Grinberg: /* GPIO */

2017-07-16T15:31:34Z

‎GPIO

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== Overview ==
The example run-time Yocto Linux filesystem image for the CompuLab CM-T43 System-on-Module / Computer-on-Module is based on Texas Instruments Arago project.

The Automatic Installation page provides a brief introduction on how to install the run-time Yocto Linux image.

== Using Yocto Linux on CM-T43 ==

=== Connection and Logging In ===
Use the following username to login:

<pre>
root@cm-t43: root
</pre>

To login into the Linux system, you may use a serial console (ttyO0) at 115200 bps, or connect through the network.

=== Networking ===
CM-T43 can operate in two modes: dual MAC mode, or as a 3 port ethernet switch. The default mode of operation is dual MAC mode.
A user guide for both operation modes can be found in the [http://processors.wiki.ti.com/index.php/Linux_Core_CPSW_User%27s_Guide Linux Core CPSW User's Guide] article in the TI wiki.
To configure networking, edit {{filename|/etc/network/interfaces}}, {{filename|/etc/resolv.conf}}, {{filename|/etc/hostname}} and {{filename|/etc/hosts}}. For more information about Linux network configuration read [http://www.debian.org/doc/manuals/reference/ch05.en.html Network setup] chapter in the [http://www.debian.org/doc/manuals/reference/index.en.html Debian Reference].

==== Switching to 3-port switch mode ====
To enable 3-port switch mode, the device tree blob must be modified to remove the dual_emac property before Linux boots. This can be done using the following U-Boot commands:
<pre>
# fdt addr <address fdt was loaded to>
# fdt rm /ocp/ethernet@4a100000 dual_emac
</pre>

=== Wayland display server ===
The Arago root filesystem image contains fully featured display server system Wayland/Weston.
Wayland is a protocol that specifies the communication between a display server (called Wayland compositor) and its clients, as well as a reference implementation of the protocol.
The Wayland project includes a demo Wayland compositor, called Weston. It's fast, small, and runs on embedded and mobile devices.
On start-up Wayland and the Texas Instruments Matrix is started.
Connect USB mouse and keyboard for interaction with Wayland and the Texas Instruments Matrix.
*Use the following commands to stop the matrix:
<pre>
/etc/init.d/matrix-gui-2.0 stop
</pre>
*Use the following commands to start the matrix:
<pre>
/etc/init.d/matrix-gui-2.0 start
</pre>
*Use the following commands to stop the Weston:
<pre>
/etc/init.d/weston stop
</pre>
*Use the following commands to start the Weston:
<pre>
/etc/init.d/weston start
</pre>

=== Display options ===
CM-T43 evaluation platform has three video output interfaces: LCD, DVI, and LVDS. Default configuration of Yocto Linux for CM-T43 uses LCD as primary video output.

=== USB Dual-Role-Device ===

CM-T43 has USB DWC3 based controller. It features USB 2.0 Dual-Role-Device (DRD) subsystem with integrated HS/FS (USB2.0) PHY.
CM-T43 DRD port is USB host and USB device (gadget) capable. USB Device Gadget drivers are compiled as modules with default CM-T43 kernel configuration.
Current Linux kernel support of DWC3 features does not allow dynamic role (host/device) switching during runtime. By default, ''host'' role is assigned to CM-T43 DRD port.

Device mode can be enabled by running the following U-Boot commands before boot:
<pre>
# fdt addr <address fdt was loaded to>
# fdt resize
# fdt set /ocp/omap_dwc3@48380000/usb@48390000 dr_mode peripheral
</pre>

==== Testing Device (gadget) mode ====

Default CM-T43 kernel configuration enables {{filename|g_serial}}, {{filename|g_mass_storage}}, {{filename|g_ether}}, {{filename|g_audio}}, and {{filename|g_hid}} gadget drivers.
More gadget drivers can be enabled in the kernel configuration.

* Connect USB OTG micro B-cable (ID pin Float) to P3 USB DRD port of SB-SOM baseboard.
* Connect other side Standard-A connector to Linux Host PC USB Host port.

