1 產品介紹
- 1.1 產品特性(Features)
- 1.2 產品官網連結(Product information Link)
2 接口布局和尺寸(Layout and Sizes)
3 快速入门 (Quick Start)
4 Linux系统的基本使用(Linux System Basic Operating Method)
5 通用方法(General Method)
6 Linux BSP編譯方法(Linux BSP Compile Method)
- 6.1 Yocto 4.2
- 6.2 Yocto 4.0

產品介紹

產品特性(Features)

NXP Arm® Cortex®-A35 i.MX 8ULP Dual up to 1.0 GHz
1 x Arm Cortex-M33 core
Onboard LPDDR4 1GB, 2000MT/s memory
1 x 4 lane MIPI-DSI 1 x USB2.0, 1 x USB 2.0 OTG, 5 x UART, 2 x I2C, 24 x GPIO, 6 x PWM, 1 x CAN
Ultra small size form factor - OSM
Support Ycoto Linux and Microsoft Azure Sphere OS

產品官網連結(Product information Link)

ROM-2620

接口布局和尺寸(Layout and Sizes)

ROM-2620 接口布局圖 Board Dimension Layout

ROM-ED91 接口布局圖 Board Dimension Layout

主板内置插针式引脚排序方式 (Pin Header defination)

Internal I/O, Jummper/Switch List:

Label	Function	Label	Function
DCIN1401	12V DCIN connector	SW1301	BT0_CFG1/4, BT1_CFG6/7/9/11
COMB	RS232/422/485	SW1302	BT0_CFG0, BT1_CFG4/5, BOOT_SEL0#/1#, MOD_ON
COMA	RS232/422/485	SW1203	UARTB_MODE0, UART_MODE1
LAN	LAN Connector	SW1204	UARTB_TERM, UARTB_SLEW
USB1	USB2.0 port Connector	SW1206	U1205_RX_TERM, U1205_MODE2
USB0_OTG1	Micro USB Connector	SW1201	UARTA_MODE0, UART_MODE1
AJ	Line Out Connector	SW1202	UARTA_TERM, UARTA_SLEW
MIC	MIC Connector	SW1205	U1202_RX_TERM, U1202_MODE2
CAN	CAN Bus Connector	SW1303	Power button
COME_DEBUG	M-core debug console	SW1304	Reset button
COMC	COM	I2S_CN	I2S Connector
COMD	A-core debug console	CN501	CAN0_H, CAN0_L terminatl resistors
I2C1101	I2C Connector	SD_SLT	SD select
I2C1102	I2C Connector	GPIO1101	GPIO header
CN601	M.2 Key E Connector	SPI_CN1101	PWM header
CN701	MIPI-CSI Connector	CN1101	SPI header
LVDS	LVDS Connector	LVDS_VDD_SLT	LVDS power select select header
LVDS_BKLT_PWR	LVDS Backlight Connector	LVDS_BKLT_SLT	LVDS Backlight power select header
BAT1	Battery Connector

Rear I/O

LED Function List

Location	Function
PD1405	+V5_MOD
PD1502	+V3.3
PD1503	+V5

Switch Settings

接口引脚定義 (Connector Pin definitions)

机械尺寸 (Mechanical Characteristics)

ROM-2620

快速入门 (Quick Start)

系统下载 (OS Download)

'Linux系统 (Linux OS)'

Yocto 4.0: IoTGateway/BSP/Linux/iMX8/OS Support List 4.0 release ROM-2620 - ESS-WIKI (advantech.com.tw)

Yocto 4.2: IoTGateway/BSP/Linux/iMX8/OS Support List 4.2 release ROM-2620 - ESS-WIKI (advantech.com.tw)

Linux 燒錄方法 (Linux Flash eMMC Method)

使用Flash tool 燒錄鏡像到eMMC (Flash image into eMMC by Flash Tools)

Step0: 檢查SD卡在Linux 環境的代號 (check SD card symbol in Linux system)

Step1: 創造一張可開機的SD 卡 (Create a bootable SD card)

Command :

~$ sudo dd if=2620A1AIM34LIVC0054_iMX8ULP_1G_flash_tool/image/imx-image-full-imx8ulprom2620a1-20230627062759.rootfs.wic of=/dev/sde bs=1M conv=fsync status=progress

