Questions tagged [c]
For questions pertaining to compiling C programs on the Raspberry Pi.
278
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Unable to control TFT screen using RP2040
I am tinkering with the raspberry pi pico (the one with RP2040 chip). I am trying to use a TFT 1.24 screen controlled by the GC9A01A driver. I have followed the datasheet and the code I was able to ...
0
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53
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For Baremetal Raspberry Pi Zero 2W, how can I use GPIO pins?
I did find the Megathread on RPI forums
https://forums.raspberrypi.com/viewtopic.php?f=72&t=72260
and many tutorials but I can't seem to make them work
I wanted to follow this tutorial, https://...
0
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0
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28
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Square signal generated by Pico has unexpected waveform
I developed a small program for the Raspberry Pico using the Wokwi online simulator but when I tried to use the actual device it didn't work.
I started by debugging the signal generated with a logical ...
- 1
0
votes
1
answer
894
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Current proper way to interface GPIO from C code?
I've done a lot of googling and it's only confused me further. The old /sys/class/gpio way is deprecated and there's a rag-tag bunch of libraries that appear to have sprung up, none of which have much ...
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1
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1
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132
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It is possible to set I2C bus speed programmatically without the bcm2835 library?
All, I've ported a C++ OLED library from the bcm2835 library to use i2c-smbus to prevent having to run the executable as root. (not the best from a security standpoint). However, i2c-smbus and ioctl() ...
- 125
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1
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423
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The 'i2c_write_blocking' function in Pico SDK
I am confused... I'm using the i2c_write_blocking function, but getting a strange result:
If I do this - everything works as it should; i.e. I can read the values back from CONFIG_REG, and they match ...
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43
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Control Signal Raspbery Pi
I have a project to generate DCC signal so it needs to be used bts7960 to control the signal and connected to Raspberry Pi 3B. But, unfortunately the signal wave is not like digital signal perfectly. ...
1
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0
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69
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How do I directly process live raw camera data on the GPU without it passing though the CPU?
My understanding of the how a Raspberry Pi camera attached to the CSI port of the Pi works is that the raw data from it ends up directly in the GPU where it is slightly processed and compressed before ...
- 11
1
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0
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310
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Raspberry Pi Pico w bluetooth doesn't pair
I'm trying to set up bluetooth with the pico w with the c/c++ sdk for it to communicate wirelessly with my laptop.
I'm using btstack's and rasberry pi's example of spp_streamer.c. Also shown here.
The ...
1
vote
2
answers
953
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One time timer interrupt? (Pico W, C/C++)
Is there a way to set a one time timer interrupt on the Raspberry Pi Pico? I.e. in code, I would be able to tell the hardware timer to interrupt me in a specified period of time. Example pseudocode ...
- 21
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1
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351
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Get package temperature of a Raspberry Pi pico using C
I'm working on a Raspberry Pi pico and I'm using the C pico-sdk. I want to get the temperature of my package so I followed the datasheet of the rp2040 (page 565) and I've used the following code :
...
- 23
1
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1
answer
1k
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Update software of a Pico remotely
I'm using a raspberry Pi Pico and I'm struggling to find if it's possible to update my script remotely (I cannot use neither SWD or USB). Currently my new firmware (can be .uf2, .bin or .hex file) is ...
- 23
1
vote
0
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109
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bash who command does not give datetime correctly on testing
Edit : We are still looking for differences that would explain why who does not work on testing for user lines (it works for boot lines for instance), this is differences on the code for following ...
- 145
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1
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791
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How to receive data longer than 32bytes through PICO UART?
I have wrote a code to process data received in a PICO from Raspi PI. I have a slider which sends number to the PICO(through UART) to set some values. If the slider is dragged slowly or clicked the ...
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1
answer
107
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SOLVED Raspberry Pi 4 missing reverse ticks from AB encoder
I posted this on stack exchange, but it isn't getting much traction so I'm posting here, hopefully someone has run into this before!
I am writing a program to control a robot in C using a raspberry pi,...
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2
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417
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Pico Debugger can upload code once but not twice (when touching sysclk)
I've been playing around with the new Pico Debugger, and it is very nice. I have been running into some issues when using an external GPIO clock as the debugger does not seem able to detect the CPU's ...
- 191
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2
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141
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Why 10% CPU when sleep() on Pi 1B
I'm writing a simple application in C to handle switching relays on an old Pi 1B. When the Pi is supposed to wait for the next action to handle, I use the sleep() system call. I checked with top, only ...
