Requesting guidance for beaglebone black

kiranbv · April 16, 2021, 12:17pm

Hi,

We have made a custom board from beagle bone black. We have a requirement to use I2C1 on E17 and E18 pins of MPU. However, we see that all pins are reference w.r.t port 8 or port 9 in dts files.

I am using kernel_version of “4.14.108-ti-r140”, Debian 10 Root File System. The MPU is am3358bzcz100

I also have following questions :

The device tree files that is used by beagle bone black is taken from “ti-linux-kernel-dev/KERNEL/arch/arm/boot/dts”?
How can i modify the device tree so that i2c1 is enabled and available on E17 and E18 pins of MPU?

@RobertCNelson : Please help

Regards,
Kiran B V

RobertCNelson · April 16, 2021, 1:50pm

Using TI’s pinmux tool with the AM335x and ZCZ package we can configure E17/E18 as:

		pinctrl-single,pins = <
			AM33XX_IOPAD(0x96c, PIN_INPUT_PULLUP | MUX_MODE3) /* (E17) uart0_rtsn.I2C1_SCL */
			AM33XX_IOPAD(0x968, PIN_INPUT_PULLUP | MUX_MODE3) /* (E18) uart0_ctsn.I2C1_SDA */
		>;

Clone repo:

git clone -b ti-linux-4.14.y https://github.com/RobertCNelson/ti-linux-kernel-dev.git
cd ./ti-linux-kernel-dev/
./build_kernel.sh

Hit ESC, ESC, and Ctrl-C after menuconfig loads, then patch this file, under the KERNEL directory

diff --git a/arch/arm/boot/dts/am335x-bone-common.dtsi b/arch/arm/boot/dts/am335x-bone-common.dtsi
index 6e5b6ae03b59..ee4ba20d08a2 100644
--- a/arch/arm/boot/dts/am335x-bone-common.dtsi
+++ b/arch/arm/boot/dts/am335x-bone-common.dtsi
@@ -79,6 +79,13 @@
                >;
        };
 
+       i2c1_pins: pinmux_i2c1_pins {
+               pinctrl-single,pins = <
+                       AM33XX_IOPAD(0x96c, PIN_INPUT_PULLUP | MUX_MODE3) /* (E17) uart0_rtsn.I2C1_SCL */
+                       AM33XX_IOPAD(0x968, PIN_INPUT_PULLUP | MUX_MODE3) /* (E18) uart0_ctsn.I2C1_SDA */
+               >;
+       };
+
 //     i2c2_pins: pinmux_i2c2_pins {
 //             pinctrl-single,pins = <
 //                     AM33XX_PADCONF(AM335X_PIN_UART1_CTSN, PIN_INPUT_PULLUP, MUX_MODE3)      /* uart1_ctsn.i2c2_sda */
@@ -283,6 +290,14 @@
        };
 };
 
+&i2c1 {
+       pinctrl-names = "default";
+       pinctrl-0 = <&i2c1_pins>;
+
+       status = "okay";
+       clock-frequency = <100000>;
+};
+
 &i2c2 {
        pinctrl-names = "default";
        //pinctrl-0 = <&i2c2_pins>;

Then finish the build:

./tools/rebuild.sh

Regards,

kiranbv · April 21, 2021, 7:34am

Thanks a lot for the specific inputs. I used the TI’s pinmux tool to verify this on P9 of beagle-bone black since E17 and E18 are not accessible. And it is working as expected.

@RobertCNelson : However, in my last kernel build a virtual COM port was showing up when i booted the BBB (USB used for powering the BBB). Is there some specific kernel module that i need to select for this feature? Actually we require a COM port through USB for testing purposes.

kiranbv · April 21, 2021, 11:08am

I think there is some problem. The older image used “4.14.108-ti-r127” and i could see “[ OK ] Found device /dev/ttyGS0.” message. But its timing out in “4.14.108-ti-r140”. Please check the screenshot below.

