Generic Speedlite Hack for Canon EOS SL3 / 1500D

Background:

Canon has removed the central universal hotshoe pin from some of newer models, most third party flashes no longer work.

Here was the dirty hack on my third party flash Viltrox JY610C, to let it works with the EOS 1500D.

Analysis:

Sniff the signals between speedlite and older Canon cameras EOS 450D, noticed that when C2F at logic HIGH, the flash is fired after hold CLK line at logic LOW for 4ms.

Concept:

The key concept of this hack is monitor the C2F and CLK lines with a low pin count microcontroller, then trigger the flash at right timing.

Tools:
1. Screw driver

2. Soldering Iron

3. PICKit or equivalent

Steps and Procedure:

1. Remove batteries from speedlite.

2. Unscrew and open the cover of speedlite (CAUTION: High Voltage! Even without batteries!)

3. Discharge the big capacitor.

4. Solder 4 wires CLK, C2F, TRG and GND from the hotshoe PCB in speedlite.

5. Solder a wire from 3V on the speedlite batteries compartment.

6. Put all parts together as illustrated in the schematic, parts list as below:

• a. Microcontroller, Microchip PIC12F675
• b. Small signal transistor, IRLML2502 or equivalent.
• c. Resistors, 2k2 x 1
• d. Capacitor 0.1uF x1
• e. Doughnut board

7. Program the binary attached into PIC12F675 with PICKit or equivalent before solder into the PCB (please note that the schematic attached does't support In-Circuit Programming).

8. Attached the PCB to speedlite.

9. Keep the circuit neatly within the speedlite compartment.

10. Now the speedlite manages to fire correctly when mounted on newer Canon EOS, at least with my EOS 1500D.

How to test:

1. Mount the modified speedlite to the camera.

2. Point and snap a photo of mirror or reflective surface.

3. The speedlite in the photo is bright indicated it has fired at the right timing.

Limitation:

1. Special function on the speedlite for example multiple trigger and rear curtain sync may no longer work.