Step2: 將可開機的SD 卡插入底板SD卡卡槽(Plug the SD card into Carrier board 's SD card slot)

Step3: 確認開機選擇指撥開關

EMMC boot:	SW1301: 1_2_5_6 ON SW1302: 4_6 ON
SD boot:	SW1301: 1_2_3_4 ON SW1302: 4_6 ON
Serial download:	SW1301: All OFF SW1302: 5_6 ON

Step4:打開電源和終端機 (Turn on the Power & Terminal)

Step5: 複製flash tool到U盤中, 解壓縮flash tools檔案,(copy to USB Disk, then unzip the flash tools file)(Test with 32G SD card)

複製檔案到U盤中 (Copy the flash file to USB Disk), 解壓縮flash tool到home目錄(Unzip the file to home)

tar zxvf /run/media/New\ Volume-sda/2620A1AIM34LIVC0054_iMX8ULP_1G_flash_tool.tgz -C ~

5. 進入flsah tool下的mk_inand資歷夾, 執行指令./mksd-linux.sh /dev/mmcblk0燒錄image到eMMC(Connect USB Disk to ROM-2620 system, extract the flash tool and browser to mk_inand folder and execute flash shell script "./mksd-linux.sh /dev/mmcblk0"

解壓縮後如果沒有mksd-linux.sh檔案, 可以到以下連結下載並複製到mk_inand資料夾下(If there is no mksd-linux.sh file in mk_inand directory. Please download from the link below and place it in mk_inand directory:

mksd-linux.sh

ROM-2620	Device node
SD card	/dev/mmcblk2
eMMC	/dev/mmcblk0

6. 切換開機switch來設定成從eMMC開機(Change boot switch to boot from eMMC. Reboot system).

Debug 串口調試 (Debug port Setting)

以 Tera Term 为例介绍如何使用串口调试功能

   Baud Rate波特率：115200
   Data 数据位：8
   Parity 奇偶校验：无
   Stop 停止位：1
   Flow Control流控：无

Tera Term Tool

Check the Sriel port in Device Manager (查看PC端的串口号)：

if you can not identify the Serial device , please check your serial driver.

Debug port connection (串口連接)

Log into Terminal Tool (进入串口调试终端)：

Linux系统的基本使用(Linux System Basic Operating Method)

UUU 使用方法(USB Connection (OTG port))

Connect USB cable to USB OTG port.

Change boot switch to "SW1301 all OFF, SW1302: 5_6:on" to boot from force recovery mode.

Serial download:

SW1301: All OFF
SW1302: 5_6 ON

Download uuu tool from link below:

Releases · nxp-imx/mfgtools (github.com)

The uuu verison we tested is 1.4.193: uuu

uuu (Universal Update Utility) for nxp imx chips -- libuuu_1.4.193-0-ge56424c

Perpare uboot and image files below:

2620A1AIM34LIVC0064_iMX8ULP_1G_imx-boot.tgz
2620A1AIM34LIVC0064_iMX8ULP_1G_flash_tool.tgz

1. Download uuu

$ wget https://github.com/nxp-imx/mfgtools/releases/download/uuu_1.4.193/uuu
$ chmod a+x uuu
$ tar zxvf 2620A1AIM34LIVC0064_iMX8ULP_1G_imx-boot.tgz
$ tar zxvf 2620A1AIM34LIVC0064_iMX8ULP_1G_flash_tool.tgz

Type command below to flash eMMC:

$ sudo ./uuu -b emmc_all 2620A1AIM34LIVC0064_iMX8ULP_1G_imx-boot/imx-boot-imx8ulprom2620a1-1G.bin-flash_singleboot_m33 2620A1AIM34LIVC0064_iMX8ULP_1G_flash_tool/image/imx-image-full-imx8ulprom2620a1-20230901105531.rootfs.wic

Display Setting (ROM-2620)

U-boot Command :

Display

=> setenv fdtfile imx8ulp-rom2620-a1-lt9211.dtb
=> saveenv
=> boot

Audio(Audio Testing Methid)

# cat /proc/asound/cards

0 [sgtl5000 ]: sgtl5000 - sgtl5000
sgtl5000

# amixer set Mic 50%
# amixer set Lineout 100%
# amixer set PCM 100%

Record and playback:

