E3D Support: PZ probe

Preset	Threshold (Sensitivity)	Filter (Fc=260, F_BW=50)	300 mm/min	500 mm/min	700 mm/min	900 mm/min	12000 mm/min
0	5	Off	0.005	FT	FT	FT	FT
1	10	Off	0.005	0.005	0.015	0.020	0.130
2	15	Off	0.005	0.005	0.015	0.025	0.140
3	1	Off	FT	FT	FT	FT	FT
4	5	On	0.050	0.050	0.100	0.105	0.150
5	10	On	0.050	0.080	0.115	0.140	0.225
6	15	On	NT	0.080	0.115	0.110	0.280
7	1	On	0.010	0.045	0.090	0.100	0.145

By pressing the button on the controller, you can switch between 8 pre-configured presets. Seven of these presets are configurable via UART or I2C, while the preset"0" remains as the default and cannot be configured. These can be configured by looking at the Configurations and Commands section fo this guide.

On power up, Preset 0 is used by default. If you choose to change the preset, for example, you choose Preset 2, the PZ Probe Board will power up using Preset 2.

The table below shows the default values for each of the presets:

Preset	Threshold	Trigger Direction	Filter Active	Filter Centre Frequency	Filter Bandwidth	Safety Trigger Active
0	5	1	0	260	50	1
1	10	1	0	260	50	1
2	15	1	0	260	50	1
3	1	1	0	260	50	1
4	5	1	1	260	50	1
5	10	1	1	260	50	1
6	15	1	1	260	50	1
7	1	1	1	260	50	1

Preset – Which preset setting you are in. Values shown in the table to the right of Preset are associated with the preset setting The preset that is being used can be changed easily by pressing the button on the PCB. The preset state is recovered after power cycling the PCB.
Threshold – This sets the sensitivity of controller (smaller number is more sensitive). The threshold value directly correlates to the 12-bit ADC, so if a threshold of 10 is set, the controller waits until the ADC reads a signal that is 10 or higher to trigger.
Trigger direction – This determines if the trigger is a rising-edge or a falling-edge trigger. This will usually be a rising-edge trigger in this application as the PZ Probe provides a pulse in the positive direction when compressed. Note: This does not change the output polarity.
Filter Active – This activates the IIR filter (1) or deactivates (0) the filter. The filter has two parameters; Centre Frequency and Bandwidth which are discussed below. This is useful to activate when noise from the heatsink fan interferes with triggering.
Filter Centre Frequency – This stores the value of the frequency of the noise that is to be cancelled out.
Filter Bandwidth – This stores the value of the range of frequency away from the centre frequency that should be cancelled out.
Safety Trigger Active – This should always be set to 1 as it ensures that the controller outputs the trigger state during UART or I2C communications to reduce the chance with a collision with the bed. This can be switched off, if this behaviour isnt desired.
Output Polarity * From board Batch 5792 (see back of PCB) – This determines the behaviour of the trigger signal that goes to the printer. It can be set to be either active high (1) or active low (0). Active low means that the output signal falls from from High to Low when triggered and active high means that the output signal rises from Low to High when triggered.

Preset	LED 3	LED 2	LED 1
Default (0)	Off	Off	Off
1	Off	Off	On
2	Off	On	Off
3	Off	On	On
4	On	Off	Off
5	On	Off	On
6	On	On	Off
7	On	On	On

If the default preset settings are not suitable for you setup, you can fine-tune them by modifying the presets with custom settings. There are five different ways to configure your PZ Probe, allowing you to choose the option that best suits you. Once configured, you can choose to disconnect UART as your values will be saved in memory and will be retained on power cycle.

All the options below use UART as this is the preferred method of communication. All methods will require the following hardware connections between the PZ Probe Board and the communication device:

Comm Device PZ Probe Board

5V/3V3 ----------- PWR
GND ------------- GND
RX --------------- TX
TX --------------- RX

This method of configurating requires the UART pins (RX/TX) to be connected to the pin header of the Raspberry Pi. When doing so, ensure that the power of PZ Probe Board is connected to the 3.3V.

If you are using the Raspberry Pi on your 3D printer and PWR, GND and TRIG are connected to the printer control board, then only RX/TX have to be connected to the Raspberry Pi. The printer control board must by 3.3V to do this method.

1. Power up and login to your Raspberry Pi. If UART isn't already active, activate it in Raspi-config.

2. Within the terminal, type in:
sudo nano /boot/cmdline.txt

3. Delete the serial console parameter, it may look something like this:
console=serial0,115200
Then save and exit the file.

4. Create a python script. This can be done within the terminal by typing:
nano piezo_config_config.py
Copy the code from below and paste it within the piezo_config.py file:

piezo_config_config.py

5. Save the file and exit the nano editor.

6. In the terminal, ensure you are in the same directory as the python script and type:
python piezo_config.py

7. The script will then ask you to enter a command. Use the Commands tab to type in a particualar command you wish to use. The script will execute the command and send any replies to the terminal. The scipt will end when there are no more messages recieved from the PZ Probe Board after 2 seconds.