- 111
1
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0
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56
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Respond to GPIO in fastest way possible
I'm trying to respond to a trigger from a ~1MHz clock and I'm having trouble doing this in the time required (under 400ns). I'm using a Raspberry Pi 3b+ and I've seen benchmarks of 50Mhz+ for toggling ...
- 111
1
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1
answer
1k
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How do I check the memory written into a Raspberry Pi Pico W from the compiler?
I'm uploading a simple C program into a Raspberry Pi Pico and I would like to check the memory this program is occupying in the Pico.
The program only has an empty main function. What I want to do is ...
- 21
1
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1
answer
60
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Using C on RPI to Initiate a File Transfer from Raspberry Pi to PC [closed]
As the title suggests, I would like to have the RPI initiate a file transfer to the PC. I am thinking to make a system() call inside the C code running on the RPI. I have established an SSH connection ...
- 21
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1
answer
661
views
Identify the Pico core at runtime
Using the C/C++ Pico SDK, how can I find out which core my code is running on?
(Specifically, I'd like to use lwIP's LWIP_ASSERT_CORE_LOCKED, which requires a thread or core identifier to determine ...
-1
votes
1
answer
378
views
fatal error: dht11.h: No such file or directory
I have written the following code:
// wiring schema:
// DHT11 --> Raspberry Pi
// PIR --> Raspberry Pi
// Servo Motor --> Raspberry Pi
#include <stdio.h>
#include <stdlib.h>
#...
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3
votes
1
answer
2k
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High Impedance (Hi-Z) state for Pico GPIO
Using a Pico [RP2040], I wish to interface to a data bus which is (already) pulled high.
(Based on the contents of the address bus) I want to put data on the data bus [ie. "memory mapped i/o"...
- 61
1
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0
answers
399
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Pico C programming: Make all projects use the USB port
I'm in the learning process for the RPi Pico using the C SDK. So far, the interesting examples I've followed output their results over the serial port. I've learned that some of the examples include a ...
- 22.6k
1
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1
answer
2k
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Raspberry Pico SDK - I2C Write to one Register Address (to set mode) then Read data from 2nd Register Address
I'm a bit confused by i2c_write_blocking() and how to specify the device_address, register_address and data to prime a device for reading and then to read data from another 2nd_register_address in the ...
- 125
0
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2
answers
821
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How to simultaneously control over 200 GPIO pins while maintaining timing accuracy
I am currently using a raspberry pi zero, which I connect directly to my computer via usb. I have connected eight MCP23017 GPIO expander chips, which is the maximum amount you can connect to a single ...
- 169
-1
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1
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783
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Why is GCC not able to compile file on arm64 Raspbian Bullseye?
I tried to run a simple program with gcc on my Raspbian 64bit on Pi 4.
Is there something wrong with my gcc installation?
pi@RPi64: $ cat h.c
#include <stdio.h>
int
main (void)
{
printf (&...
- 309
1
vote
1
answer
970
views
Can't generate PWM output on RP2040 other than square waves
I was playing with PWM on the RP2040. I can do square waves, but pretty much everything else does not work. I have recorded the PWM output with a sound card at 44100 Hz in order to verify it visually. ...
0
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0
answers
209
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C programming - Cannot open /dev/ttyS0 in blocking mode
I am trying to open /dev/ttyS0 in order to write over serial GPIO pin 8. I am using the Raspberry Pi Zero W and noted something strange. When I try to open dev/ttyS0 in nonblocking mode, I am able to ...
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1
vote
1
answer
793
views
rPi Pico IRQ with callback freezes Pico
I am trying to configure rp2040 function gpio_set_irq_enabled_with_callback on Pico using Arduino IDE with installed Arduino mbed OS because i need some libraries.
When called interrupt happens but ...
- 21
2
votes
1
answer
3k
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How to store an array in flash memory (only) using the pico sdk?
The RP2040 on my board (Seeeduino XIAO) comes with 2MB of flash ram.
How can I store an array that is too large to fit into RAM in flash, using C and the pico sdk?
As the array exceeds a certain size, ...
0
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0
answers
673
views
Why does Pi Pico duplicate and mix-up characters received over UART when programmed in C?
I have a Raspberry Pi Pico whose Tx and Rx pins are wired to the Rx and Tx pins of a Wemos D1 Mini development board. The Wemos and the Pico are powered via an external 5V power supply (common ground)....
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2
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0
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788
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use internal clock (ROSC) to set system clock (clk_sys) to run at 32 MHz in RP2040
I am trying to set the system clock of my RP2040 to 32MHz using the internal clock(rosc) as source clock. When the pico board is powered on, the ROSC's frequency is around 5 MHz which lies in the ...
