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How to set up UART2 in J990

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{{Message/Information Message|title=TITLE|message=This How-To was tested under Kernel 2.6.35.y but content are valid for Kernel 2.6.37.y}}

= Overview =

This How-To is meant to be a starting point for people to learn to set up UART2 for IGEPv2 J990 connector as quickly and easily as possible. In this how-to, we use [http://releases.linaro.org/platform/linaro-m/headless/final/linaro-m-headless-tar-20101108-2.tar.gz Linaro Headless] with [[Linux Kernel 2.6.35.y|Kernel 2.6.35.y]]. This How-To is focused for revisions RC1/RC3/RC4/RC6 (WIFI/BT versions). <br>

More information about UART: [http://en.wikipedia.org/wiki/Universal_asynchronous_receiver/transmitter <span style="text-decoration: underline;">here</span>] and [[How to use UARTs|here]].'''<br>'''

There are three modes to configure UART2 in J990: via user space (fast modefirst way), editing only igep.ini (second way) or editing kernel source and compile it (slow modethird way) or editing only igep.ini  '''NOTE: '''UART2 in j990 connector has CMOS voltages (faster mode0V-1V8).

= Feedback and Contributing =

At any point, if you see a mistake you can contribute to this How-To.<br>

= Fast ModeFirst way<br> = First way: this mode has an issue, when your system reboot or shutdown you will need to configure again. Using user space to configure mux and disable bluetooth. <br>

Fast Mode: the problem of this mode is when your system reboot or halt you will need to configure again, but you configure four UART wires in J990. Using user space to configure mux and disable bluetooth. Default kernel&nbsp; has disabled TWL4030 PCM voice interface output pins to high impedance, otherwise this module forces the level of mcbsp3_fsx and mcbsp3_clkx pins. To make sure, go to ~/sound/soc/codecs/twl4030.c file already read: <br>

<pre> 0x04, /* REG_VOICE_IF (0xF) */</pre>

=== Configure IGEP ===

Make sure that If you use a IGEPv2 Expansion is disabledBoard, go to igep.ini file: don't use modem for this tutorial<pre>;buddy=igep0022 </prebr>  

'''Disable Bluetooth:'''

Log Logging with root user via SSH or Serial cable.<br> '''NOTE: '''Poky distribution does not have debug filesystem enabled. Mount it: <pre>mount -t debugfs none /sys/kernel/debug</pre>

Go to /sys/kernel/debug/omap_mux/<br>

Set sdmmc2_dat5 to gpio137 (mode 4):

<pre>echo 0x004 &gt; sdmmc2_dat5 </pre>

Check Revise that:

<pre>root@localhost:/sys/kernel/debug/omap_mux# cat sdmmc2_dat5

name: sdmmc2_dat5.gpio_137 (0x48002166/0x136 = 0x0004), b ah3, t NA

Set gpio137 to low value to disable bluetooth:

<pre>echo 0 &gt; /sys/class/gpio/gpio137/value</pre>

Check Revise that:

<pre>root@localhost:/sys/class/gpio# cat /sys/class/gpio/gpio137/value

0

echo 0x007 &gt; uart2_rx

echo 0x007 &gt; uart2_tx </pre>

Check Revise that:

<pre>root@localhost:/sys/kernel/debug/omap_mux# cat uart2_cts

name: uart2_cts.safe_mode (0x48002174/0x144 = 0x0007), b ab26, t NA

echo 0x101 &gt; mcbsp3_fsx

echo 0x101 &gt; mcbsp3_dr </pre>

Check Revise that:

<pre>root@localhost:/sys/kernel/debug/omap_mux# cat mcbsp3_dx

name: mcbsp3_dx.uart2_cts (0x4800216c/0x13c = 0x0101), b af6, t NA

root@localhost:/sys/kernel/debug/omap_mux#

</pre>

Mode will be 1 (uart mode)

= Faster Mode Second way<br> =

Faster modeSecond way: configure kernel via IGEP Xloader. Configuration will be permanent.