In the image below, an example of communicating with the PZ Probe Board via the Raspberry Pi Terminal can be seen:

Gary_Terminal.png__PID:df02a9c8-84fd-40ff-8f61-9a829c3df06e

Line 1: shows the command to start the python script.
Line 2: the scipt asks what message to send. The message is then typed in.
Line 3-6: shows the response from the Piezo Controller confirming that the change has been made.
Line 7: shows that the script recieved no further data from the Piezo Controller, so the script was terminated.

If a command didnt't have intended result because a result like "No valid command received, please try again." was provided. Then, please try to rerun the scipt or connect/disconnect the PZ Probe Board.

The script may need to be modified if UART isn't identified as Serial0, You can use ls /dev/serial* in terminal to find the appropriate serial device.

“SET A,BBB,C,D,EEE,FFF,G” – Set command is used to change the settings below. When using this command, make sure to fill in all values. There should be a space only between "Set" and "A," with no spaces between the commas.
“SET A,BBB,C,D,EEE,FFF,G,H” – From board Batch 5792 (see back of PCB) Set command is used to change the settings below. When using this command, make sure to fill in all values. There should be a space only between "Set" and "A," with no spaces between the commas.

A: The Preset (mode). As seven of the modes are configurable, the value of A can only be 1-7, 0 is the default mode and can't be changed.
BBB = Threshold
C = Trigger Direction
D = Filter Active
EEE = Filter Centre Frequency
FFF = Filter Bandwidth
G = Safety Trigger Active
H = Output Polarity From board Batch 5792 (see back of PCB)

These settings are explained in more depth after the list of commands below

“SET X” – This command is used to change the preset (mode), where X is a number between 0 and 7. It performs the same operation as pressing the button on the PZ Probe Board. It will also reply with all the settings being used in status.
“STATUS” – STATUS command is used to determine the current preset state of the PZ Probe Board. It will also reply with all the settings being used in status. This command is especially useful to use before the "SET" command when you only want to change one value.
“REC TRIG” – This troubleshooting command is used to record 1000 reading, among which 100 before the trigger and 900 after. The trigger output stays in a triggered state until all values are printed out over UART. Since readings are taken at approximately 7788Hz, the data can be copied to Excel and estimate a time base accordingly. Only the threshold from the current preset is used with this command, so the filter and trigger direction settings do not affect it.
“REPORT ADC” – This is another useful troubleshooting command, similar to "REC TRIG," but it only records 1000 readings after a 100ms delay and outputs them over UART. The readings are taken at approximately 7788Hz (From board Batch 5792 the data rate is now 3894Hz), so you can copy the data to Excel and estimate a time base accordingly. If there is a noisy fan, an oscillating signal will be visible, allowing you to determine the filter frequency needed to cancel it out. Settings from the current preset is used such as threshold, trigger direction and the filter are used during the use of this command.

Note: these commands are typed in with no quotation marks.

In depth SET Settings explained:

Preset – Which preset setting you are in. Preset 0 is the default state and can’t be modified. Presets 1-7 can be modified by using the “SET” command.
Threshold (input value range: -400 to 400, integers only) – This sets the sensitivity (smaller number is more sensitive). It is recommended to beyond the range of 0-30 as it is likely something else in the system has gone wrong if a value larger than this is required.
Trigger direction (input value range: 0,1) – This should always be 1 (rising-edge trigger) for Revo PZ Probe Voron. However, it can also be changed to 0 (falling-edge trigger). Note: This does not change the output polarity.
Filter Active (input value range: 0,1) – This activates the filter (1) or deactivates (0) the filter. The filter has two parameters; Centre Frequency and Bandwidth which are discussed below. If the filter is used, it is recommended to reduce the threshold as much as possible (1-5 Threshold has worked best in testing).
Filter Centre Frequency (input value range: 0 to 500, units: Hz, integers only) – This should be set to the value of the frequency of the noise you wish to cancel out.
Filter Bandwidth (input value range: 0 to 500, units: Hz, integers only) – This should be set to the error or range of the frequencies around the Centre Frequency you wish to cancel out. For example, if you have a centre frequency of 260Hz and a bandwidth of 50Hz – then the noise between 210-310Hz will be reduced.
Safety Trigger Active (input value range: 0,1) – This should always be set to 1 and it ensures that the controller outputs the trigger state to reduce the chance with a collision with the bed whenever the controller is busy with communications (UART, I2C). If it is set to 0 for experimental reasons, then the printer could move the Z axis and the PZ Probe may not detect the collision.
Output Polarity (input value range: 0,1) From board Batch 5792 (see back of PCB)– Allows for changing the output signal behaviour. 0 indicates an active low trigger, meaning that the output is always high when idle. The output goes low momentarily when Piezo is triggered. 1 indicates an active high trigger, meaning the output is always low when idle. The output goes high momentarily when the Piezo is triggered.

When the triggering of the PZ Board doesn't behave as expected, it is usually down to either false triggering or no triggering.

False triggering refers to the PZ Probe Board giving an output suggesting that the bed has been contacted, even though it hasn't.

No triggering refers to the PZ Probe Board giving no output despite contacting the bed.