You can sort of bit bang the slave selects, i.e. connect all the devices with shared MISO/MOSI/SCLK and ground but separate CS. Just set CS low for the device you want before calling the SPI driver. The SPI driver will try to set an CS but won't know it is not connected.
The Pis with the 40 pin expansion header have another SPI device with 3 ...
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 programmable
pulls), GPIO pins can be switched (multiplexed) into various other modes backed by dedicated
peripheral blocks such as I2C, UART and SPI.
The Raspberry Pis with the 40 pin expansion header do expose the GPIOs needed for the Pi to act as a SPI slave (GPIOs 18, 19, 20, 21).
See pages 102 and 160 SPI/BSC SLAVE BCM2835 ARM Peripherals.
However there is NO usable driver available for the Pi to act in this mode and personally I would not hold my breath waiting for one to appear.
See the latest ...
Yes the EEPROM can be written to. You can install the rpi-eeprom package and check the rpi-eeprom-update script to see how it is done. Apparently, you'll have to get the EEPROM image file from /lib/firmware/raspberrypi/bootloader/critical/, add whatever data you wanted, and then write it to the EEPROM using rpi-eeprom-update or flashrom command.
A SPI bus has usually the following signals
SCLK, The clock signal, driven by the master
CS, Chip select (CS) or slave select (SS), driven by the master, usually active-low and used to select the slave (since it is possible to connect multiple slave on the same bus).
MOSI, Master Out Slave In, driven by the master, the data for the slave will appear on this ...
The module spi-bcm2708 has been replaced with the updated kernel module spi-bcm2835.
Generally you should no longer load modules with modprobe or by putting them in /etc/modules (there are exceptions).
Recent kernels use a method called device tree.
SPI is now enabled by adding the following line to /boot/config.txt
Note, the above is ...
They are the SPI (Serial Peripheral Interface) interface pins. SPI is an interface bus used to exchange data between microntrollers and peripherals. It uses four pins MOSI which stands for master out slave in, MISO is Master in slave out, SS is slave select and a clock line (CLK).
You can read more on the SPI protocol on wikipedia and from sparkfun
As you have noticed the default maximum SPI transfer is 4096 bytes with the standard Linux driver.
To change the default add spidev.bufsiz=65536 to /boot/cmdline.txt and reboot. Where 65536 is the maximum size you want to allow.
Note that /boot/cmdline.txt is a single line. After the above change mine looked like:
dwc_otg.lpm_enable=0 console=tty1 root=/...
Any answer might only be of limited help to you as long as you have not understood how SPI actually works, so you should take a detailed look at this interface.
Concerning question 1:
SPI is a master-slave-system where any interaction has to be initiated by the master. The sensor itself is not able to write to the master, instead it is read by the master (...
Not impossible, but here are the obstacles to overcome:
First, the SD card knows nothing about FAT, ext4fs, or any other file system. What it does is accept commands from the host interface and either store the data given to it, or retrieve data and send them back to the host. The filesystem interface is implemented at a higher layer. Whatever you create ...
It looks you don't know what "clock" means. A clock is something that synchronizes. Say you are supposed to arrive at work at 9 o'clock. When your boss' clock reaches 9 o'clock, he will check if you are absent and flag you as arriving late if so. When your clock reaches 9 o'clock, you check if you have arrived and bang your head against the wall if not.
There are tradeoffs for each of the interfaces you mention:
UART: setting up and reading/writing fron/to a UART port is fairly easy. However, UARTs typically cannot be driven at very high speeds and there could be issues with baud rate inaccuracies as well as insuring that the baud rate is the same on both sides.
I2C: since the master drives the clock, ...
ALL the Pi GPIO are 3V3. NONE of them are tolerant of voltages outside the range 0 to 3.3V.
EDITED TO ADD:
The only pin which feeds into the Pi will be that connected to MISO (Master In Slave Out). The simplest thing to do is use a voltage divider on that line to cut the ADC 5V output to a Pi safe 3V3. A voltage divider is typically a pair of resistors.
Edit /boot/config.txt, add the following line, and reboot.
You should then have the following devices.