===== Emulate a serial link =====

* Load gadget driver on CM-T43 Eval board:
<pre>
root@cm-t43:~# modprobe g_serial
[ 56.306729] g_serial gadget: Gadget Serial v2.4
[ 56.311433] g_serial gadget: g_serial ready
[ 56.758367] g_serial gadget: high-speed config #2: CDC ACM config
</pre>

* Ensure the connection is established on the Host PC:
<pre>
user@linux-host:~$ dmesg
...
[72415.607738] cdc_acm 2-1.8.2:2.0: ttyACM0: USB ACM device
[72415.608446] usbcore: registered new interface driver cdc_acm
[72415.608447] cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters
</pre>

* Receive data on CM-T43 Eval board:
<pre>
root@cm-t43:~# cat /dev/ttyGS0
</pre>

* Send data from Host PC:
<pre>
user@linux-host:~$ echo "Test message" > /dev/ttyACM0
</pre>

=== Analog Audio ===
CM-T43 provides an analog audio interface, which is registered as a standard ALSA sound card. Use '''aplay -l''' to list all soundcards and digital audio devices registered on the system:
<pre>
root@cm-t43:~# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: CMT43SoundCard [CM-T43-Sound-Card], device 0: davinci-mcasp.0-wm8731-hifi wm8731-hifi-0 []
Subdevices: 1/1
Subdevice #0: subdevice #0
</pre>

==== Analog Audio Settings ====
To enable the Analog audio playback, {{cmd|alsamixer}} or {{cmd|amixer}} applications can be used.
* {{cmd|alsamixer}} - set the “''Output Mixer''” control on.
or
* {{cmd|amixer}} - set the “''Output Mixer HiFi Playback Switch''” control on using command line interface:
<pre>
root@cm-t43:/# amixer cset numid=13 1
numid=13,iface=MIXER,name='Output Mixer HiFi Playback Switch'
; type=BOOLEAN,access=rw------,values=1
: values=on
</pre>

==== Analog Audio Playback ====
In order to play back a sound file make use of the {{cmd|aplay}} application.
<dl>
* {{cmd|aplay -L}} can be used for listing of all pcm devices.
</dl>
Here is a sample output of {{cmd|aplay -L}} command:
<pre>
root@cm-t43:/# aplay -L
null
Discard all samples (playback) or generate zero samples (capture)
pulse
PulseAudio Sound Server
default:CARD=CMT43SoundCard
CM-T43-Sound-Card,
Default Audio Device
sysdefault:CARD=CMT43SoundCard
CM-T43-Sound-Card,
Default Audio Device
</pre>

=== WiFi ===
CM-T43 features 802.11b/g/n wireless connectivity solution, implemented with a Marvell wireless controller module.

==== WiFi Initialization ====
* The driver gets loaded automatically. Make sure that the WiFi driver is loaded:
<pre>
root@cm-t43:/# lsmod | grep mwifi
mwifiex_sdio 26039 0
mwifiex 256669 1 mwifiex_sdio
cfg80211 259154 1 mwifiex
</pre>
* {{cmd|iwconfig}} command from {{cmd|wireless-tools}} package can be used to retrieve detailed information about the WiFi interfaces:
<pre>
mlan0 IEEE 802.11abgn ESSID:off/any
Mode:Managed Access Point: Not-Associated
Retry short limit:9 RTS thr=2347 B Fragment thr=2346 B
Encryption key:off
Power Management:on
</pre>

* WLAN interface activating:
<pre>
root@cm-t43:/# ifconfig mlan0 up
</pre>
* Sample WiFi scanning:
<pre>
root@cm-t43:/# iwlist mlan0 scan
</pre>
The output will show the list of Access Points and Ad-Hoc cells in range.
For more information about connecting to wireless networks and tuning WiFi interfaces refer to “wpa_supplicant” and “wireless-tools” man pages.

=== Bluetooth ===
==== Host Controller Interface (HCI) Initialization ====
* HCI requires no user interaction for being configured. The driver gets loaded automatically unless this option has been disabled by putting a black list rule for this device.<br>
Make sure that the Bluetooth driver is loaded:
<pre>
root@cm-t43:/# lsmod | grep btmrvl
btmrvl_sdio 14518 0
btmrvl 12690 1 btmrvl_sdio
bluetooth 326343 16 bnep,btmrvl,btmrvl_sdio
</pre>

* HCI device configuration utility can be run to retrieve detailed information about the Bluetooth interfaces:
<pre>
root@cm-t43:/# hciconfig -a
hci0: Type: BR/EDR Bus: SDIO
BD Address: 80:D2:1D:5F:45:18 ACL MTU: 1021:7 SCO MTU: 120:6
UP RUNNING PSCAN
RX bytes:1704 acl:0 sco:0 events:76 errors:0
TX bytes:1459 acl:0 sco:0 commands:75 errors:0
Features: 0xff 0xfe 0x8f 0xfe 0xdb 0xff 0x7b 0x87
Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3
Link policy: RSWITCH HOLD SNIFF
Link mode: SLAVE ACCEPT
Name: 'cm-t43-0'
Class: 0x000100
Service Classes: Unspecified
Device Class: Computer, Uncategorized
HCI Version: (0x8) Revision: 0x8300
LMP Version: (0x8) Subversion: 0x7270
Manufacturer: Marvell Technology Group Ltd. (72)
</pre>