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45
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Message printed multiple times when pressing hard button with RaspBerry Pi
I'm trying to print a message every time a button is pressed, and so far it's working fine, but the message is printed several times (somewhere around 4000 times) and I'd like it to be printed only ...
2
votes
2
answers
4k
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Pi Pico: Software Reset using the C SDK?
I'm looking for a method/function to be able to reset a Raspberry Pi Pico via programming, using the Pic's C SDK. Is this possible?
There is a way to do it using python using machine.reset() but I can'...
1
vote
1
answer
322
views
Reading MCP23S17 port expander with pigpio
I'm trying to read from a handful of switches connected to a MCP23S17 port expander using pigpio, however I'm not getting any useful results. Whatever my switch values, I have 0 returned.
I've checked ...
- 115
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1
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191
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SOLVED Can ioctl(file,I2C_SMBUS,&args) be used to read MCP3221?
I've been using C code based on a convenient linux_i2c-dev.h, but there seems to be no function to read 2 bytes without sending a command byte first.
I want the code to work on both PI3s & PI4s.
...
- 69
1
vote
1
answer
484
views
Is t possible/feasible to use android's NDK toolchain to cross-compile for Pi?
That's it, really. I have an x86_64 host that already cross-compiles a C application for android's 4 supported architectures, could I use the existing toolchain to build armeabi-v7a for a Pi (running ...
- 151
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2
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2k
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Communication Raspberry Pico and 3B+
I recently bought a Raspberry Pico to increase the capacities of my oldest Pi3B + tenfold in terms of sensors, buttons, LEDs, GPIO, etc.
But I can not find for the moment any protocol or Bus allowing ...
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0
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1
answer
34
views
Pin 16 not lighting up
First time actually using the hedears on my raspberry pi zero w. These headers were soldered on when I got it.
When I connect my red lead to the 5v pin, it lights up, so the circuit's correct. When I ...
- 117
0
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1
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111
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Understand the plumbing behind running RasberryPI code from Freenove in Python
I have downloaded some pre-made code from Freenove - https://github.com/Freenove/Freenove_Ultimate_Starter_Kit_for_Raspberry_Pi
Freenove uses WiringPi. So I downloaded WiringPi and ran build.
Question ...
- 161
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0
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82
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Running "make" Produces Fatal Error [duplicate]
I'm currently trying to get my raspberry pi setup with a VPN. To do so I needed a DNS provider, and so I'm trying to use No-IP's services, and after downloading their files and running a make to start ...
0
votes
1
answer
635
views
Do `pthreads` work on the Pico with the native c++ SDK without posix?
I am trying to port AprilTags to the Pi Pico. This has a dependancy on pthreads.
As is outlined in this SO question pthreads needs a posix layer. However there is this youtube video showing it working ...
- 191
0
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1
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2k
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How to set an initial value of a variable of struct in C? [closed]
Im making a library for a raspberry pi program and im running into trouble of a struct variable having an initial value.
myLib.h
typedef struct {
int startingNumber = 0; // this throw an error in ...
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-1
votes
1
answer
619
views
Pi 4 doesn't recognize .o file format? [closed]
Was trying to compile some .c files along with one .o file using gcc, and it failed with an error message saying: .o file format not recognized.
The same files got compiled on centOS vm though.
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2
votes
1
answer
279
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my spidev code does not store the receive data
So i am using a trimmed down version of this code to do a spi transaction usin spidev. Here is my code
/*
* spi-driver-speed.c
* 2016-11-23
* Public Domain
*/
#include <stdio.h>
#include <...
- 75
0
votes
1
answer
2k
views
How to read any connected DS18B20 temperature sensors with C/C++
I'm new to the Raspberry Pi ecosystem so pardon me if I'm talking nonsense.
I want to read the temperature data from the connected DS18B20 sensors using C/C++.
I followed this schema to connect them:
...
- 103
0
votes
1
answer
252
views
Shutdown from C program
I'd love to do a proper shutdown of the Pi from a program (written in C) so that the only thing left to do is pull the power plug. Is this possible?
- 33
4
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3
answers
6k
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How do I implement an interrupt service routine on Raspberry Pi?
There are several libraries like WiringPi, RPi and pigpio, claiming to implement interrupt handling for GPIO signals. But as far as I can estimate, they all do polling on the pins, therefore implement ...
- 43
-1
votes
1
answer
1k
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Raspberry Pi Software Driven servo control with PWM using C and Wiring Pi LIbrary
I'm trying to get my raspi zero to move an SG90 PWM driven servo. I have achieved this with python already using the gpiozero library, so I know my hardware works but I am trying to do it with C using ...
- 119