These are the features of the device I wanted to build.

• 8 Channels
• 5 ns time resolution
• TTL output/input level
• Trigger input
• Marker output
• Remote control via USB
• Large capacitive TFT touchscreen
• Should fit in a 13x11x5 cm aluminum enclosure

Mechanical design

The device consists of three parts: The main PCB (130mmx100mm), the 4” TFT display which is mounted on top of it and a small 40mmx100mm PCB for two additional BNC connectors and the IDC connector. The small PCB is connected to the main PCB by a ribbon cable.

All connections are on the left and right side of the device. Two LEDs on the top of the device signal the “wait for trigger” and the “running” state to the user.

The design was meant to fit in an extruded aluminum enclosure I found on AliExpress.

Circuit design

The device is powered with 5V via a barrel jack socket. A DC-DC converter chip converts the 5V to the 3.3V supply for the MCU and the FPGA.

The MCU is a Stm32F446RE microcontroller with an attached CAT24C256 Eeprom for storing persistent data. The MCU and the FPGA, a 10M08SCE144C8G, communicate via Uart.

All outputs and inputs are buffered with 74AHCT14 Schmitt trigger chips and protected by ESD diodes. The output impedance is 50 Ohm.

The device can be remote controlled via its USB-B connector. The schematics can be found on the download page.

PCBs

The main PCB is a standard 4 layer board, the smaller satellite PCB is with two layers. I had the boards manufactured and soldered the parts myself.

Firmware

The eight channels can be configured independently. Each channel can be set as periodic and inverted. The channel modes are

• Clock (always periodic) with parameters
  Frequency
  Duty cycle
  Phase

• Pulse with parameters
  Delay
  Pulse
  Pause

• Double Pulse with parameters
  Delay
  Pulse1, Pause1
  Pulse2, Pause2

• Uart with parameters
  Baud rate
  String
  Data Bits
  Stop Bits
  Parity

• Bitstream with parameters
  Bit duration
  Binary String

• Pulse Train with parameters
  List of pulse/pause times

• Number with parameters
  Bit duration
  Value
  Bits
  LSB first

• PWM with parameters
  Frequency
  Phase0
  

Trigger sources:

• Auto
• Bus
• External
• External Gate
• User(GUI)

Device Limits

Max. 10000 transitions
Pulse width between 15ns and 10s
Frequencies between 1Hz and 65MHz
PLL clock variation between 120MHz and 260MHz

Remote Control Interface

The device can be remote controlled via its USB interface. To a host it is visible as a composite USB device with a USBTMC interface and a CDC (serial) interface. The language used is SCPI.

Example:

Set the clock frequency of channel 3 to 4MHz:
CHANnel3:CLOCk:FREQuency 4MHz

Read back value:
CHANnel3:CLOCk:FREQuency?
→ returns 4000000.000000

This is a list of selected commands. To get the full list use command „SYSTem:HELP:HEADers?“.