I've been trying to construct a serial Arduino from the schematics on arduino.cc on a piece of stripboard. The Atmega8 is already programmed with a bootloader, as confirmed by the flashing of an LED on Atmega8 pin 19, called digital 13 by Arduino. The flashing happens immediately after releasing Reset, and repeatedly every 12-13 seconds.
Here are the pages and the base schematic:
http://www.arduino.cc/en/Main/ArduinoBoardSerial
**broken link removed**
The problem I'm running into is with the serial communication. I am using a self made cable that ends in a keyed 3 pin molex KK connector. I've shorted the RX and TX lines at that KK connector, and Hyperterminal returns the keys I've pressed just peachy. So I feel confident that problem is somewhere on the board.
I'm using the RS232 level shifter described in the schematic I linked to above. After a bunch of troubleshooting and fidgeting, I noticed that the schematic for a level shifter on Sparkfun points out that the electrolytic capacitor should be reversed, with the positive leg going to circuit ground. So, I removed the cap and put it back in 180 degrees. The schematic for the level shifter on the Bill's Firefly board shows the same thing. Now after connecting it up and sending a few characters, the capacitor's positive leg shows a voltage of -6v to -8v compared to circuit ground. Unless someone is going to tell me otherwise, I'm going to have to say this is an error is the Arduino schematic.
https://www.electro-tech-online.com/custompdfs/2007/11/RS232-Shifter-v2.pdf
Thing is, that didn't fix the problem. Still nothing going back and forth. WHen I pop the Atmega out of the socket, and bridge the spots on the socket for RX and TX (atmega pin 2 and 3) I do NOT get anything echoed back to the terminal.
In case it matters, I should also point out that I am using 3904 and 3906 transistors. I couldnt find any of the BC's to use. If this could cause a problem, please let me know.
Im at a loss. The level shifter does have a ton of parts, but it has plenty. My multimeter doesn't have a method of testing inductance, capacitance or transistors. I do have an oscilliscope, but itll take forever to dig out after a recent move.
Help me break down the level shifter into testable parts, so I might figure out what's wrong. I simply don't know enough analog to be able to say 'if I do this here, this should read X'. If you were troubleshooting this on your project, how would you test the pieces to determine where the problem was?
Here are the pages and the base schematic:
http://www.arduino.cc/en/Main/ArduinoBoardSerial
**broken link removed**
The problem I'm running into is with the serial communication. I am using a self made cable that ends in a keyed 3 pin molex KK connector. I've shorted the RX and TX lines at that KK connector, and Hyperterminal returns the keys I've pressed just peachy. So I feel confident that problem is somewhere on the board.
I'm using the RS232 level shifter described in the schematic I linked to above. After a bunch of troubleshooting and fidgeting, I noticed that the schematic for a level shifter on Sparkfun points out that the electrolytic capacitor should be reversed, with the positive leg going to circuit ground. So, I removed the cap and put it back in 180 degrees. The schematic for the level shifter on the Bill's Firefly board shows the same thing. Now after connecting it up and sending a few characters, the capacitor's positive leg shows a voltage of -6v to -8v compared to circuit ground. Unless someone is going to tell me otherwise, I'm going to have to say this is an error is the Arduino schematic.
https://www.electro-tech-online.com/custompdfs/2007/11/RS232-Shifter-v2.pdf
Thing is, that didn't fix the problem. Still nothing going back and forth. WHen I pop the Atmega out of the socket, and bridge the spots on the socket for RX and TX (atmega pin 2 and 3) I do NOT get anything echoed back to the terminal.
In case it matters, I should also point out that I am using 3904 and 3906 transistors. I couldnt find any of the BC's to use. If this could cause a problem, please let me know.
Im at a loss. The level shifter does have a ton of parts, but it has plenty. My multimeter doesn't have a method of testing inductance, capacitance or transistors. I do have an oscilliscope, but itll take forever to dig out after a recent move.
Help me break down the level shifter into testable parts, so I might figure out what's wrong. I simply don't know enough analog to be able to say 'if I do this here, this should read X'. If you were troubleshooting this on your project, how would you test the pieces to determine where the problem was?
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