# arecord -t wav -c 2 -r 44100 -d 10 /tmp/mic.wav

# aplay /tmp/mic.wav

M.2 WiFi/BT測試方法(M.2 WiFi/BT Testing Method)

Test Wi-Fi with EWM-W167 on C0048 version: Change SD_SLT to 2-3

=> setenv fdtfile imx8ulp-rom2620-a1-m2-sdio.dtb
=> saveenv
=> boot

In Linux user space:

# iwconfig
# ifconfig wlan0 up
# iwlist wlan0 scan | grep ESSID
# killall wpa_supplicant
# ifconfig wlan0 up
# wpa_passphrase "Pilimao" "0913079939" > /tmp/wpa.conf
# wpa_supplicant -BDwext -iwlan0 -c/tmp/wpa.conf
# udhcpc -b -i wlan0
# ping 8.8.8.8

Add name server: nameserver 8.8.8.8 in resolv.conf file

# vi /etc/resolv.conf
# ping google.com

Test BT:

# cd /opt/rtl8723bs_bt/
# ./start_bt.sh ttyLP0
# hciconfig hci0 up
# hciconfig
# bluetoothctl
# discoverable on
# pairable on
# scan on
# info 84:C5:A6:D3:AF:E4
# pair 84:C5:A6:D3:AF:E4
# connect 84:C5:A6:D3:AF:E4
# paired-devices
# disconnect 84:C5:A6:D3:AF:E4
# remove 84:C5:A6:D3:AF:E4

Test Wi-Fi with EWM-W194M201E Module (SDIO Interface)

Step 1: Press enter after boot. The system will stop at u-boot, and change dtb file by below command.

=> setenv fdtfile imx8ulp-rom2620-a1-m2-sdio-88w8997.dtb
=> saveenv
=> boot

Step 2: Install driver by below command.

# rmmod mwifiex_sdio mwifiex
# modprobe moal mod_para=nxp/wifi_mod_para.conf
# modprobe btnxpuart

Step 3: WIFI test command.

# ifconfig mlan0 up
# wpa_passphrase ASUS-917C qwert12345 > /tmp/wpa.conf
# wpa_supplicant -d -B -i mlan0 -c /tmp/wpa.conf
# udhcpc -i mlan0

Test Bluetooth with EWM-W194M201E Module (UART Interface)

Step 1: Please refer to above step 1.
Step 2: Please refer to above step 2.

Step 3: Bluetooth test command.

# hciconfig hci0 up
# bluetoothctl
# discoverable on
# pairable on
# scan on
[NEW] FC:18:3C:8D:75:F4 myphone
# scan off
# pair FC:18:3C:8D:75:F4
# connect FC:18:3C:8D:75:F4

Serial Port測試方法(Serial Testing Method)(COM A/C)

COMA	/dev/ttyLP0
COMB(M33 Domain)
COMC	/dev/ttyLP2
COMD	/dev/ttyLP1
COME_DEBUG	M33 debug port

RS-232 Loopback Test (eg. COMA: ttyLP0):

Step 1: First change ROM-ED91 SW1201 to ‘01’.
Step 2: Run test command.

# stty -F /dev/ttyLP0 speed 115200 -echo
# cat /dev/ttyLP0 &
# echo test > /dev/ttyLP0

RS-422 Test:

Step 1: First change ROM-ED91 SW1201 to ‘11’.
Step 2: Test RS-422 with Adam-4520. Connect Adam-4520 with COMA with DB9 as the following:

Adam-4520 RX- <-->ROM-2620 COMA DB9 Pin 1,
Adam-4520 RX+ <-->ROM-2620 COMA DB9 Pin 2,
Adam-4520 TX- <-->ROM-2620 COMA DB9 Pin 4,
Adam-4520 TX+ <--> ROM-2620 COMA DB9 Pin 3

Step 3: Run below command:

# stty -F /dev/ttyLP0 speed 115200 ignbrk -brkint -icrnl -imaxbel -opost -onlcr -isig -icanon -iexten -echo -echoe -echok -echoctl -echoke
# cat /dev/ttyLP0 &
# echo "Serial Test" > /dev/ttyLP0

RS-485 Test:

Step 1: First change ROM-ED91 SW1201 to ‘10’.
Step 2: Test RS-485 with Adam-4520. Connect Adam-4520 with COMA with DB9 as the following:

