RTOS/AM3359: McSPI control from PRU

Hao Tan

Part Number: AM3359

Tool/software: TI-RTOS

Hi,

I want to use the PRU to control MCSPI0. I set clk, cs, d0, d1 all in 0x30 (rxactive, pullup) in device tree. In register cm_per_spi0_clkctrl (0x44e00004c) i wrote 0x2. Write 0 in PRU-ICSS CFG to ensure ocp master port is enabled.

I set some spi parameters, then open the channel, set CS to LOW, write data in TX.

I checked register mcspi_ch0stat, i can see, EOT is 1, TXS is 1, RXS is 1. I think this represents a successful SPI transfer. However, the 8-bit clk is not displayed on the oscilloscope. I tried disabling the SPI node in the device tree to ensure that linux does not control the SPI, but there is still no signal display.

My question is:

1. do I need some special settings when using SPI in a PRU? For example, CM_PER_L4LS_CLKSTCTRL or M_PER_L3S_CLKSTCTRL. Because I saw mcspi.c in Starterware, this example has bit0 and 1. set these registers.
2. I did not map the mcpsi interrupt to the pru interrupt, does this affect the clock output. I just want to complete a simple function: write the data in tx, and then transfer it to the slave.

I used the 05_03_00_07 RTOS_SDK in BBB

over 4 years ago

0 Garrett Ding over 4 years ago

TI__Mastermind 43296 points

Tan,

1. You should not need set CM_PER_L4LS_CLKSTCTRL or M_PER_L3S_CLKSTCTRL unless you need to controls the module to sleep/wake-up.

2. No, if just want to transmit the data in master mode, the clock output is relevant with the interrupt.

>>I set some spi parameters, then open the channel, set CS to LOW, write data in TX.

Do you have all these operated in PRU? Do you see CS behaves as expected?

Regards,
Garrett

0 Hao Tan over 4 years ago in reply to Garrett Ding

Prodigy 90 points

Hi, Garrett Ding，

I'm very happy to have received your response. Yes, I have done these operations in the PRU. When I change the FORCE bit of the MCSPI_CH0CONF register, I can see that the CS signal changes from LOW to HIGH, or from HIGH to LOW, but CLK does not change.

0 Hao Tan over 4 years ago in reply to Garrett Ding

Prodigy 90 points

If my understanding is not wrong: I must map the interrupt, if i want to transmit the data to slave. So I need to initialize the interrupt in the arm, and then map the interrupt in the PRU? Or map the interrupt directly in the PRU?

0 Garrett Ding over 4 years ago in reply to Hao Tan

TI__Mastermind 43296 points

You don't have to setup interrupt for transmitting data from master to slave. There are two interrupts for the master mode tx (TX_empty and TX_underflow).

You can always check the TXFFE field of SPI channel status register to see if the FIFO transmit buffer is empty.

Regards,

Garrett

0 Hao Tan over 4 years ago in reply to Garrett Ding

Prodigy 90 points

Hi, Garrett Ding,

i donot use FIFO. My problem is: i can see, when I open the channel and write the data in TX, I can see that TXS, RXS and EOT become 1, but the oscilloscope does not display the clock signal. I connected the MISO to the 3.5v pin. I can see that the value of RX is 0xff.

0 Garrett Ding over 4 years ago in reply to Hao Tan

TI__Mastermind 43296 points

Tan,

Alternatively you might want to use the bit-banging technique to use GPIO pins and emulate SPI communication -

Regards,

Garrett

0 Hao Tan over 4 years ago in reply to Garrett Ding

Prodigy 90 points

hi, Garrett Ding ,

thank you for your help, my program worked, but i cant transmit the second spi-word. After the first transmission i reset the MCSPI_IRQSTATUS, then write in TX again. I read TX, its the first data, not second. What other steps do i need?

Processors

Processors forum

RTOS/AM3359: McSPI control from PRU