Hi,
I have an Appa 207 multimeter which outputs its measurements via a RS-232 phototronics serial port at the back, according to the manual. I do not have the RS-232 to USB cable for this multimeter so I was trying to find some way to make it work. According to the manual, the transmission via RS232 is one-way (multimeter to PC only). I disassemble the unit and found 2 LED inside this phototronics serial port. By setting the multimeter to transmit its data and probing at the TX pin on the board I can see some sort of serial data stream on my oscilloscope. However, they are clearly not pure RS232 to me, more likely some customized waveforms to light up the LED.
I tried to use the TFMS5400 40kHz infrared receiver to see if it's infrared but nothing is received. I also tried with a cheap cellphone camera to see if the LEDs light up during transmission but they also don't light up in the viewfinder. Maybe they are not infrared LED.
Any ideas how I could receive the data from this port? I can possibly trace it back to the processor board where the RS232 signal is originally generated and extract it from there but maybe there is an easier way.
Attached are the photos of the 2 LED and the waveform.
I have an Appa 207 multimeter which outputs its measurements via a RS-232 phototronics serial port at the back, according to the manual. I do not have the RS-232 to USB cable for this multimeter so I was trying to find some way to make it work. According to the manual, the transmission via RS232 is one-way (multimeter to PC only). I disassemble the unit and found 2 LED inside this phototronics serial port. By setting the multimeter to transmit its data and probing at the TX pin on the board I can see some sort of serial data stream on my oscilloscope. However, they are clearly not pure RS232 to me, more likely some customized waveforms to light up the LED.
I tried to use the TFMS5400 40kHz infrared receiver to see if it's infrared but nothing is received. I also tried with a cheap cellphone camera to see if the LEDs light up during transmission but they also don't light up in the viewfinder. Maybe they are not infrared LED.
Any ideas how I could receive the data from this port? I can possibly trace it back to the processor board where the RS232 signal is originally generated and extract it from there but maybe there is an easier way.
Attached are the photos of the 2 LED and the waveform.
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