Linux/AM5728: RS-485 communication

philos

Part Number: AM5728
Other Parts Discussed in Thread: BEAGLEBOARD-X15

Tool/software: Linux

I have follow these links

1.my am57xx-beagle-x15-revc.dts is like:

	myuart10_pins_default: myuart10_pins_default {
		pinctrl-single,pins = <
			DRA7XX_CORE_IOPAD(0x3558, PIN_OUTPUT | MUX_MODE14)  /*gpio3_29*/
			DRA7XX_CORE_IOPAD(0x3688, PIN_INPUT | MUX_MODE3)	/*uart10_rxd*/
			DRA7XX_CORE_IOPAD(0x368C, PIN_OUTPUT | MUX_MODE3)	/*uart10_txd*/
		>;
	};

&uart10 {
	pinctrl-names = "default";
	pinctrl-0 = <&myuart10_pins_default>;
	
	rts-gpio=<&gpio3 29 GPIO_ACTIVE_HIGH>;

    rs485-rts-active-high;
    rs485-rts-delay = <1 1>;

	/*Enable RS-485*/
	linux,rs485-enabled-at-boot-time;

	status = "okay";
};

2.I have selected omap_driver

change "CONFIG_SERIAL_8250_OMAP = y " to " CONFIG_SERIAL_8250_OMAP = n"
change "CONFIG_SERIAL_OMAP = n " to " CONFIG_SERIAL_OMAP = y"

And I successfully use it to send out data.

But,I am unable to read from uart10 ,I simply connect uart10' txd with uart10' rxd.

error output of read function is:

read :: Resource temporarily unavailable
[19 9:14:19]Timeout in USBRead(): Data requested is 8 bytes, but you get only -1 bytes!

Help, I have no idea now, let me know if you need know my code.

over 5 years ago

0 philos over 5 years ago

Intellectual 520 points

Hello ,me again.
I open up uart8,uart9 in dtbs and found they work just fine.
but uart10 still can't receive data.
I am using beagleboard-x15,will this be a hareware bug? Ps:I have two bb-x15，their uart10 both not working for reception.

0 Pavel Botev over 5 years ago in reply to philos

TI__Guru**** 170625 points

Hi Philos,

Do you use AM57x PSDK v4.03 (link below)?
software-dl.ti.com/.../index_FDS.html

Note that UART pinmux should be done in u-boot-spl, not in kernel, see below e2e thread:
e2e.ti.com/.../661048

Check if UART10 is enabled in PRCM, check register CM_WKUPAON_UART10_CLKCTRL. Then you can check UART10 pinmux registers (i.e. CTRL_CORE_PAD_GPIO6_14) in user space with devmem2 tool, and verify you still have the correct and expected values. Then you can check UART10 module registers and compare the values with UART9.

See also below e2e threads:

e2e.ti.com/.../580226
e2e.ti.com/.../692735
e2e.ti.com/.../588951

Regards,
Pavel

0 philos over 5 years ago in reply to Pavel Botev

Intellectual 520 points

Hi Pavel:

Thinks for your reply,sorry to disturb you on weekend.

Right now I am using ubuntu-16.04.3-minimal-armhf-2017-10-10 on my bb-x15.I try to follow your advice ,install devmem2,and access uart10_clkctrl ,uart9_clkctrl,uart8_cklctrl,value are 0x02.
the value of pinmux register is also correct ,rightnow I use pinmux register vin2a_d2 for uart10

ubuntu@arm:~$ sudo devmem2 0x4ae07880 h
[sudo] password for ubuntu: 
/dev/mem opened.
Memory mapped at address 0xb6fc2000.
Value at address 0x4AE07880 (0xb6fc2880): 0x2
ubuntu@arm:~$ 
ubuntu@arm:~$ sudo devmem2 0x4a0098e0 h
/dev/mem opened.
Memory mapped at address 0xb6f21000.
Value at address 0x4A0098E0 (0xb6f218e0): 0x2
ubuntu@arm:~$ sudo devmem2 0x4a0098e8 h
/dev/mem opened.
Memory mapped at address 0xb6f2e000.
Value at address 0x4A0098E8 (0xb6f2e8e8): 0x2

And here is the information of interrupts running on my system.

0 Pavel Botev over 5 years ago in reply to philos

TI__Guru**** 170625 points

Philos,

Sorry for late reply, I was out of office.

If you can switch to TI PSDK (Arago Linux), we can be in better help. Ubuntu Linux is supported by BeagleBoard community, not by TI.

You can check UART10 module registers and compare the values with UART9.

Regards,
Pavel

0 Biser Gatchev-XID over 5 years ago

TI__Guru**** 393215 points

Closing this thread.

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Linux/AM5728: RS-485 communication