Adam-4520 Data- <-->ROM-2620 COMA DB9 Pin 1,
Adam-4520 Data+ <-->ROM-2620 COMA DB9 Pin 2

Step 3: Run below command:

# stty -F /dev/ttyLP0 speed 115200 ignbrk -brkint -icrnl -imaxbel -opost -onlcr -isig -icanon -iexten -echo -echoe -echok -echoctl -echoke
# cat /dev/ttyLP0 &
# echo "Serial Test" > /dev/ttyLP0

I2C測試方法(I2C Testing Method)

Step 1: Plug in ROM-EG70
Step 2: Test by below command (eg. I2C-6 I2C_1101):

# modprobe at24
# echo -n $'\x06\x05\x04\x03\x02\x01' > test
# dd if=test of=/sys/bus/i2c/devices/6-0050/eeprom
# hexdump -C /sys/bus/i2c/devices/6-0050/eeprom -n 64

USB測試方法(USB Testing Method)

USB disk test (USB 2.0)
Step 1: Issue the following command (lsusb -t) after inserting a USB disk into the USB 2.0 port to check if the USB device is listed. Step 2: Test (eg. if usb disk is /dev/sda)

# dd if=/dev/urandom of=data bs=1 count=1024
# dd if=/dev/sda of=backup bs=1 count=1024 skip=4096 # dd if=data of=/dev/sda bs=1 seek=4096
# dd if=/dev/sda of=data1 bs=1 count=1024 skip=4096 # diff data data1
# dd if=backup of=/dev/sda bs=1 seek=4096

RTC測試方法(RTC Testing Method)

Step 1: Set system time to current, then write to RTC

# date 021010452023 && hwclock -w && date

Step 2: Set one incorrect time, then read time from RTC to verify

# date 010100002000 && hwclock -r && date

eMMC/SD測使方法(eMMC/SD Testing Method)

Device Routes
eMMC: /dev/mmcblk0
SD: /dev/mmcblk2

Test (eg. emmc)

Step 1: Test command:

# dd if=/dev/urandom of=data bs=1 count=1024
# dd if=/dev/mmcblk0 of=backup bs=1 count=1024 skip=4096
# dd if=data of=/dev/mmcblk0 bs=1 seek=4096
# dd if=/dev/mmcblk0 of=data1 bs=1 count=1024 skip=4096
# diff data data1
# dd if=backup of=/dev/mmcblk0 bs=1 seek=4096

乙太網路使用方法(Ethernent Testing Method)

Command : ifconfig

Command: Ping - I eth1 8.8.8.8 or Ping - I eth0 8.8.8.8

GPIO使用方法(GPIO Operating Method)

GPIO pin:

GPIO1101 pin	Pin Name	CPU Ball Name	GPIO number
1	GPIO_A_0	PTC0	416
2	GPIO_A_1	PTC1	417
3	GPIO_A_2	PTC2	418
4	GPIO_A_3	PTC3	419
5	GPIO_A_4	PTC4	420
6	GPIO_A_5	PTC12	428
7	GPIO_B_0	PTC18	434
8	GPIO_B_1	PTC19	435
9	GPIO_B_2	PTC20	436
10	GPIO_B_3	PTC21	437(Use for M2_SDIO_RST)
11	GPIO_B_4	PTC22	438(Use for M2_W_DISABLE2)
12	GPIO_B_5	PTC23	439(Use for M2_W_DISABLE1)
13	GPIO_B_6	PTB0	448
14	GPIO_B_7	PTB1	449
15	GPIO_C_0	PTD12	140
16	GPIO_C_1	PTD13	141
17	GPIO_C_2	PTF1	193
18	GPIO_C_3	PTF7	199(Use for LVDS_Bridge_RST)
19	PTB6	PTB6	454
20	PTA5	PTA5	485

GPIO Loopback Test (Using GPIO1 and GPIO2 as examples)

Step 1: Connect GPIO1 and GPIO2

Step 2: Export GPIO interface

# echo 416 > /sys/class/gpio/export
# echo 417 > /sys/class/gpio/export

Step 3: Set GPIO direction

# echo out > /sys/class/gpio/gpio1/direction
# echo in > /sys/class/gpio/gpio2/direction

Step 4: Read value and set output value than check

# cat /sys/class/gpio/gpio2/value 0
# echo 1 > /sys/class/gpio/gpio1/value
# cat /sys/class/gpio/gpio2/value
1

Camera使用方法(Camera Testing Method)

