I've just recycled an LCF-23T CMOS camera (http://www.thaieasyelec.net/index.php/Sensors/Light-/-Imaging/4dsystem-JPEG-Color-Camera-UART-TTL-Interface-OV528-Chip/p_177.html) that the vendor describes as TTL-level UART camera. I don't know the original implementation, the mainboard it was connected to was missing.
My camera looks exactly like one from the link above, but because it has an MAX3232 (TSSOP-16) installed (bottom-right corner) I started wondering if the terminals are still TTL-level or maybe RS232-level?
There is a second model, that looks exaclty the same: http://lianchao.sell.everychina.com/p-90650675/showimage.html but doesn't have the MAX3232 installed yet still described as TTL-level. Something is wrong then.
I checked the terminals connections on my model and they are following (looking from left to right): Vcc, GND, TX and RX. TX and RX are connected to MAX3232's T2OUT and R2IN respectively so I'd say they are RS232-level.
In that case (provided the PCB is the same for 1st and 2nd model) how is that possible that without populating the MAX3232 the interface is TTL-level? I'd expect some of the terminals were connected to RxOUT and TxIN but they are not.
How can I check the signal levels with only multimeter and not damaging the camera?
If I connect it to RS232 and it is TTL-level it will be damaged, if connected to TTL-level device and it's RS232 it can damage the TTL device or at least won't work.
Best Answer
The uCAM came in two different versions (it's now obsolete and superseded by the uCAM-II) - a TTL version and an RS-232 version.
From the datasheet:
It looks like you have the RS-232 version.