RobertCNelson · April 21, 2021, 1:51pm

Hi @kiranbv i have not completely fixed the /dev/ttyGS0 issue… It’s a USB gadget driver we load at boot time, to provide a connection point between your pc and the board. systemd see’s it’s enabled, but is waiting for it to load…

loaded here:

github.com

RobertCNelson/boot-scripts/blob/master/boot/am335x_evm.sh#L508


			if [ ! "x${USB_NETWORK_CDC_DISABLED}" = "xyes" ]; then
				mkdir -p functions/ncm.usb0
				echo ${cpsw_4_mac} > functions/ncm.usb0/host_addr
				echo ${cpsw_5_mac} > functions/ncm.usb0/dev_addr

				ln -s functions/ncm.usb0 configs/c.1/
				usb1="enable"
			fi

			mkdir -p functions/acm.usb0
			ln -s functions/acm.usb0 configs/c.1/
		fi

		#ls /sys/class/udc
		#v4.4.x-ti
		if [ -d /sys/class/udc/musb-hdrc.0.auto ] ; then
			echo musb-hdrc.0.auto > UDC
		else
			#v4.9.x-ti
			if [ -d /sys/class/udc/musb-hdrc.0 ] ; then
				echo musb-hdrc.0 > UDC

Configured here:

github.com

RobertCNelson/boot-scripts/blob/master/boot/am335x_evm.sh#L799


    ifconfig eth0 down
    ifconfig eth0 hw ether ${cpsw_4_mac}
    ifconfig eth0 up || true    
fi

if [ "x${abi}" = "xab" ] ; then
	#Just Cleanup /etc/issue, systemd starts up tty before these are updated...
	sed -i -e '/Address/d' /etc/issue || true
fi

check_getty_tty=$(systemctl is-active serial-getty@ttyGS0.service || true)
if [ "x${check_getty_tty}" = "xinactive" ] ; then
	systemctl restart serial-getty@ttyGS0.service || true
fi

#20200404: let's disable this, as we now have an imgtec specific blend, with modules/package pre-installed..
#if [ -f /opt/sgx/status ] ; then
#	sgx_status=$(cat /opt/sgx/status || true)
#	case "${sgx_status}" in
#	not_installed)
#		if [ -f /opt/sgx/ti-sgx-ti335x-modules-`uname -r`*_armhf.deb ] ; then

github.com

RobertCNelson/boot-scripts/blob/master/boot/am335x_evm.sh#L406


		systemctl disable connman-wait-online.service || true
	fi
fi

#udhcpd gets started at bootup, but we need to wait till g_multi is loaded, and we run it manually...
if [ -f /var/run/udhcpd.pid ] ; then
	echo "${log} [/etc/init.d/udhcpd stop]"
	/etc/init.d/udhcpd stop || true
fi

if [ ! -f /etc/systemd/system/getty.target.wants/serial-getty@ttyGS0.service ] ; then
	ln -s /lib/systemd/system/serial-getty@.service /etc/systemd/system/getty.target.wants/serial-getty@ttyGS0.service
fi

run_libcomposite () {
	if [ ! -d /sys/kernel/config/usb_gadget/g_multi/ ] ; then
		if [ -f /usr/bin/bb_usb_gadget.sh ] ; then
			/usr/bin/bb_usb_gadget.sh || true
		else
			echo "${log} Creating g_multi"
			mkdir -p /sys/kernel/config/usb_gadget/g_multi || true

There is a patch for systemd:

github.com

rcn-ee/repos/blob/master/debian-10-systemd/suite/buster/debian/patches/0001-units-add-usb-gadget-target.patch

From daa5d901114beecdb3b412c2df6e95f971680008 Mon Sep 17 00:00:00 2001
From: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Date: Tue, 29 Jan 2019 11:13:44 +0100
Subject: [PATCH] units: add usb-gadget target

Linux can be run on a device meant to act as a USB peripheral. In order
for a machine to act as such a USB device it has to be equipped with
a UDC - USB Device Controller.

This patch adds a target reached when UDC becomes available. It can be used
for activating e.g. a service unit which composes a USB gadget with
configfs and activates it.
---
 man/systemd.special.xml   | 11 +++++++++++
 rules/99-systemd.rules.in |  2 ++
 units/usb-gadget.target   | 12 ++++++++++++
 3 files changed, 25 insertions(+)
 create mode 100644 units/usb-gadget.target

diff --git a/man/systemd.special.xml b/man/systemd.special.xml

This file has been truncated. show original

This isn’t fully ready yet…

Regards,

kiranbv · June 21, 2021, 4:03am

Hi Robert,

I used the pins A16 and B16 to verify this in beaglebone black since one of the pins (E18) is left open. And it worked as expected. However, our custom boards have come and when i used the code with A16 and B16 code modification, the i2c signals are not coming. Also, i have tried to probe TP9 test point to see if any i2c1 signals are coming on beaglebone black. Unfortunately, i do not see anything. In contrast, i can see the i2c signals on D17 and D18 (i2c2 module) pins with a oscilloscope.