MIPI-CSI0 (Tested with OV5640 + mini-SAS to MIPI-CSI Cable): OV5640 CSI (CN701): Connect OV5640 camera to EG-55 CAM3

Step 1: Take pictures

# gst-launch-1.0 v4l2src num-buffers=1 device=/dev/video0 ! video/x-raw,width=640,height=480 ! jpegenc ! filesink location=sample.jpeg

Step 2: View on panel

# gplay-1.0 sample.jpeg

PWM測試方法(PWM Testing Method)

Please use oscilloscope to check waveform.

PWM1:

# echo 4 > /sys/class/pwm/pwmchip0/export
# echo 1000000 > /sys/class/pwm/pwmchip0/pwm4/period
# echo 500000 > /sys/class/pwm/pwmchip0/pwm4/duty_cycle
# echo 1 > /sys/class/pwm/pwmchip0/pwm4/enable

PWM2:

# echo 5 > /sys/class/pwm/pwmchip6/export
# echo 1000000 > /sys/class/pwm/pwmchip6/pwm5/period
# echo 500000 > /sys/class/pwm/pwmchip6/pwm5/duty_cycle
# echo 1 > /sys/class/pwm/pwmchip6/pwm5/enable

PWM3:

# echo 2 > /sys/class/pwm/pwmchip6/export
# echo 1000000 > /sys/class/pwm/pwmchip6/pwm2/period
# echo 500000 > /sys/class/pwm/pwmchip6/pwm2/duty_cycle
# echo 1 > /sys/class/pwm/pwmchip6/pwm2/enable

PWM4:

# echo 3 > /sys/class/pwm/pwmchip6/export
# echo 1000000 > /sys/class/pwm/pwmchip6/pwm3/period
# echo 500000 > /sys/class/pwm/pwmchip6/pwm3/duty_cycle
# echo 1 > /sys/class/pwm/pwmchip6/pwm3/enable

PWM5:

# echo 4 > /sys/class/pwm/pwmchip6/export
# echo 1000000 > /sys/class/pwm/pwmchip6/pwm4/period
# echo 500000 > /sys/class/pwm/pwmchip6/pwm4/duty_cycle
# echo 1 > /sys/class/pwm/pwmchip6/pwm4/enable

M33 Function

We use default M-core firmware to verify each of IO feature. User should connect COME_DEBUG port to PC and there were show screen as demonstration below:

Press C for test mode of CAN bus
Press Q for test mode of QSPI
Press M for test mode of LPSPI master
Press S for test mode of LPSPI slave
Press U for test mode of LPUART
About this firmware, user should note that if you want to switch to another test mode, you must reboot the system.

CAN Bus

Step 1: Prepare two pcs rom-2620. One for ‘Node A’ one for ‘Node B’
Step 2: Connect these two boards (HI-HI/LO-LO)
Step 3: The test steps and screen are as below :

Step 4: Follow the figure (step1 - step4). If B node received data means test successful.

QSPI

Step 1: After select the test mode ‘Q’ to verify QSPI, you will see below screen.

Step 2: This test program will perform QSPI erase/write automatically and show ‘successfully’ when it’s done.
Step 3: User can press any key to run again.

LPSPI

Step 1: Two pcs rom-2620. One for ‘Master’ one for ‘Slave’.
Step 2: Connection with these two boards by SPI Bus as below:

LPSPI3_PCS0 -- LPSPI3_PCS0
LPSPI3_GND -- LPSPI3_GND
LPSPI3_PCS1 -- LPSPI3_PCS1
LPSPI3_SCK -- LPSPI3_SCK
LPSPI3_SOUT -- LPSPI3_SIN
LPSPI3_SIN -- LPSPI3_SOUT

Step 3: One board select mode ‘M’ to be Master.
Step 4: The second board is specified to Slave by select mode ‘S’.
Step 5: The test screen as below:

Step 6: Press any key at terminal of node master, it will execute the test again.

LPUART

Step 1: Change ROM-ED91 SW1203 to '01'.
Step 2: Connect COM-B and COM-E to PC.
Step 3: Set RTS/CTS flow control for COM-B in Putty.exe

Step 4: After select the test mode ‘U’ to verify LPUART2, you will see below screen.

