Save the below code as spidev_test.c on to your Raspberry Pi and compile it
gcc spidev_test.c -o spidev_test
Running
Plug your Arduino to your desktop via the serial cable. Open the arduino Serial Monitor and set the bitrate to 115200. Now, on the Raspberry Pi, run the compiled code
sudo ./spidev_test
You should see HELLO WORLD print in the Arduino IDE Serial Monitor.
Debugging
Make sure that your kernel has the required drivers (spi-bcm2708.ko and spidev.ko)
[email protected] ~/spi $ ls -al /lib/modules/`uname -r`/kernel/drivers/spi/
total 64
drwxrwxr-x 2 pi pi 4096 Aug 10 10:53 .
drwxrwxr-x 23 pi pi 4096 Aug 10 10:53 ..
-rw-rw-r– 1 pi pi 14428 Aug 10 10:53 spi-bcm2708.ko
-rw-rw-r– 1 pi pi 10852 Aug 10 10:53 spi-bitbang.ko
-rw-rw-r– 1 pi pi 15803 Aug 10 10:53 spidev.ko
-rw-rw-r– 1 pi pi 10693 Aug 10 10:53 spi-gpio.ko
Wow, can the 3.3V RPi tolerate the 5V TTL levels of the Arduino?
meyers
Hmm from http://elinux.org/RPi_Low-level_peripherals “The pins use a 3V3 logic level and are not tolerant of 5V levels, such as you might find on a 5V powered Arduino.”.
Let me try and find out from some friends and colleagues why this works and doesn’t blow up 🙂
Julian
Accidentally put 5V on the GPIO Pins of mine and didn’t blow up either 😉
“Non tolerant” doesn’t mean it will blow up right away, just shorten the Pi’s life span. Use a logic level converter like http://www.adafruit.com/products/395 to supply the right voltage levels.
TJ
Many N-Channel Enhancement Mode MOSFETs can also be used for level shifting, some of them costing only the loose change in your back trouser pocket.
It would be interesting to learn how the spi-kernel-driver might be used to
read an SPI ADC (e.g. ADS1100). Additionally this would be more save for the hardware, because this ADC works on 2.7 to 5.5V. Where to find more documentation and/or examples using this kernel-driver ? Thank you!
im beginner doing spi interface. i tried with above code to start learning. i connected wires as described but i got o/p “can’t able open device”. one thing which is different from above of mine is the broadcom pheripheral mine is BCM2835. is there any change in the code for my bcm. and one more thing spi may be blacklisted when i google for solution how to unlock them. and not able to find spidev under dev. how to resolve it?
meyers
You can observe the blacklisting or not of the spi drivers by following the guide above. Specifically, the lsmod section. Don’t think of blacklisting a driver as locking but rather as a convenience mechanism for specifying that a driver not be loaded when the distribution starts up for one reason or another.
After you have verified the driver is loaded ensure that the driver created the device nodes. Specifically /dev/spidev0.0
Let me know if you have further problems.
venkatesh
when i try lsmod, i cant find spidev0.0 how to load it. please guide me. for lsmod i got this
now im getting output
“can’t open device : permission denied”
meyers
Try prepending the command you are running with sudo. For example if you are running the command ‘ls’ try ‘sudo ls’.
venkatesh
had u wrote code for receiving data from arduino?
parvathi
how did u get spi enabled? when i am trying to install spi_bcm2708 i am getting “unable locate package spi_bcm2708″… please guide me..
meyers
Arduino example spi receiver code is included in The above tutorial.
venkatesh
two things i want to clarify with you. im sending command byte 0xFE from rpi after its received in arduino im sending {0xAA,0xAB,0xAC} from arduino
1. while transmitting a buffer why its necessary to add 0x0A at the end of the buffer (arduino) when i look at serial monitor it shows 0xAA,0xAB,0xAC “0x0A” 0xAA,0xAB,0xAC if 0x0A is added it sendinding as 0xAA,0x0A,0xAB,0x0A.
2.while receiving in rpi, each received byte in sent buffer follwed by command byte(0xFE) for 9 times. eg: if im receiving in rpi as 0xAA 0xFE 0xFE 0xFE 0xFE 0xFE 0xFE 0xFE 0xFE 0xFE 0xAB…….
venkatesh
sorry in 1. if 0x0A is not added it sending as 0xAA,0x0A,0xAB,0x0A.
I am pretty new to programming. I have a device which I want to connect to the RPi using SPI. I tried out the spi_devtest.c and it works. But the SPI frame of the slave device requires 24 bits. I have searched high and low and have not been able to find a solution. I tried changing the number of bits per word but that does not work. I wonder if I would have to just send 3 bytes instead of 24 bits. In that case, I don’t know how to send 3 bytes without the chip select going inactive after each word. Any help would be greatly appreciated.
TT or anyone. I have the same issue of requiring 24 bits without raising syncb. Do tell how you “figured it out”. Wondering if I can use a different gpio bit and create and control my own sincb, but this seems ugly.
Sorry for taking so long to respond, I ended up just sending 3 8bit words. I don’t know if there’s any other way to do it, or if there exists a better way.
venkatesh
why the byte being returned back to rpi which sent to arduino? is any voltage converter required?
I have some errors while compiling the RasPi code..
