There is no marking on the transmitter… It is a 5V device, I measured the voltage before I removed it from the PCB. And I connected it to 5V on GPIO connector.
I didn’t check, maybe the led was fried before (it comes from an old satellite demodulator I found in a waste disposal site).
Did you used resistor on signal line?
Yes, I used a 100 Ohm, and also tried without one.
To buy a new one, I recommend to search for “TOTX” devices.
Assuming wiring is OK, it’s likely you got a Transmitter with CMOS input, like TOTX1952A, which need >3,5V as High. The GPIOA from N2 is 3V3 TTL output. So you need a Transmitter with TTL input, like TOTX173 or TOTX177.
For all Transmitters supplied by 5V, I recommend 470R or 1K Series-R for the input signal, to limit the clamp current when 5V is switched off.
Or just use a 3V3 Transmitter like TOTX1701A, which even doesn’t need the Series-R.
I see… When connected to Vcc/Gnd, should the transmitter have its led turned on? Just to check if it is a level input issue, or a fried device…
As I don’t have any spare toslink connector, right now¹, how could I buffer the GPIO output so I can connect it to S/PDIF input? I may have some op amplifiers laying around…
¹ TOTX are not easy to find… I plan to buy this one: https://fr.farnell.com/cliff-electronic-components/fcr684208t/conn-tx-optique-90-male-pcb/dp/2991613 Is it OK ? Should I use a current limit resistor?
When you connect the input pin to VCC (5V), LED should be on.
This should be fine, has TTL input. It’s also a wide-range supply device, you can supply by 3V3 or 5V.
Regarding Series-R, it depends on the supply voltage you will use. For 5V I recommend to use one, for 3V3 it’s not mandatory.
Ok, thanks!
This topic was automatically closed 91 days after the last reply. New replies are no longer allowed.