18 votes
Accepted

Where are the uarts on the raspberry pi 4?

The preliminary Pi4 datasheet shows there are 6 UARTs. UART GPIO 0 14/15 1 14/15 2 0/1 3 4/5 4 8/9 5 12/13 Given that UART 0/1 are both connected to the same GPIO you can only use ...
joan's user avatar
  • 71.1k
13 votes

Pi 4 I/O interface options... and where to find them

The preliminary Raspberry Pi 4 Model B datasheet, section "5.1.1 GPIO Pin Assignments" says: As well as being able to be used as straightforward software controlled input and output (with ...
Ghanima's user avatar
  • 15.9k
12 votes

Where are the uarts on the raspberry pi 4?

As Joan has stated only 1 of UART0/1 is accessible (UART0 /dev/ttyAMA0 is connected to Bluetooth on later model Pi). There are additional UART on the Pi4. Raspberry Pi4 UART is a more up to date ...
Milliways's user avatar
  • 60k
11 votes
Accepted

Bit waveform clarification

To me it looks like ser.write(1) has an implicit conversion to string. So your 1 becomes a "1" which is 00110001, which perfectly fits into your observation.
kwasmich's user avatar
  • 2,702
8 votes

How to get more than one uart interface

The Raspberry Pi 4 supports up to 4 UART interfaces now that need to be enabled by means of an device tree overlay. You can find how to do this and which Pins are used here for now: https://www....
vanthome's user avatar
  • 181
7 votes
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multiple UARTs on the 40-pin

so where was one big misunderstandings. thanks to @joan for pointing to the docs and @tlfong01 for their link to their article: https://penzu.com/public/b94e6b30 essentially, on the raspberry 4, there ...
rmalchow's user avatar
  • 191
6 votes

How to connect SIM800 GSM ADD-ON to RaspberryPi 3

Assuming you are talking about one of these that looks like this you should go over this to test your device. From what I can see This device communicates over serial port (USART) using board pins ...
Shreyas Murali's user avatar
5 votes

How to connect SIM800 GSM ADD-ON to RaspberryPi 3

I was having trouble making my SIM800 hat work with my Raspberry Pi Zero W; I thought it could be because of burnt gpios... So I tried with my Raspberry Pi 3. Same trouble. I then found this solution ...
Rubens's user avatar
  • 51
5 votes

Is Fingerprint Scanner TTL (GT-511C3) compatible with Raspberry Pi Zero?

This Fingerprint Scanner is compatible with the Raspberry Pi Zero. As it uses UART to interface. Amazon.com says the fingerprint scanner uses, "Simple UART protocol (Default 9600 baud)". Since the ...
akasoggybunz's user avatar
5 votes
Accepted

Impact of using UART

The three options are: default configuration UART0/ttyAMA0 to Bluetooth Mini-UART/dev/ttyS0 to GPIOs 14 and 15 pi3-disable-bt no Bluetooth support UART0/ttyAMA0 to GPIOs 14 and 15 pi3-miniuart-bt ...
Janka's user avatar
  • 1,718
5 votes
Accepted

software solution for non-blocking UART communications

This is not correct. Even single core CPUs are capable of running multiple processes giving them short time window to run and then switching to next process. Also both Python and C programs are ...
Mariusz Zieliński's user avatar
5 votes

How do I use a Raspberry Pi to install OpenWrt firmware on a BT HomeHub 5a or PlusNet Hub One router

Note I am deliberately answering my own question There are lots of detailed guides out there; this is an overview of the key points particularly with respect to using a Raspberry Pi as the host. Take ...
nickcrabtree's user avatar
4 votes
Accepted

What is the difference between the GPIO pins BCM 14 and BCM 18?

All of the GPIO pins can be configured for different purposes. At their simplest they can all act as general purpose input/output (hence the name). This means they can be set to act as an outputs, ...
Michael Daffin's user avatar
4 votes

What is the difference between the GPIO pins BCM 14 and BCM 18?