* If the HCI device is not running, use the below command to enable the HCI device:
<pre>
root@cm-t43:/# hciconfig hci0 up
</pre>

* HCI inquire remote devices
<pre>
root@cm-t43:/# hcitool scan
Scanning ...
</pre>

=== RTC ===
==== Accessing and setting the RTC ====
To access the RTC time and date run:
<pre>
root@cm-t43:/# hwclock
Sat Jun 17 13:36:35 2017 0.000000 seconds
</pre>

To set the date and write it into the RTC do the following:
<pre>
root@cm-t43:/# date -s "2015-02-11 10:00:00"
Wed Feb 11 10:00:00 UTC 2015
root@cm-t43:/# hwclock -w
root@cm-t43:/# hwclock
Sat Jun 17 13:39:09 2017 0.000000 seconds
</pre>

=== Touchscreen ===

Touchscreen calibration runs on first boot. To rerun it, execute the following commands:
<pre>
rm /etc/udev/rules.d/ws-calibrate.rules
rm /run/media/mmcblk0p1/ws-calibrate.rules
reboot
</pre>

=== CAN bus ===

Install can-utils using:
<pre>
# apt-get install can-utils
</pre>

==== CAN interface configuration ====
* Load the can bus modules:
<pre>
root@cm-t43:~# modprobe can-raw
[ 123.114470] can: controller area network core (rev 20120528 abi 9)
[ 123.120993] NET: Registered protocol family 29
[ 123.155278] can: raw protocol (rev 20120528)
root@cm-t43:~# modprobe can-bcm
[ 145.749470] can: broadcast manager protocol (rev 20120528 t)
</pre>

It is recommended configure the CAN interface, with the {{filename|iproute2}} utilities.

* To make sure the right {{filename|ip}} utility is used, run:
<pre>
root@cm-t43:~# ip -V
ip utility, iproute2-ss160111
</pre>

* Configure the CAN interface bit-rate to 125 Kbits/sec (values of up to 1Mbit/sec are supported):
<pre>
root@cm-t43:~# ip link set can0 type can bitrate 125000
</pre>

* Enable the CAN interface:
<pre>
root@cm-t43:~# ip link set can0 up
[ 184.948857] net can0: c_can_hw_raminit_wait_syscon: time out
[ 184.954781] c_can_platform 481d0000.can can0: setting BTR=0518 BRPE=0000
</pre>

===== Send/Receive packets =====

Use {{filename|cansend}} and {{filename|candump}} utilities to send and receive packets via CAN interface.

* Send standard CAN frame (on the first device):
<pre>
root@cm-t43:~# cansend can0 111#1122334455667788
</pre>

* Send extended CAN frame (on the first device):
<pre>
root@cm-t43:~# cansend can0 11111111#1122334455667788
</pre>

* Dump all received data frames as well as error frames (on the second device):
<pre>
root@cm-t43:~# candump any,0:0,#FFFFFFFF
can0 111 [8] 11 22 33 44 55 66 77 88
can0 11111111 [8] 11 22 33 44 55 66 77 88
</pre>

=== GPIO ===

To use a GPIO:
* Select a pin you wish to use as GPIO by consulting the [http://www.compulab.com/products/computer-on-modules/cm-t43/#devres CM-T43 reference manual]. The reference manual contains a list of pins and the possible functions each pin can support, many of which include GPIO signals as one of the possible functions.
* Setup the pinmux so that the GPIO function is selected for the pin you chose in the previous step. This may require you to edit the device tree for CM-T43. Consult the [[Linux: Introduction to device trees | device tree article]] in the CM-T43 Linux wiki.
* Export the GPIO in Linux sysfs and cd into it
<pre>
root@cm-t43:/# echo <gpio_num> > /sys/class/gpio/export
root@cm-t43:/# cd gpio<gpio_num>
</pre>
* Select GPIO input/output function:
<pre>
root@cm-t43:/# echo in > direction
</pre>
or
<pre>
root@cm-t43:/# echo out > direction
</pre>
* To read GPIO input (or determine what value is being output):
<pre>
root@cm-t43:/# cat value
0
</pre>
* To output a value on the GPIO pin:
<pre>
root@cm-t43:/# echo 1 > value
</pre>

=== PRU ===

CM-T43 Yocto Linux has PRU support. For usage instructions, consult the [http://processors.wiki.ti.com/index.php/PRU-ICSS TI PRU wiki].

== See also ==

* [[CM-T43: Yocto Linux: Automatic Installation]]
* [[CM-T43: Yocto Linux: Manual Installation]]
* [[Linux: Development for ARM modules]]

[[Category:Linux]]
[[Category:Yocto]]
[[Category:CM-T43]]

CM-T43: Yocto Linux: User Space - Revision history

Grinberg: /* GPIO */