Regards,
Kiran B V

RobertCNelson · June 21, 2021, 8:31pm

We make sure the i2c’s clocks are running in u-boot. Does your board share the BBB eeprom values or did you use something else?

Regards,

RobertCNelson · June 22, 2021, 1:34pm

Hi @kiranbv , looks fine, can you talk i2c from u-boot?

Regards,

kiranbv · June 24, 2021, 6:46am

Hi @RobertCNelson ,

When i try to use it from u-boot, i get the error : " pads on bus probably not configured (status=0x10)". Please check below for details

Regards,
Kiran B V

kiranbv · June 24, 2021, 7:56am

Also, i found this information from this link : https://e2e.ti.com/support/processors-group/processors/f/processors-forum/449928/i2c1-controller-pin-mux-issue-on-beagleboneblack-am335x

I think this could be the cause since i2c1 was working on the other pin. Please guide me to resolve this

RobertCNelson · June 24, 2021, 3:54pm

I can confirm the default version of u-boot we use on teh BBB show’s that same info…

Press SPACE to abort autoboot in 0 seconds
=> i2c dev 2
Setting bus to 2
=> i2c md.0 0x68 1
i2c_read: error waiting for addr ACK (status=0x116)
Error reading the chip: 1
=> i2c dev 1
Setting bus to 1
=> i2c md.0 0x68 1
i2c_read (addr phase): pads on bus probably not configured (status=0x10)
Error reading the chip: 2
=> i2c dev 0      
Setting bus to 0
=> i2c md.0 0x68 1
i2c_read: error waiting for addr ACK (status=0x116)
Error reading the chip: 1
=> version
U-Boot 2019.04-00004-g72e2ec7 (Jun 23 2021 - 14:54:50 -0500)

=> i2c bus
Bus 0:	omap24_0
Bus 1:	omap24_1
Bus 2:	omap24_2
=> i2c probe
Valid chip addresses: 24 34 50
=> i2c dev 1
Setting bus to 1
=> i2c probe
Valid chip addresses:i2c_probe: pads on bus probably not configured (status=0x10)
i2c_probe: pads on bus probably not configured (status=0x10)
i2c_probe: pads on bus probably not configured (status=0x10)

So, you’ll need to actually configure the bus…

Regards,

kiranbv · June 25, 2021, 8:56am

Hi @RobertCNelson,

I think the i2c1 module is configured since its usable on A16 and B16 pins. Also, i confirm that i2c1 module still works with A16 and B16 even E17 and E18 is used. I think this is similar to the problem reported here : https://e2e.ti.com/support/processors-group/processors/f/processors-forum/449928/i2c1-controller-pin-mux-issue-on-beagleboneblack-am335x

I think if we configure pinmux for i2c1 in u-boot, the conflict will get resolved. I am trying to find where this config is done, but not successful so far. Please help

Regards,
Kiran B V

RobertCNelson · June 25, 2021, 1:57pm

It is done in the board.c/.h and mux.c file’s:

github.com

beagleboard/u-boot/blob/v2019.04-bbb.io-am335x/board/ti/am335x/board.c#L71-L87


      
          #ifdef CONFIG_TI_I2C_BOARD_DETECT
          void do_board_detect(void)
          {
          	enable_i2c0_pin_mux();
          #ifndef CONFIG_DM_I2C
          	i2c_init(CONFIG_SYS_OMAP24_I2C_SPEED, CONFIG_SYS_OMAP24_I2C_SLAVE);
          #endif
          	if (ti_i2c_eeprom_am_get(CONFIG_EEPROM_BUS_ADDRESS,
          				 CONFIG_EEPROM_CHIP_ADDRESS))
          		printf("ti_i2c_eeprom_init failed\n");
          
          	//hack-ish, needs to mux'ed early, in do_cape_detect was too late...
          	enable_i2c2_pin_mux();
          #ifndef CONFIG_DM_I2C
          	i2c_init(CONFIG_SYS_OMAP24_I2C_SPEED2, CONFIG_SYS_OMAP24_I2C_SLAVE2);
          #endif
          }

board.h:

github.com

beagleboard/u-boot/blob/v2019.04-bbb.io-am335x/board/ti/am335x/board.h#L143-L144


      
          void enable_i2c0_pin_mux(void);
          void enable_i2c2_pin_mux(void);