All GPIO pins can be either Input or Output, and many can have alternate functions. See Pinout for details of alternatives. Depending on the Pi model, Pins 8/10 (BCM 14/15) are usually configured as ...
Milliways's user avatar
  • 60k
4 votes
Accepted

How tp get USB to USB UART console without linux

Let me try to un-confuse you :) In the good old days, computers came with serial ports. The standard is known as RS232. These slowly disappeared, first from laptops and then from desktops. These days,...
JayEye's user avatar
  • 1,898
4 votes

Connect sim800 to Raspberry PI (RX, TX)

The circuit as shown will not work as there is no common voltage reference between the SIM and the Pi. You need to connect a Pi ground to either the SIM ground or to the battery ground (-ve terminal)....
joan's user avatar
  • 71.1k
4 votes

Connect sim800 to Raspberry PI (RX, TX)

Just yesterday I managed to make my assembly respond. Here are my steps: Disable Serial Console sudo raspi-config --> Interfaces --> Serial --> No to 1st prompt; Yes for the 2nd Use "serial0" instead ...
Manu's user avatar
  • 41
4 votes
Accepted

Read & Write on UART don't work

Isn't /dev/ttyAMA0 used for Bluetooth on the Raspberry Pi3? You may need to use /dev/ttyS0 or /dev/serial1 on the Pi3 (check in /boot/overlays/README).
joan's user avatar
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4 votes
Accepted

Can I use the TX/RX pins and the USB ports for multiple serial devices?

You can use multiple USB serial dongles. They will appear as /dev/ttyUSBx where x will be a small number such as 0, 1, 2. You can use any serial software you want. They will all use the Linux ...
joan's user avatar
  • 71.1k
4 votes

Disable UART such that it will not be on during the boot process, but only after

You can solve this by setting the bootdelay of u-boot to -2 using the u-boot console: setenv bootdelay=-2 saveenv Another solution is adding these lines of code to include/configs/rpi.h: #define ...
Marcel Bochtler's user avatar
4 votes
Accepted

UART RX stops reading data after working correctly

Check if you have disabled the login prompt on /dev/serial0. What you see may be due to two processes (your script and getty) reading from the same port. Login prompt on serial port can be disabled ...
Dmitry Grigoryev's user avatar
4 votes

Impact of using UART

(See Janka's answer for the practical implications, I just wanted to clear up another aspect of the question). so it's just a software connection. Not exactly. The BCM283x SoCs like many higher ...
Peter Green's user avatar
  • 6,486
4 votes
Accepted

Multiple Rpi Serial Ports Problem

Since I cannot leave a comment, I will use the Answer form. I had a similar task and looked at several multi-port ICs to build onto a board, I ended up using a USB hub and multiple USB to serial (RX &...
Wendall's user avatar
  • 221
4 votes
Accepted

How can I disable the serial console on distributions that use U-Boot?

Here is the video where it is explained step by step how to prevent U-boot console from interrupting autoboot and sending debug messages on UART. I know links only answers are frowned upon, so here' s ...
Dmitry Maslov's user avatar
4 votes
Accepted

Does a UART connection require shared ground?

Q: "Does a UART connection need/require a shared ground?" A: No, it does not. UART is a communication protocol that has been successfully used in applications that prohibit the use of a ...
Seamus's user avatar
  • 22k
4 votes
Accepted

UART (not the board itself) stopped working after connecting 5V to GND, can it be recovered?

If a UART GPIO is damaged that is a permanent failure and can not be fixed. In fact the damage can spread to adjacent GPIO causing them to fail and eventually the whole board may be damaged. To check ...
joan's user avatar
  • 71.1k
3 votes

How to set non standard serial port speed

The clock speed of the serial port is 3000000Hz (3MHz). We can UNDERclock this (as low as 1MHz), but we cannot OVERclock it (with any confidence). So we will pick the Baud Rate one-above the speed you ...
BlueChip's user avatar
3 votes
Accepted

How to communicate between Pi 3 and an Arduino using UART from GPIO?

Use one of the solutions mentioned in How do I make serial work on the Raspberry Pi3 If it still doesn't work please include a photo of your set-up and the details of which serial port you are using.
joan's user avatar
  • 71.1k
3 votes

Pi 3 Boot with UART console

I found answer here: https://openenergymonitor.org/emon/node/12311 Briefly it's due to Pi 3 default enable bluetooth which supplants uart on GPIO 14/15. So we need to disable bluetooth.
William Lai's user avatar
3 votes

read a RFID card MiFare 1k classic through a PN532 uart reader with serial.read()

The PN532 has multiple interfaces and can do a lot more than just "read" a card. So it implements a serial protocol that requires you send it commands asking it to do something and give you a ...
Patrick S.'s user avatar

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