$ ls /dev/sp*
/dev/spidev0.0 /dev/spidev0.1 /dev/spidev1.0 /dev/spidev1.1 /dev/spidev1.2
Then try the Python spidev module.
In addition to the other answer about the SPI protocol I notice that the product page you linked to shows that, as well as the SPI CS pin on GPIO 15 (BCM22), the ADS1256 ADC has a "Data Ready" pin connected to GPIO 11 (BCM17). You could monitor this and only fetch a new sample when the data is available rather than just reading the data back constantly --- ...
You are right that the RaspberryPi does provide only two chip selects at its SPI bus (see here). And I assume that the SPI drivers and software solutions rely on that fact (although @joan's answer suggests that different libraries handle it differently and the official driver will allow arbitrary GPIO pins to be used as chip selects in the future).
You have ...
SPI is still supported, however recent versions of Raspbian have changed how SPI and other interfaces are enabled. To enable SPI run sudo raspi-config
select option 9 Advanced Settings
then option A6 SPI
Choose Yes to enable the SPI Interface
Then Yes to load the module by default
Finally click Finish to exit raspi-config and reboot.
A MOSI, MISO, CS and CLK are pins of SPI (Serial Peripheral interface protocol)protocol. SPI uses those separate pins to communicate with the target device. The fullform of those pins are serial clock (CLK), Master Input Slave Output (MISO), Master Output Slave Input (MOSI) and Chip Select (CS).
A CLK pin which provides timing information. A MOSI pin ...
I doubt you can disable device tree anymore, that was intended to be a temporary directive to smooth the introduction of device tree.
Just add the device tree SPI entry. Do not use gpio load spi. That is deprecated.
As long as there /dev/spidev* entries you can use SPI.
remove device_tree= from /boot/config.txt
add dtparam=spi=on to /boot/...
The following will work to allow you to use as many devices as you can find spare GPIO.
Find 8 spare GPIO (i.e. not being used by SPI or anything else in your project). Do not use or connect CE0.
I will refer to them as G1 to G8.
Connect the slave select (or whatever it is called for your chips) of ADC1 to G1, ADC2 to G2, ..., ADC8 to G8.
Connect the ...
I have exactly the same problem. Two different NRF24L01 modules. Raspbian stretch worked in the beginning, since the last update no more.
I use https://github.com/Gadgetoid//py-spidev/archive/master.zip
together with https://github.com/BLavery/lib_nrf24
This seems to be on the SPI level.
According to Raspberry Pi Foundation:
The SPI master driver is disabled by default on Raspbian. To enable
it, use raspi-config, or ensure the line dtparam=spi=on isn't
commented out in /boot/config.txt, and reboot. If the SPI driver
was loaded, you should see the device /dev/spidev0.0.
So, try to reboot your board after enabling SPI.
It was a stupid error on my side.
SPI_IOC_MESSAGE ioctl call expects pointer to the first spi_ioc_transfer element in the argument.
I passed a pointer to pointer instead, because I saw many samples passing &array there, and I’ve forgot about this. I’ve fixed my C++ code, and it works now.
Meanwhile, cat /dev/spidev0.0 & command still prints ...
As far as I am aware you will need to bit bang the protocol yourself. This will mean that you will only be able to reliably support comparatively low clock rates.
The Pi contains hardware to support SPI in a slave mode but it does not appear to work. This post on the raspberrypi.org forums documents my unsuccessful attempts to drive the hardware from ...
The main SPI hardware has two preset chip selects.
The auxiliary SPI hardware has three preset chip selects.
You can ignore the presets and use your own GPIO, but you will have to switch them yourself. The hardware automatically switches the presets.
The current Linux driver makes no use of this anyhow. It switches the chip selects manually. You can tell ...
You have misunderstood the usage of the set and clear registers.
If bit x is 1 in the set register then GPIO x is set high. If bit x is 0 then the level of GPIO x is not affected (i.e. if high it stays high, if low it stays low).
If bit x is 1 in the clear register then GPIO x is set low. If bit x is 0 then the level of GPIO x is not affected (i.e. if ...
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 & TX) adapters which works fine. I use 8 to 24 of them on several products I support on a Raspberry Pi. At the slow rate of 9600, the Pi will not have ...