They are: [email protected] ~ $ gcc spidev_test.c -o spidev_test
spidev_test.c:234:13: error: redefinition of ‘pabort’
spidev_test.c:26:13: note: previous definition of ‘pabort’ was here
spidev_test.c:240:20: error: redefinition of ‘device’
spidev_test.c:32:20: note: previous definition of ‘device’ was here
spidev_test.c:242:16: error: redefinition of ‘bits’
spidev_test.c:34:16: note: previous definition of ‘bits’ was here
spidev_test.c:243:17: error: redefinition of ‘speed’
spidev_test.c:35:17: note: previous definition of ‘speed’ was here
spidev_test.c:246:13: error: redefinition of ‘transfer’
spidev_test.c:38:13: note: previous definition of ‘transfer’ was here
spidev_test.c:279:13: error: redefinition of ‘print_usage’
spidev_test.c:71:13: note: previous definition of ‘print_usage’ was here
spidev_test.c:295:13: error: redefinition of ‘parse_opts’
spidev_test.c:87:13: note: previous definition of ‘parse_opts’ was here
spidev_test.c:364:5: error: redefinition of ‘main’
I got the /dev/spidev0.0 and spidev0.1. The RasPi is updated and everything is ok, except the “[email protected] ~/spi $ ls -al /lib/modules/`uname -r`/kernel/drivers/spi/” part, where I only get: “total 64”.
Hello,
Great tuto, just may be asking a stupid question but there is no wire with CE0 ou CE1 between the Arduino and the PI, does the arduino hardware SPI work even if the Chip Enable pin is floating ?
Thanks
I get this error: spi_slave.ino: In function ‘void setup()’:
spi_slave:24: error: ‘SPCR’ was not declared in this scope
spi_slave:24: error: ‘SPE’ was not declared in this scope
spi_slave:24: error: ‘_BV’ was not declared in this scope
spi_slave.ino: In function ‘void SPI_STC_vect()’:
spi_slave:39: error: ‘SPDR’ was not declared in this scope
Does anyone know what could be the problem and/or know how to fix this? I’m using this code with the arduino due
Hi, awesome job here!! I got this working nicely. I am working on a new pi project that is coded in C++ and I am having issues integrating. I’ve tried linking the the above pi C code to my C++ code but get “undefined reference” to the C function (from pi code). Can anyone help convert the above Raspberry Pi code into C++? It will be greatly appreciated! Thank You
JR
Hello,
I’m looking to do this exact some thing (use SPI between a Pi and an Arduino). But something might’ve happened to this post. The Arduino code seems to have gone missing from this post. If someone could repost this, I’d appreciate it.
Jmg
How to convert hello word to the uint8_t . I’m planning to mod spidev_test to send data in argument
pischky
Just have got it running on an AlaMode Board from wyolum. One note:
Pull the SS input (Arduino Pin 10) input down to ground by some jumper.
Gregory
How did you get to the conclusion? What happens if you don’t?
Thank you
The transfer does not work. May be you have luck sometimes and the input is floating to ground. Better than pulling SS to ground is using one extra level shifter from Pi pins CS0 or CS1. Level shifter for other pins are includes on AlaMode Board.
PROTECT your 3,3V I/O Pins on Raspi… at least with 5kOhms…
(+ live coding with Mathematica/Wolfram)
Hello,
please, if you don’t have anything else available, at least introduce series resistors.
This limits the current when accidentally “Out LOW” meets “Out HIGH” or Out5V meets In3.3V.
Current on input shall not exceed 1mA. Makes 5kOhms. OK, 4,7kOhm. Works, if no real fast signals or Pull up/downs or bad EMI-noisy environments are involved.
The bus transceiver does a 3,3V job in both directions. So the 5V device has to cope with a HIGH signal of 3.3V.
If the switching hysteresis of the 5V device are OK with this, it is a no-delay fast bidirectional (without having to set direction, has no input for this) thingy to use, more stable than the auto-magic bidirectional true level-shifters also available, which might oszillate when wires are to long or PCB design is not really HF-reflection-proof; and to admit, my lousy breadboard without ground plane underneath, well, did not have the mony for the 3M breadboard… 😉
(Only the cmos specs state 0,3*VCC and 0,7*VCC for LOW and HIGH. Thats not quite achieved…)
Why not let arduino run at 3,8V ? Would mitigate things 😉 (Tip I read: best _not_ to translate, meaning not having to translate 😉
Good luck!
(We can not run on 5V till end of days, so I sighed and bougt a due and a raspi, no conversion problem; still this is seemingly a contradiction, both beeing 32bit bla… but I want to program Arduino from Mathematica / Wolfram.
Then Mathworks can be the frontend for a digital/analog workbench, with full force analysis (and synthesis) at hand. http://www.wolfram.com/raspberry-pi/?source=footer
and https://reference.wolfram.com/language/ref/device/Arduino.html
where they explain how arduino is controlled via serial, but also gets a new c++ program uploaded when the changes in wolfram demand it.
Should ask them if it could be done via debugging mode code insertion ;))
Still don’t know if DUE is supportet. Maybe not yet.
(Matlab/Simulink have this in their classroom licence for schools, it is part of their product named “coder”. Supporting coding for Raspi, Arduino, Lego Mindstorms EV3. It uploads code, afterwards target system runs the program, if wanted, autonomously or with communication.
What’s missing for me is cpld and the analog programming cypress pSoC4.. offers, but with more cells, at least a few k.)
Fred
May you help me?
Have you used wiringPi?
I am trying to establish a connection between both arduino and raspberry, but i only get garbage.
So I have some questions:
1) Where is the Slave Select pin?
2) Can I turn the Arduino using only the SPI?
3) How to I set the comunication speed on arduino?
4) Why do I only get garbage?
Always excercise caution when working with electronics. All software is provided on an "as is" basis without warranty of any kind, express or implied. Unless otherwise noted, all code content is licensed under the Apache 2.0 license
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