Jan 6, 2015 - We'll be exploring the Linux command line using the Raspberry Pi as a. Of free software for Mac, Linux, and Windows like PuTTY, minicom,.
![Raspberry Raspberry](/uploads/1/2/4/8/124806100/178176905.jpg)
![Raspberry Raspberry](/uploads/1/2/4/8/124806100/741432892.jpg)
However I am struggling to get the Serial to work with my old B+ and the newest Jessie OS (20170111 or so).
What I did until now:
- read almost every tutorial on the net about it, but most are for wheezy.
- edited cmdline.txt to remove the login console ('console=ttyAMA0,115200 ') and rebooted
- disabled the serial port via raspi-config (results in a disappearing of ttyAMA0)
- messed with config.txt (enable_uart=1), ttyAMA0 reappeared but is still not interfaceable with minicom
- tried to kill the login service, but for me there is no [email protected] somewhere
What I did to test:
connect TxD to RxD and tried to open /dev/ttyAMA0 on minicom with a baudrate of 9600 and try to see if the text I am sending is echoed back.What did I miss or what do I have to do from a fresh Jessie to get ttyAMA0 free?
Sincerely,
Julian
I have a Display that I want to write to. This is possible over the serial port. When I use a USB to RS-232 Converter, that thing works like a charm. I even tried using only the RX, TX and GND wires of the serial converter, and it still works. Now I want to use this Display in a small case paired with a Raspberry Pi, so i don't have any space left for the big USB-RS-232 converter.I have tried using the internal serial port of the Raspberry. It is set to 9600 baud using
$ sudo stty -F /dev/ttyAMA0 9600
. But when I connect it to the display, it only shows up garbage and normal control-commands (that were working using the RS-232 converter) don't work either.Using $ sudo minicom -b 9600 -o -D /dev/ttyAMA0
and looping the GPIOs TX to RX, it shows up the right characters in the minicom
console.Now looping the GPIO-Serial-Port to the USB-RS-232 Converter's RX and TX pins and connecting ground and opening both ports in minicom
with baud set to 9600, only sometimes shows some output on the other terminal, but when it shows any output, it is also just garbage.Jeff Schaller♦
jukisujukisu
2 Answers
I'm quite confident the problem is that the Pi does not have an RS232 interface, while the display has.
The Pi has an (LV-)UART interface, its TX-pin outputs 0V for a logical
0
and 3.3V for a logical 1
. This is quite easy to implement, since 3.3V is already available on the Pi. But this only works for communications on a single PCB or within a single device.For communication between devices over longer distances, a system less prone to interfering signals like RS232 is used. While the logical structure of the waveform (bitrate, timing, start-, stop-, parity- and, though there are other interfaces like I²C and SPI, which are a type of serial interface, but never considered to be 'the' serial interface.
swebersweber
The built-in Raspberry Pi serial port uses voltage levels of 0 to 3.3 Volt, as described here. The USB to serial converter and your display will use RS232 voltage levels of nominally -15V to +15V, with a minimum of -3V/+3V. You need to convert between these two levels.
The port will work when looped back as the output and input voltages are compatible.
meuhmeuh