Step 5: If tester can input any characters/strings and show that at COM-B means test successful.

遠程訪問及文件傳輸(Remote Access and File Transimmion)

查看主板IP位址 ( Chech IP Address )：

        Command : ifconfig

SSH访问及文件传输

SSH Remote Log into Device

SSH远程登录,以putty选择putty.exe(或者使用Xshell、SecureCRT等类似软件)
需要设置远程设备的IP、通讯端口(默认22)、通讯方式，登录后验证用户名密码

通用方法(General Method)

查看CPU温度(Check CPU Temperature)

root@imx8ulprom2620a1:~# cat /sys/devices/virtual/thermal/thermal_zone0/temp
37000

查看内存容量(Check Memory Capacity)

root@imx8ulprom2620a1:~# free -h
               total        used        free      shared  buff/cache   available
Mem:           895Mi       230Mi       469Mi        29Mi       195Mi       546Mi
Swap:             0B          0B          0B
root@imx8ulprom2620a1:~#

查看存储容量(Check Storage Capacity)

root@imx8ulprom2620a1:~# df -hT
Filesystem     Type      Size  Used Avail Use% Mounted on
/dev/root      ext4       15G  3.9G  9.5G  30% /
devtmpfs       devtmpfs  431M  4.0K  431M   1% /dev
tmpfs          tmpfs     448M     0  448M   0% /dev/shm
tmpfs          tmpfs     180M   20M  160M  11% /run
tmpfs          tmpfs     4.0M     0  4.0M   0% /sys/fs/cgroup
tmpfs          tmpfs     448M   76K  448M   1% /tmp
tmpfs          tmpfs     448M  1.5M  447M   1% /var/volatile
tmpfs          tmpfs      90M  4.0K   90M   1% /run/user/0
/dev/mmcblk0p1 vfat       84M   32M   52M  38% /run/media/boot-mmcblk0p1
/dev/mmcblk2p2 ext4       29G   11G   17G  40% /run/media/root-mmcblk2p2
/dev/mmcblk2p1 vfat       84M   32M   52M  38% /run/media/boot-mmcblk2p1
root@imx8ulprom2620a1:~#

設置RTC (RTC Setting)

root@imx8ulprom2620a1:~# systemctl stop ntpdate.service
root@imx8ulprom2620a1:~# date 090816072021 && hwclock -w && date
Wed Sep  8 16:07:00 UTC 2021
Wed Mar  6 04:31:37 UTC 2024
root@imx8ulprom2620a1:~# date
Wed Mar  6 04:31:44 UTC 2024
root@imx8ulprom2620a1:~#

查看系統時間 (Check the system)

root@imx8ulprom2620a1:/# timedatectl
[ 41.402592] kauditd_printk_skb: 6 callbacks suppressed
[ 41.402611] audit: type=1334 audit(45.332:16): prog-id=15 op=LOAD
[ 41.417884] audit: type=1334 audit(45.344:17): prog-id=16 op=LOAD
Local time: Thu 1970-01-01 00:00:46 UTC
Universal time: Thu 1970-01-01 00:00:46 UTC
RTC time: Thu 1970-01-01 00:00:45 <----- Real-Time Clock，RTC
Time zone: Universal (UTC, +0000) <------ Time zone 目前
System clock synchronized: no
NTP service: active
RTC in local TZ: no

Note :

Change Time Zone

<code data-highlighted="yes">sudo timedatectl set-timezone "Asia/Taipei"
</code>

Local time: Fri 2024-05-03 09:07:42 CST Universal time: Fri 2024-05-03 01:07:42 UTC RTC time: Fri 2024-05-03 09:07:42 Time zone: Asia/Taipei (CST, +0800) System clock synchronized: yes NTP service: active RTC in local TZ: yes

Time Zone List

$ sudo timedatectl list-timezones

Africa/Abidjan

Africa/Accra

Africa/Addis_Ababa

Africa/Algiers

Africa/Asmara

Africa/Bamako

Africa/Bangui

Africa/Banjul

Africa/Bissau

Africa/Blantyre

Africa/Brazzaville

Africa/Bujumbura

Africa/Cairo

Africa/Casablanca

Linux BSP編譯方法(Linux BSP Compile Method)

ROM-2620 user guide

Contents