Questions tagged [uart]

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Minicom: send string when newline is detected

I have 3 different USB-to-UART FTDI cables and use minicom to debug some device. My problem is only one of these cables can buffer characters until I send a newline. Eg when I type the string "...
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Reading /dev/ttyS4 from a BeagleBone running Debian 10 not what is written

I am pulling my hears trying to make ttyS4 up and running on a Beaglebone black. I have set up UART4 in my /boot/uEnv.txt (see it at the bottom of my question). On the Beaglebone I have the comms cape ...
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Trouble finding on-board serial port via UART: "-bash: echo: write error: Input/output error"

I have an old tv box that I wiped recently with Linux. I would like to connect a device to its onboard UART pins, to which I've soldered wires that connect to a UART adapter on my PC. I opened up a ...
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Manually installing drivers on Linux Mint

I am currently trying to install a driver through terminal. It is for the USB UART XR21B1411 serial port adapter. I installed it in the past, but cannot remember how I did it. Here is a link to the ...
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How to write a .read function in serial tty driver with console struct

I am writing a serial tty driver in linux which will be used as a UART driver for the boards console(all operation from login to shutdown). I have written the .write operation of the console which is ...
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UART Console in Linux using Custom TTY Driver works as kernel log console issue

I am currently working on RISCV based processor and have written a UART Driver for console. I have the bootargs given as our custom console and I can now only see the kernel logs and not anything ...
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218 views

Enabling second UART in U-Boot

I am working on a project with SAMA5D3-xplained board with CortexA5 processor and embedded Linux. I would like to send and receive some data via UART during U-Boot is running and before a kernel is ...
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614 views

The linux boot message in dmesg doesn't output to uart

My problem is my linux is success for boot but there is no more boot message output to uart(ttyPS0) after "Starting kernel...". As you can see in the pic, there is a lot of boot message in ...
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140 views

How to redirect GRUB2 output to a MMIO serial UART?

Is it possible to redirect GRUB2 output to a MMIO serial UART? For example I have a UART that is displayed in a Linux boot log as: AMDI0020:01: ttyS5 at MMIO 0xfedca000 (irq = 4, base_baud = 3000000) ...
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How are the TTY and serial_core related?

I need to write a new character device file for the UART, which allows a few more file operations than usually allowed (not just open, write, etc..) I'm on an embedded mainline linux kernel (v 5.4). I ...
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How does the kernel interacts with drivers and device tree?

I have an embedded linux system running on a board. I had, in the device tree, the uart device, and also a driver for that. In that case, after boot, I could see a /dev/ttymxc0 "file" in the ...
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Use rs485 driver specifying the DE pin

On an embedded system (STM32MP1 w/ Yocto environment) I need to control an rs485 transceiver. Unfortunately, the DE pin of the transceiver is connected to a generic GPIO pin of the MPU and not to the ...
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6 votes
1 answer
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How to active the second console to a FreeBSD guest running in bhyve?

Background I'm running FreeBSD 12.1-RELEASE as a host for bhyve virtual machines. I have a FreeBSD 12.1-RELEASE guest running inside a VM. I would like to have two TTY-class devices configured for it. ...
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Samsung SMT-G7401 hack

Samsung SMT-G7401 hack introduction I have an SMT-G7401_PCS01B (Horizon box) from UPC Switzerland and I would like to install debian or multimedia linux distribution on it if is it possible, if is ...
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Bash script - Watch serial-port for specific string, then send back commands

I try to use a bash script to watch the serial-port for a specific string. If this string is shown, some commands should be send back to the connected device. It´s a router I am connected to. It is a ...
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What does PS in ttyPS* stands for?

What does PS in ttyPS* stands for? Where, in general, can I find the expanded names of devices under /dev?
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Raspberry Pi UART not working

I've tried everything. Raspberry Pi 4 echo works. Linux echo works. But when I connect the two UARTs together, no information is sent.
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176 views

Is there a limit to the number of FTDI connections on Debian 9?

I have a Debian 9 box, and if I plug in 1 of my devices, its UART shows up in both lsusb and in the output of ls /sys/bus/usb-serial/devices/. When I attach 2, the 2nd one always shows up. But for ...
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1 vote
1 answer
399 views

Read Write Serial Device not Working in Shell Script

I have a USB serial device connected to my Linux VM (Ubuntu 18.04LTS). It accepts byte streams in certain format and will return some content. To read from the device, I have written the following ...
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170 views

BeagleBone Slackware UART issue

I'm working with a custom made image of Slackware ARM 14.1 with kernel 3.8.X since about 3 years and now needed to upgrade kernel for cdc-acm driver and watchdog. I've tried different kernels from ...
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UART to UART tcp/ip connection

Need to transmit and receive data(TCP/IP) between 2 raspberry through serial tx/rx pins (/ttyAMA0). Best way to do it? Better if this will be done from kernel space. Thanks!
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2 votes
1 answer
2k views

Debian not recognizing my ttyS0 / console redirection not working

I have a fitlet2 (https://fit-iot.com/web/products/fitlet2/) which has a serial port. I can connect to the serial port of the fitlet2 with screen from my computer (screen /dev/ttyUSB0 115200) and ...
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1 vote
1 answer
716 views

Mirroring USB HID signals on Open WRT through UART [closed]

The setup: a Linkit Board (Smart 7688 Duo) running OpenWRT and a generic keyboard connected on the USB host. The goal: dumping the signal we get from the /dev/input/event0 and send it through the ...
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2 votes
1 answer
667 views

Hardware controlled RTS on tty

I have a UART whose RTS pin is connected to an external RS485 transceiver, so that asserting the RTS pin would set the transceiver to send mode. I thought I could configure the serial port to use the ...
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9 votes
2 answers
10k views

