I am running BBB SPI as slave but using the opposite direction for the data
pins:
0x150 0x30 /* spi0_sclk.spi0_sclk, INPUT_PULLUP | MODE0 */
0x154 0x10 /* spi0_d0.spi0_d0, OUTPUT_PULLUP | MODE0 */
0x158 0x30 /* spi0_d1.spi0_d1, INPUT_PULLUP | MODE0 */
0x15c 0x30 /* spi0_cs0.spi0_cs0, INPUT_PULLUP | MODE0 */
I think your way can work fine too, it just requires setting up the right
values in the SPI control registers.
But to make mine work as slave, I had to use mmap to directly access the SPI
hardware registers. I can do that from user-space because the protocol I
designed for my SPI hardware has no realtime requirements that would require
interrupts. (The packets in both directions always fit in the FIFOs, and run
in a half-duplex command/response mode.)
I don’t think any Linux SPI drivers support slave mode, and there is even an
explanation available from Linus Torvalds if you search the web. If you need
interrupts for more demanding performance, you will have to write your own
driver.
From: [email protected]
Sent: Saturday, April 12, 2014 1:39 AM
To: [email protected]
Subject: [beagleboard] Reading over SPI with Beaglebone Black as Slave
Im trying to use the Beaglebone Black as a slave device and read from the
arduino over SPI.
Im confused as to why I am just getting 255 repeated over and over on the
terminal as an output.
My thought is that there is some kind of a memory leak or buffer overflow. I
just can not figure out what
I'm doing wrong. Is one supposed to set cs as input? even with it set to output
I have the same issue.
I have my dts file set as:
/dts-v1/;
/plugin/;
/ {
compatible = "ti,beaglebone", "ti,beaglebone-black";
/* identification */
part-number = "spi0pinmux";
fragment@0 {
target = <&am33xx_pinmux>;
__overlay__ {
spi0_pins_s0: spi0_pins_s0 {
pinctrl-single,pins = <
0x150 0x30 /* spi0_sclk, INPUT_PULLUP | MODE0 */
0x154 0x30 /* spi0_d0, INPUT_PULLUP | MODE0 */
0x158 0x10 /* spi0_d1, OUTPUT_PULLUP | MODE0 */
0x15c 0x30 /* spi0_cs0, INPUT_PULLUP | MODE0 */
>;
};
};
};
fragment@1 {
target = <&spi0>;
__overlay__ {
#address-cells = <1>;
#size-cells = <0>;
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&spi0_pins_s0>;
spidev@0 {
spi-max-frequency = <24000000>;
reg = <0>;
compatible = "linux,spidev";
};
};
};
};
My Arduino is wired up like so:
P9.22 SPI0_CLK - Orange - 0x150 0x30 --> Arduino Due 110 SCLK
P9.21 SPI0_D0 - Green - 0x154 0x30 --> Arduino Due 109 MOSI
P9.18 SPI0_D1 - White - 0x158 0x10 --> 108 MISO
P9.17 SP0_CS0 - Black - 0x15C 0x30 ---> Pin 10 Set as Slave Select
Python File:
import spidev
import time
spi = spidev.SpiDev()
spi.open(1,0)
while True:
resp = spi.readbytes(1)
print resp[0]
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