M-20
RJ9 pinout
All units are connected to the main box by RJ9 connectors. Pinout of the external unit connector is described in following table.
| Pin number | Wire color | Pin functinality |
|---|---|---|
| 1 | Red | Supply (+12V) |
| 2 | Black | Ground |
| 3 | Yellow | Alert output. Alert is activated ater reception of 5 lidar pulses and stays active 5 second after reception of the last pulse. It is connected to the LED and beeper in the central unit. Level CMOS 5V. |
| 4 | Blue | This pin is bidirectional. It is an output of the receiver and also input to the microcontroller. Connecting pin 5 of all external units allows to synchronise the generated responses. However, this connection is not used in the central unit. Level CMOS 5V. |
Central unit connects all pins (except pin 4) together. This allows easily extend the number of external units.
Programming connector pinout
When the front conver of the external unit is removed then there is an access to the programming connector (to remove the cover the screwdriver TORX size 10 is necessary). This connector is connected directly to the microcontroller.
| Pin functionality | Pin functionality during programming | Standard pin funtionality |
|---|---|---|
| 1 | MISO | RX (as pin 4 at RJ9) |
| 2 | SCK | Alert (as pin 3 at RJ9) |
| 3 | Reset | - |
| 4 | MOSI | TX - pulse otput |
Internal picture of external unit
Note - the components were slightly damaged when glue was being removed.
Lower left corner shows 3 receiving IR photodiodes. Signal then goes to the wideband amplifier followed by fast comparator. Signal is then processed in the digital part (located in the middle and right half of the picture).
Digital part consists of chip HC04 which generates clock 10MHz and it also interfaces microcontroller to the receivers and transmitters chips. Signal processing is made in mictrocontroller ATTiny45
Transmitter circuit (shown on the bottom) contains 3 MOS drivers which control 8 IR LED.
Power supply provides 5V for the digital part and 12V for receiver and transmitter.
Author of these pages takes NO RESPONSIBILITY of any damages nor expenses caused by supplied informations.