User Manual

PD28-1-1021 / PD28-3-1021 V1.4 Hardware Manual (Rev. 1.03 / 2018-JAN-25) 14
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All four inputs are protected using voltage resistor dividers together with limiting diodes against voltages
below 0V (GND) and above +3.3V DC. Input circuit of the first two inputs IN_0 and IN_1 is shown below:
+3.3V
IN_0,
IN_1
microcontroller
and stepper
motor driver
10k
10k
1nF
GND
GND GND
Figure 3.7 General purpose inputs IN_0 and IN_1
The two inputs have alternate functions depending on configuration in software. The following functions
are available:
Label
(connector pin)
Default Function
Alternate function 1
Alternate function 2
IN_0 (5)
Digital input
+24V compatible,
internal 20k pull-
down resistor
Step signal input
(connected to stepper motor driver step
input)
+24V compatible, internal 20k pull-down
resistor.
Please note: the bandwidth of the low-pass
RC (10k / 1nF) filter at the input is 16kHz (-
3dB) which will limit the upper step
frequency
Left stop switch
+24V compatible,
internal 20k pull-
down resistor
IN_1 (6)
Digital input
+24V compatible,
internal 20k pull-
down resistor
Direction signal input
(connected to stepper motor driver
direction input)
+24V compatible, internal 20k pull-down
resistor.
Please note: the bandwidth of the low-pass
RC (10k / 1nF) filter at the input is 16kHz (-
3dB)
Right stop switch
+24V compatible,
internal 20k pull-
down resistor
Table 3.3 Multipurpose inputs / alternate functions
All four inputs are connected to the on-board processor and can be used as general purpose digital inputs.
Using the alternate function 1 of IN_0 and IN_1 it is possible to control the on-board stepper motor driver
with the help of an external stepper motor controller using step and direction signals (Please see separate
TMCL firmware manual / axis parameter 254 for more details how to enable this mode). For the step and
direction signals the signal levels are the same as for the general purpose digital inputs. Please note that
the low-pass filter (for noise rejection) at the inputs offers a bandwidth of 16kHz (-3dB).
IN_3 can be used as analog input, also. A 12bit analog to digital converter integrated in the microcontroller
will convert any analog input voltage between 0 and +6.6V to a digital value between 0 and 4095 then.
3.4.1.4 Inputs IN_2, IN_3, Digital Outputs OUT_0, OUT_1
The eight pin connector of the PD28-1-1021 / PD28-3-1021 provides two general purpose outputs. These
two outputs are open-drain outputs and can sink up to 100mA each. Both outputs OUT_0 and OUT_1 share
pins with two of the four inputs (IN_2 resp. IN_3).