Then the mux:

github.com

beagleboard/u-boot/blob/v2019.04-bbb.io-am335x/board/ti/am335x/mux.c#L110-L132


      
          static struct module_pin_mux i2c0_pin_mux[] = {
          	{OFFSET(i2c0_sda), (MODE(0) | RXACTIVE |
          			PULLUDEN | SLEWCTRL)}, /* I2C_DATA */
          	{OFFSET(i2c0_scl), (MODE(0) | RXACTIVE |
          			PULLUDEN | SLEWCTRL)}, /* I2C_SCLK */
          	{-1},
          };
          
          static struct module_pin_mux i2c1_pin_mux[] = {
          	{OFFSET(spi0_d1), (MODE(2) | RXACTIVE |
          			PULLUDEN | SLEWCTRL)},	/* I2C_DATA */
          	{OFFSET(spi0_cs0), (MODE(2) | RXACTIVE |
          			PULLUDEN | SLEWCTRL)},	/* I2C_SCLK */
          	{-1},
          };
          
          static struct module_pin_mux i2c2_pin_mux[] = {
          	{OFFSET(uart1_ctsn), (MODE(3) | RXACTIVE |
          			PULLUDEN | PULLUP_EN | SLEWCTRL)},	/* I2C_DATA */
          	{OFFSET(uart1_rtsn), (MODE(3) | RXACTIVE |

This file has been truncated. show original

github.com

beagleboard/u-boot/blob/v2019.04-bbb.io-am335x/board/ti/am335x/mux.c#L313-L322


      
          void enable_i2c0_pin_mux(void)
          {
          	configure_module_pin_mux(i2c0_pin_mux);
          }
          
          void enable_i2c2_pin_mux(void)
          {
          	configure_module_pin_mux(i2c2_pin_mux);
          }

github.com

beagleboard/u-boot/blob/v2019.04-bbb.io-am335x/board/ti/am335x/mux.c#L430


      
          			configure_module_pin_mux(mii1_pin_mux);
          		}
          		configure_module_pin_mux(mmc0_pin_mux);
          #if defined(CONFIG_NAND) && defined(CONFIG_EMMC_BOOT)
          		configure_module_pin_mux(nand_pin_mux);
          #elif defined(CONFIG_NOR) && defined(CONFIG_EMMC_BOOT)
          		configure_module_pin_mux(bone_norcape_pin_mux);
          #else
          		configure_module_pin_mux(mmc1_pin_mux);
          #endif
          		configure_module_pin_mux(i2c2_pin_mux);
          	} else if (board_is_pb()) {
          		configure_module_pin_mux(mii1_pin_mux);
          		configure_module_pin_mux(mmc0_pin_mux);
          	} else if (board_is_icev2()) {
          		configure_module_pin_mux(mmc0_pin_mux);
          		configure_module_pin_mux(gpio0_18_pin_mux);
          		configure_module_pin_mux(uart3_icev2_pin_mux);
          		configure_module_pin_mux(rmii1_pin_mux);
          		configure_module_pin_mux(spi0_pin_mux);
          	} else {

Regards,

kiranbv · June 29, 2021, 9:05am

Hi,

I made the changes

In board.h

In board.c

In mux.c : Checking on P9.17 (SPI0_CS0) and P9.18 (SPI0_D1)

But having the same error

Regards,
Kiran B V

kiranbv · June 29, 2021, 9:08am

Hi,

I found some fix. Posting here so that its useful for others. I am not sure if its the right way of doing it. Please suggest improvements.

Following changes in am335x-bone-common-univ.dtsi fixed the issue. Also, “sudo config-pin p9.17 i2cMod” and “config-pin p9.18 i2cMod” must be given before using the pins as i2c1.

Regards,
Kiran B V

Topic		Replies	Views
Enable Device Tree Overlay for Beaglebone Black linux 4.14-ti Linux Discussions	2	1563	October 12, 2021
Beagle Bone Black GPIO with Device Tree Overlay Linux Discussions	2	4289	May 30, 2018
BeagleBone Green SPI - How to swap D0 and D1? Linux Discussions	3	1835	February 26, 2021
BBAI and SPI/BONE-SPIx_x? Linux Discussions	5	1107	March 18, 2021
AM335x board starts kernel from SD card but uses distro from eMMC Linux Discussions	7	1548	September 26, 2022

Related topics