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Author Topic: Not able to program my breadboard arduino serial  (Read 1344 times)
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computer not detecting my breadboard arduino connected through serial port (RS232 DB9 port)

the circuit connection can be seen in the picture
basically it is atmega168 rx,tx -> MAX232 -> DB9 female (pin 5 of db9 is grounded)

i have also connected a 1k ohm resistor between rx,tx and max232 (but it is not shown in the picture)

the chip i am using is ATMEGA168A-pu which has been bootloaded by my UNO (using optiloader)
i am sure the chip was bootloaded correctly as LED on pin13 blinks everytime i press reset

after making connections i connect the RS232 cable to my comp serial port but my comp does not recognize any external hardware!!
what should i do??

also there is not driver installation for arduino serial in the arduino folder (only the ones for the USB arduinos)

what should i do?
any help would be appreciated smiley


* DSC01684.jpg (313.93 KB, 794x1123 - viewed 28 times.)
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Top suggestion: Get an USB adapter. They are quite cheap. Should save you tons of time if you get one with auto-reset capability (RTS/DTR).

If you use the built-in RS232 ports of your mainboard and they are enabled in the BIOS,there is nothing to be 'magically' recognized. Any recent OS supports those right away. There will also be NO "new hardware found" event for anything connected to them. The way you have it wired up now, there is also NO auto-reset. This will make uploading code quite tedious, maybe even close to impossible.

The absolute minimum for hassle-free upload is:

RX, TX, RTS (or DTR), GND.
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Top suggestion: Get an USB adapter. They are quite cheap. Should save you tons of time if you get one with auto-reset capability (RTS/DTR).

If you use the built-in RS232 ports of your mainboard and they are enabled in the BIOS,there is nothing to be 'magically' recognized. Any recent OS supports those right away. There will also be NO "new hardware found" event for anything connected to them. The way you have it wired up now, there is also NO auto-reset. This will make uploading code quite tedious, maybe even close to impossible.

The absolute minimum for hassle-free upload is:

RX, TX, RTS (or DTR), GND.


thanks so much for your suggestion! it help me a lot

turns out my bios settings for serial port were disabled
now my arduino IDE shows ttys0 in the tool>serial port(serial port in linux) smiley))))))

but there still there is a bug

when i select 'arduino diecimila or duemilanove w/atmega168' in tools>board and try to upload blink
it gives the following error :

avrdude: stk500_recv(): programmer is not responding

also my auto reset is working fine because i see the LED blinking when i connect the serial cable.

what could be the problem?
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It is physically impossible for auto-reset to work with only RX/TX wires. Auto-reset needs RTS or DTR to work.

The LED initially blinks... only because you give power to the chip.
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It is physically impossible for auto-reset to work with only RX/TX wires. Auto-reset needs RTS or DTR to work.

The LED initially blinks... only because you give power to the chip.

err sorry i forgot to mention that i added the auto reset (a 100nF->max232->DTR)
now it blinks everytime i press 'upload'

but it is giving the same error again and again and not able to upload

i also tried removing the 1k resistor between Tx and MAX232 but it still gives the same error..
is there something wrong with the bootloading?? (since i used optiloader to do it)

but then if the bootloader was screwed then there is no way the LED would blink on reset??

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How about a schematic? Can't tell from that picture if you have the MAX232 wired up correctly.
If you put a multimeter on MAX232 pins in use do you see the DB9 pins sitting at -10V or so, and the uC side sitting at 5V, when no transfers are happening?
You have the polarized caps oriented correctly also?

If that all checks out, press & hold the reset while you start the IDE, release it when it says "compiled xxx of xxx bytes", something like that.
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How about a schematic? Can't tell from that picture if you have the MAX232 wired up correctly.
If you put a multimeter on MAX232 pins in use do you see the DB9 pins sitting at -10V or so, and the uC side sitting at 5V, when no transfers are happening?
You have the polarized caps oriented correctly also?

If that all checks out, press & hold the reset while you start the IDE, release it when it says "compiled xxx of xxx bytes", something like that.

here is the schematic (the only difference being MAX232 instead of max3232 and 1uF caps instead of 100n (polarities have been double checked)

tx pin giving 0V
rx 5v

db9 pins 2,3,4 are giving -10 volts

how can db9 pin have -10 volts when tx is 0V ??????????????????
shoulnt it be +10 volts??????


* freeduino_serial_v2_schematics_L.jpg (120.48 KB, 713x417 - viewed 32 times.)
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then i am not uploading anything-

voltage across TX and ground (or T1in) = 0v (actually it was around -0.02) how can it be nagative?
voltage across T1out = -10 volts

is this even possible?

isnt the MAX232 supposed to change levels from 0v to +10 volts? (and not to -10v as in my case)
i am confused
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and i also double checked the polarity of the multimeter and nothing wrong with that
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