Retrieve file over serial without kermit and lrzsz

I have an embedded Linux on a custom board and I would like to send and receive file over its serial port. The only way to communicate with this device is over serial and the device offers a console ...
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1 vote
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Utilizing UART/Serial port driver inside another Linux module/driver

I am implementing a network module/driver in Linux which uses net_devices structure. And so far I have been able to add and remove my module to and from kernel space using insmod command. Via ifconfig ...
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WvDial serial communication not working with uart /dev/ttySAC4, but works with `screen`

I have embedded system based on Samsung Artik 710 board connected to Fibocom G510 cellular modem module via UART (two lines - RX and TX). When I try to communicate with modem using screen - modem ...
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Strange serial port behaviour on Raspberry PI

I'm trying to receive serial data on a Raspberry Pi through the GPIO15(RXD) pin. I have the following python script: serPort = serial.Serial("/dev/ttyAMA0", baudrate=2400) while True: rcv = ord(...
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2 votes
0 answers
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How to Verify that a UART is Enabled on a Beaglebone Black

Question Is the existence of a /dev/ttyO* symlink evidence that the corresponding UART device is enabled? If not, how can I check whether or not the UART has been successfully enabled? Details I'm ...
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3 votes
3 answers
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Failing to Enable UARTs on Beaglebone Black

Short and General Question I'm running Debian 9 (Stretch) on a Beaglebone Black with kernel 4.9. I have tried following the instructions that I've found online, but have thus far been seemingly ...
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3 votes
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How can I determine if a latency is due to a driver or the scheduler?

Using an oscilloscope and toggling some pins I sometimes see latencies of 1-2 seconds from when an 8-byte UART packet is transmitted to when a blocking read returns. The packets are 1 second part with ...
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Display PXE Network Boot Process in VirtualBox Serial Console

I want to start a VirtualBox VM in headless mode and view the network boot process in the terminal via a serial console (e.g. using screen or minicom). How do I accomplish this? Additional context ...
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3 votes
1 answer
2k views

What are the implications of setting the baud rate of a terminal from userspace?

Sometimes I just need to read from a serial device, so I skip the complexities of minicom or screen and just cat. However, this only works if I first set the baud rate of the terminal using stty <...
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4 votes
1 answer
9k views

socat - UART logging and redirecting

I am currently trying to log all communication from and to /dev/ttyUSB0 and simultaneously be able to connect minicom/screen to the same device for interaction. I tried a couple of tools and ...
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6 votes
1 answer
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How to use UART pins on Orange Pi zero?

I want to use UART1 or 2 (see picture) on the Orange Pi zero. But when I try to open the port with screen /dev/ttyS1 Screen terminates. I found here that I needed to add "overlays=sun8i-h3-uart1" in ...
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1 vote
1 answer
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Copying or redirecting text as input to UART, need to enforce slower bandwidth

Basically i'm completely sick of typing lots & lots of text. Obviously want type it in file, push it to UART U-Boot, then modify file, try again. But neither Shift+Ctrl+C over screen ttyUSB0 ...
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AT91SAM9260EK upgraded kernel from 2.6 to 4.4, Serial port not working

Admittedly this is big kernel jump. 2.6 had no concept of device tree and I have not yet created device tree for my product. So just default device tree files with older form of UART settings in board ...
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3 votes
1 answer
2k views

Wireshark: Remote capture over UART

TL;DR: How to pipe properly over UART the output of a remote tcpdump to a local wireshark ? I try to capture packets that flow through an embedded device to which I don't have the ability to install ...
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1 vote
1 answer
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What is the relation between UART and the tty?

When I write programs for my own FPGA, I must select UART to emulate a terminal and for my FPGA design but I don't know exactly what that means. I believe that UART is a basic serial transmission ...
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1 vote
1 answer
48 views

odroidxu4 changing default uart2 to uart0

previously thank you for watching this post. I have tried to run linux on odroidxu4 and of course the logs are written through uart2 (this uart seems default in odroidxu4) But what I'm trying to do ...
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1 answer
590 views

serial DMA pausing after 2048 bytes

I have a sama5d36 device running Debian jessie (kernel 4.1.10) with a DMA USART. To get the DMA USART to output correctly I had to turn off ECHO and ONLCR. stty -F /dev/ttyS2 -echo -onlcr speed ...
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3 votes
2 answers
1k views

Detect what driver is loaded for a UART connected chip?

I'm trying to detect what driver is responsible for providing the HCI interface for the Raspberry Pi 3 Bluetooth module. Here is an equivalent of what I'd like to achieve but for a USB dongle. user@...
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1 vote
0 answers
234 views

Load a Bluetooth driver on top of a generic TTL-232R->USB cable

I have one of these TTL-232R->USB cables which I usually use to access a terminal on an embedded board. They are usually detected like this: [89702.948822] usb 2-3.7: new full-speed USB device number ...
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7 votes
2 answers
871 views

RaspberryPi serial port

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 ...
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4 votes
1 answer
855 views

How to configure embedded kernel to use serial line for PPP instead of TTY

I am about to start working on an embedded system which runs kernel v2.6.x. It is configured to use its serial line as a TTY (accessible via e.g. minicom, stty), but I want to run IP over the serial ...
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1 answer
966 views

Linux USART Serial Port

I'm trying to set up a USART serial port on a custom board with a SAMA5D36 processor, but I am unable to read in data from a connected device. When I run setserial -g /dev/ttyS1 I get the following ...
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4 votes
1 answer
14k views

Kernel parameters "console" and "earlycon" refer to old hardware?

I first found this by investigating parameters for earlycon but found that the options for console look almost identical. Both are present below and were taken from this source: From documentation ...
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