C component is often more
practical.
Step 3: Additional Steps for Binary Toggling
To convert the siggen output to a binary toggle signal, you would typically use
a HAL component that can threshold the float signal to a binary one. However,
LinuxCNC's standard HAL components focus on motion control and IO handling, and
such a specific "float-to-bit for toggling" behavior might not be directly
available.
Step 4: Conclusion and Alternative
Due to these limitations, for tasks that require specific timing and toggling
behaviors not directly supported by existing HAL components, using a Python
script (as initially shown) or writing a custom HAL component in C that
encapsulates the desired logic is the recommended approach.
In practical terms, the simplicity of the Python example underscores the
flexibility and power of using higher-level languages for certain types of
logic and control within the LinuxCNC environment, especially when dealing with
logic or control patterns not directly supported by the standard HAL components.
For precise toggling and timing without external scripting, a custom C
component or creative use of existing HAL components and parameters tailored to
the specific needs of your project would be necessary. LinuxCNC's extensive
documentation and community forums can be invaluable resources for finding
examples and advice on creating such custom solutions.
User
Please then round up your overview on simple HAL programming with an example
for toggle that falls back on C.
GPT
Creating a simple HAL component in C to toggle a signal every second requires a
bit more setup than the Python example, but it's a great way to understand how
HAL components are structured and interact with LinuxCNC. Below is a basic
example of how to create a HAL component in C that toggles a HAL bit every
second.
Step 1: Create the HAL Component Source Code
Save the following code as toggle.c. This example creates a HAL component named
toggle with one output pin signal. It toggles this signal every second.
c
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#include "hal.h"
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
static int comp_id; // Component ID
static hal_bit_t *signal; // Pointer to the signal pin
// Function to update the toggle state
void update(void *arg, long period) {
static int counter = 0;
if(counter++ >= 1000) { // Assuming a 1ms thread
*signal = !*signal; // Toggle the signal
counter = 0;
}
}
int rtapi_app_main(void) {
int res;
// Initialize the component
comp_id = hal_init("toggle");
if(comp_id < 0) return comp_id;
// Allocate the memory for the signal pin
res = hal_pin_bit_new("toggle.signal", HAL_OUT, &signal, comp_id);
if(res < 0) goto error;
// Register the update function
res = hal_export_funct("toggle.update", update, NULL, 0, 0, comp_id);
if(res < 0) goto error;
// Ready the component
hal_ready(comp_id);
return 0;
error:
hal_exit(comp_id);
return res;
}
void rtapi_app_exit(void) {
hal_exit(comp_id);
}
This code creates a HAL component that must be compiled and loaded into
LinuxCNC. It uses a simple counter to manage the timing based on the assumption
that it will be attached to a 1kHz thread, which is a common setup.
Step 2: Compile the Component
To compile this component, you need to have the LinuxCNC development files
installed. Compilation is done using the halcompile utility provided by
LinuxCNC. Run the following command in the terminal:
bash
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halcompile --install toggle.c
This command compiles toggle.c into a HAL module and installs it so it can be
loaded by LinuxCNC.
Step 3: Load the Component in LinuxCNC
After compiling, you can load your new toggle component into LinuxCNC using a
HAL file in your LinuxCNC configuration directory. Add the following lines to
your HAL file:
hal
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# Load the toggle component
loadrt toggle
# Add the toggle.update function to a thread
addf toggle.update servo-thread
Make sure to replace servo-thread with the name of the actual thread you want
to run the toggle function in your configuration. This typically would be a
1kHz thread if you want the toggle to happen every second, as the logic in
update function is based on this rate.
Step 4: Test the Component
Start LinuxCNC with your configuration and observe the toggle.signal pin
toggling every second using halshow or halmeter.
This example demonstrates the basic structure for creating a HAL component in C
for LinuxCNC. It provides a starting point for more complex components and
interactions with the physical or simulated machinery.
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