Hello Raju,

Let's back up and look at system design for a moment. It sounds like you are trying to reduce load on the ARM core, right?

Here is background info on PRU <-> ADC:

The post you linked is talking about controlling the on-processor ADC from PRU. You can find an example of that in the PRU Software Support Package (in Linux SDK under example-applications/pru-icss-x.x.x/ or at the git repo).

The PRU core runs bare metal code - you can't run Linux or RTOS on it like the ARM core.

You are trying to get the PRU to interact with an external ADC instead of the on-chip ADC.

One option is to use the PRU to control the SPI peripheral on the AM335x. I can give you pointers if that is what you want, but note that a peripheral should have only one master. So you would need to disable the SPI in the Linux DTS file and manually enable clocks, do peripheral initialization & setup, etc from PRU.

Another option is to directly connect the ADC to the PRU's GPI/GPO pins and control it by implementing a SPI protocol on the PRU. We have examples for that at https://www.ti.com/tool/TIDA-01555 and in the Linux SDK under example-applications/pru-adc.

Note that any PRU <-> ADC option you implement will take development work on your end. It will not be plug and play, like using a Linux driver.

Regards,

Nick

hii,

Thank You for Your Reply

Let's back up and look at system design for a moment. It sounds like you are trying to reduce load on the ARM core, right?

Yes

You are trying to get the PRU to interact with an external ADC instead of the on-chip ADC.

yes

One option is to use the PRU to control the SPI peripheral on the AM335x

yes that is what i'm trying to implement...

So you would need to disable the SPI in the Linux DTS file and manually enable clocks, do peripheral initialization & setup, etc from PRU.

yes i have comment spidev@1 node from dts file

Another option is to directly connect the ADC to the PRU's GPI/GPO pins and control it by implementing a SPI protocol on the PRU.

yes for that I'm thinking to use

in our custom board we have access  pru GPI/GPO

now i am thinking using bit-banging implement spi for External ADC interface

yes i am able to toggle PRU GPO at 5ns

#include <stdint.h>
#include <pru_cfg.h>

volatile register uint32_t __R30;
volatile register uint32_t __R31;

void main(void)
{
    volatile uint32_t gpo;

    /* GPI Mode 0, GPO Mode 0 */
    CT_CFG.GPCFG0 = 0;

   /* Clear GPO pins */
    __R30 = 0x0000;

    while(1){
         gpo = __R30;
         gpo ^= 0x1;
         __R30 = gpo;
         __delay_cycles(100000000); // half-second delay
         __delay_cycles(100000000); // half-second delay
    }
}

Hello Raju,

Apologies for the delayed response. If you decide to use PRU,

1) Note that you would either want to use the on-chip SPI, or you would want to directly connect the PRU GPI/GPO signals to the ADC. I do not think you would want to do both.

2) When disabling a node in the device tree, I do not suggest deleting the node. That is because there might be an earlier DTS file that enables the node. Instead, go to your last DTS file (explanation below). In the SPI node, change "status = "okay";" to "status = "disabled";"

Why use the last DTS file?
Let's say dts1 includes dts2 at the top of the file. And dts2 includes dts3 at the top of the file. Then the software will read dts3 first, then dts2, then dts1. If there is conflicting information, then the information from dts3 and dts2 will get overwritten by the information in dts1. That is why you want to make all your changes in dts1, so that what you do is not overwritten by a later file.

Regards,

Nick

hello Nick Saulnier

sorry for discrete information

initially i have connected external adc with on chip SPI1.0 pins

but problem was at that time due to spi load CPU used almost 70 to 80% seen in htop.

so i'm switched to use PRU GPI/GPO for ADC interface

1) Note that you would either want to use the on-chip SPI, or you would want to directly connect the PRU GPI/GPO signals to the ADC. I do not think you would want to do both.

==> would want to directly connect the PRU GPI/GPO signals to the ADC

yes

hello Nick Saulnier

thank you so much to guide with this matter...

your help really appreciated.

i am locking Build SPI Bit banging on PRU GPI/GPO.

for the time i am resolving my issue..

Thank You

Regards

Raju!..