Hi,
I'm using a easyPIC fusion v7 dev board with an RS232 2 click attachment to talk with a battery charger. I am able to control certain features (output percentage ect.) on a battery charger using HyperTerminal and a serial cable, but when I send the same command through my dev board the charger does not react. I used a logic analyzer to look at the signal coming from HyperTerminal and the signal coming from the Tx line out of the RS232 2 click. The signals are identical (same high/low duration, same number of characters...) except for the voltage. The HyperTerminal voltage is -10V for "low" and +10V for "high" while my click puts out the same signal but at -6V for "low" and +6V for "high".
If I connect the serial cable from the RS232 2 click to my laptop then HyperTerminal correctly sees the command that I want to send. It's just the charger that doesn't react like it should and the only difference I can see is the voltage level.
I looked at the datasheet for both the RS232 2 click and the MAX3237E (the IC on the click) and they state that I should be seeing +/-13V, not +/-6V.
What am I doing wrong? Thank you very much.
Click RS232 2 voltage levels too low
Re: Click RS232 2 voltage levels too low
You are reading the datasheet incorrectly.
The "DRIVER SECTION ELECTRICAL CHARACTERISTICS(1)" table first two parameters state minimum output voltages as +5V and -5V, typical +5.4V and -5.4V
Anything between +3V and +15V or between -3V and -15V are valid RS232 levels.
Older equipment (say 1980's) would typically give out +12V and -12V, but such levels are rare these days for newer equipment. My guess is that your battery charger is older equipment that wrongly depends on higher voltages, or maybe a "naughty" device that powers itself from the RS232 cable.
Only a guess though... exactly what battery charger is it?
.... another possibility is that your battery charger depends on the signals other than just Tx and Rx. Have you checked that DSR, DTR, DCD RTS and CTS signals match between Hyperterm connection and RS232-2 click connection?
.... another possibility is a wiring mistake. Presumably you have used a null-modem cable for RS232-2 click and a straight through cable for Hyperterm?
The "DRIVER SECTION ELECTRICAL CHARACTERISTICS(1)" table first two parameters state minimum output voltages as +5V and -5V, typical +5.4V and -5.4V
Anything between +3V and +15V or between -3V and -15V are valid RS232 levels.
Older equipment (say 1980's) would typically give out +12V and -12V, but such levels are rare these days for newer equipment. My guess is that your battery charger is older equipment that wrongly depends on higher voltages, or maybe a "naughty" device that powers itself from the RS232 cable.
Only a guess though... exactly what battery charger is it?
.... another possibility is that your battery charger depends on the signals other than just Tx and Rx. Have you checked that DSR, DTR, DCD RTS and CTS signals match between Hyperterm connection and RS232-2 click connection?
.... another possibility is a wiring mistake. Presumably you have used a null-modem cable for RS232-2 click and a straight through cable for Hyperterm?
Start every day with a smile...... (get it over with) 
Re: Click RS232 2 voltage levels too low
... Oh.....
.... and welcome to the forum, and to the world of mikroE
.... and welcome to the forum, and to the world of mikroE
Start every day with a smile...... (get it over with)
-
ThugsBunny
- Posts: 2
- Joined: 17 Dec 2019 04:23
Re: Click RS232 2 voltage levels too low
Yep, the Rx and Tx lines needed to be switched. So I think that was the null modem cable thing you mentioned.
Thank you very much for your help!
Thank you very much for your help!
