![]() ![]() The signal level is relative to the common ground. RS-232 is also an “unbalanced protocol.” It uses a single conductor for each signal and a common ground. To make this happen correctly, the data rate, hand-shaking, start and stop bits, and error checking must all be pre-defined. This implies that the data word is transmitted as single bits to the receiver, which puts the word back together. A voltage of +12 Volts (usually +3 to +10 Volts) represents a binary 0 and -12 Volts (-3 to -10 Volts) is a binary 1.Īlso, RS-232 is an “asynchronous serial protocol”. This means that a single electrical signal is compared to a common signal (Ground) to determine binary logic states. Voltage levels are defined as a range from -12 to +12 Volts. It is possible to operate at rather high data rates if the distance is short. The absolute maximum data rate is difficult to determine due the differences in the transmission line and cable length. RS-232 is capable of operating at data rates up to 20 Kbps and can transmit data about 15 meters (50 ft). The physical characteristics of the hardware include both a 25-pin and 9-pin D sub connector. ![]() The “EIA” stands for “Electronic Industries Association” and the “RS” stands for “Recommended Standard.” That being the case, it was always rather loose. What Is It?Īt one time, RS-232 / EIA-232 was the most widely used communication standard on the planet. In this paper, we hope to dispel some of the mystery and give you the essentials of RS-232. To them that funny looking 9-pin connector that we old folks cut our teeth on is a mystery full of uncertainty and doubt – with a little bit of fear mixed in for good measure. Rather, they were brought up on broadband and Wi-Fi. It’s just odd to me that it works so nicely, like no garbage characters or odd delays at all with this set up.There is an entire generation of technicians in the work force today that did not grow up in the days of the TRS- 80 and Commodore 64 PC. And yeah, these were kind of the cheapo version off amazon so you never know. I traced the lines and all seems okay, but to be fair I’m not completely sure what I’m looking for or if I traced the lines correctly. Funky, right?Īlso, can you elaborate on the echoing and how it relates to this scenario? The 0.13V is the voltage coming out of the TX pin on the RS232 board, and that is within the photons “readable” range, Hello! I think I agree with you that it may just be my board doing some odd stuff. But, interestingly, both ways work if you put a connecting line between the transmit and receive lines to my sensor. However, I have tried both set-ups, with my yellow line connected to pin 3 and with yellow to pin 2 and neither work. If the wires were crossed it wouldn’t work but then if you solder the wires together, because the photon isn’t transmitting data, you are essentially “uncrossing” the wires so the data gets to the correct pin. Hello I think I understand what you are saying and that was my first though as well. Let me know if you all have any more suggestions! I will try checking voltages today and getting some cleaner solders going. My bad ScruffR, took me a while to get my head wrapped around this one.īut this still doesn’t give me the correct (or any) results. But then if I need data to be streaming into my female pin 3 for the shifter to work, I would have to cross the wires as suggested. So thinking about it now, if this set up (for bypassing the shifter) works then data is streaming into pin 2 on the female end as outgoing data and being received on pin 2 on the male end (as it is supposed to, right?). ![]() Essentially for that test I was just creating a female rs232 end to my wire. Because the wire is open ended, I wanted to just use the female RS232 end of the board as a means to create a direct connection from the sensor to my computer, just to ensure that the senor is streaming data correctly and to see what format it is coming out as. So the interesting part is that if I cross my serial input and serial output lines, it works with a few quirks here and there (found this out by accident haha)Īnd you are correct that I am bypassing the shifter on the board when I am using it to send data to putty. Index = 0 // Index into array where to store the character This is my code, it is simple, just publish the data when it receives 48 characters: char incomingByte = 0 // for incoming serial dataĬhar inData // Allocate some space for the stringĬhar inChar // Where to store the character read incoming byte However, when I attach my photon, I get no response at all. ![]()
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