LIghtCrafter Flexible Trigger Configurations

Hi Pedro, I need some help interfacing a 5V MCU with the LghtCrafter Trigger inputs.

I would like to know if there is a simpler way of doing it, without modifying the system board.

I couldn´t find the R282 0ohm resistor. Where is it?

Thanks

Enio,

Unless you have a level shifter on the MCU to change the 5V signals to 3.3V, you will have to modify the board. 

R282 is in the back of the SyStem Board (top board). It is in the group of three resistors that has a label next to the daughter card connector. It is between the daughtercard connector and screw hole, next to a ground test point.  R282 is the middle resistor. 

See the bottom left corner of this photo:

Pedro, I have a few quiestions about the trigger signals:

1. Which is the treshold voltage for 3.3V and for 5V?
2. Can I power a circuit from the EXT_TRIG_VCC pin, how much current can I source

Enio,

The threshold voltage for TRIG_IN_CON is handled by the TXS0101. From its data sheet, the Vil is 0.15V and Vih is Vcc - 0.2V where Vcc is the EXT_TRIG_VCC. Vcc can be anywhere between 2.3V to 5.5V.

You can power a circuit from EXT_TRIG_VCC. The amount of power is dependent on how much is consumed on the LightCrafter and the supply that is sourcing it. For instance, EXT_TRIG_VCC supports, 1.8V, 3.3V, and 5V options.

• On default configuration of LightCrafter, the 5V supply is sourced from USB VBUS. So there is very little 5V current consumed in the system and the budget is dependent on what the USB port provides. On this supply, there is a TPS60150 (U25 in system board), but it is disabled and the P5P0V supply is disconnected from SYSPWR (the LightCrafter power input).
• The 3.3V supply is sourced from the driver board TPS63020 (U15 in driver board) that has a max output current of 3A. However, this supply is used for most of the LightCrafter devices. So a significant budget is consumed, but it is not the majority of this supply. To provide an example when LightCrafter is operating at the 20 lumen value (LED set to 274), the overall current consumed at SYSPWR is about 700mA. This includes all the supplies including the LED drivers that use 600mA.
• The 1.8V supply is sourced by the TPS650531 (U15 in system board) has a max rating of 1A.  This supply is shared with some DM365 analog and DDR2 I/Os, as well as, the DDR2 RAM so a few 100mA's are consumed when the DM365's external RAM is heavily used. 

Note that the overall power budget is limited by the power supply into the LightCrafter system. This typically ranges between 2-3A. As you can see, there is enough current available on these supplies to power at least 100mA external circuit.

Thank you for the response Pedro.

I have a few more questions:

1. I'll be powering a circuit with 3.3 V, to do that I have to solder  0 ohm resistance R285 or R295 (please correct me if I'm wrong). Are these also located in the back of the System Board?
2. Is there any conection to the 3.3V power source of the lightcrafter, that does not require a modification to the board.?
3. Do you have the digikey part number for this 0 ohm resistors?

Hi Enio,

You will have to install 0 ohm resistor at  R295,  which is on the top of system board (above the J7 connector).

Here is the part number for 0 ohm resistor we used:

Digi-Key part number: P0.0AGCT-ND , Manufacture part number: ERJ-1GE0R00C

Could you please tell me how much current would the external circuit consume?

Please be aware of the current you can source from this pin. (Refer to Pedro's post above).

Regards,

Divya

How would I be able to achieve a flexible output trigger configuration?

Industrial cameras currently use triggers of different voltage (e.g. Point Grey Flea 3V and IDS Imaging uEye 5V).

My idea would be to either move the zero-ohm resistor from R292 to R295, and source the appropriate trigger voltage from the camera itself, as most cameras provide some current at the right voltage.

The alternative would be a three position microswitch installed over R291, R292 and R293. Does anyone have experience with this and can you recommend a part that could be soldered directly onto these positions?

As most newer cameras use opto-isolated trigger ports, I wonder if one of these solutions offer an advantage in terms of current to drive the opto-isolated circuit? Also in the application note for "Imaging Source Cameras", it is suggested to output the trigger on pins 1 and 3, which reverses polarity. Does this mean more current?

Regards,

Jakob Wilm

Technical University of Denmark

Hi Jacob,

We have tested the scenario mentioned in white paper i.e, externally triggering the LightCrafter by installing 0 ohm resistors at R292 and R295. But if your camera is capable of sourcing appropriate trigger voltage and current, you can apply idea 1 (U23 is an open-drain level shifter)

Unfortunately, I am not aware of a three position switch. LightCrafter E2E community might be able to help you.

Regards,

Divya