'''NOTE: ''' Only configures UART2_TX(6) and UART2_RX(8). You can not use UART2_CTS(4) AND UART2_RTS(10) which are usually referred to as hardware flow control. For example you can use RS232 but not RS485 peripheral. Don't use minicom with hardware flow control enable. '''<br> Go to igep.ini file, replaced by or type this:

<pre>buddy=igep0022

buddy.modem=yes </pre>

= Slow Mode(under construction) Third way =

Slow modeThird way: configure kernel sourcesources.<span lang="en" class="short_text" id="result_box"><span class="hps">Configuration will be</span> <span class="hps">permanent. There are many ways to edit source code, this method is focused for igep0020 RC without igep0022 support.</span></spanbr>

=== Configure IGEP Kernel source code === '''Disable TWL4030 PCM voice interface:'''

Default kernel&nbsp; has disabled TWL4030 PCM voice interface output pins to high impedance, otherwise this module forces the level of mcbsp3_fsx (uart2_rx) and mcbsp3_clkx (uart2_tx) pins. To make sure, go to ~[http://git.isee.biz/?p=pub/scm/linux-omap-2.6.git;a=blob_plain;f=sound/soc/codecs/twl4030.c;hb=linux-2.6.35.y $(kernel path)/sound/soc/codecs/twl4030.c ] file already read: <br>

<pre> 0x04, /* REG_VOICE_IF (0xF) */

</pre>

Make sure that IGEPv2 Expansion '''Disable bluetooth:'''  Go to [http://git.igep.es/?p=pub/scm/linux-omap-2.6.git;a=blob_plain;f=arch/arm/mach-omap2/board-igep0020.c;hb=refs/heads/linux-2.6.35.y $(kernel path)/arch/arm/mach-omap2/board-igep0020.c] and search next line: <pre> else if (hwrev == IGEP2_BOARD_HWREV_C) igep00x0_wifi_bt_init(IGEP2_RC_GPIO_WIFI_NPD, IGEP2_RC_GPIO_WIFI_NRESET, IGEP2_RC_GPIO_BT_NRESET, !opt); </pre> "igep00x0_wifi_bt_init" function initializes WIFI and Bluetooth peripherals. "opt" variable is used for disable Bluetooth in some cases: enabled (opt!=0) or disabled(opt==0). For example you can disable it permanently replacing "opt" by 1: <pre> else if (hwrev == IGEP2_BOARD_HWREV_C) igep00x0_wifi_bt_init(IGEP2_RC_GPIO_WIFI_NPD, go to igep IGEP2_RC_GPIO_WIFI_NRESET, IGEP2_RC_GPIO_BT_NRESET, !1); </pre> '''Disable UART2 default configuration:'''  Search again at the same file: "static struct omap_board_mux board_mux[] __initdata".ini fileRemove the following fields: <pre> OMAP3_MUX(UART2_TX, OMAP_MUX_MODE0 | OMAP_PIN_OUTPUT), OMAP3_MUX(UART2_RX, OMAP_MUX_MODE0 | OMAP_PIN_INPUT), </pre> Add the following fields below: <pre>OMAP3_MUX(UART2_TX, OMAP_MUX_MODE7 | OMAP_PIN_INPUT), OMAP3_MUX(UART2_RX, OMAP_MUX_MODE7 | OMAP_PIN_INPUT), OMAP3_MUX(UART2_RTS, OMAP_MUX_MODE7 | OMAP_PIN_INPUT), OMAP3_MUX(UART2_CTS, OMAP_MUX_MODE7 | OMAP_PIN_INPUT), </pre> '''Enable UART2 in J990:'''  Add the following fields under "OMAP3_MUX(UART2_CTS, OMAP_MUX_MODE7 | OMAP_PIN_INPUT), "&nbsp;:&nbsp;buddy=igep0022 <pre> OMAP3_MUX(MCBSP3_DR, OMAP_MUX_MODE1 | OMAP_PIN_INPUT), OMAP3_MUX(MCBSP3_DX, OMAP_MUX_MODE1 | OMAP_PIN_INPUT), OMAP3_MUX(MCBSP3_FSX, OMAP_MUX_MODE1 | OMAP_PIN_INPUT), OMAP3_MUX(MCBSP3_CLKX, OMAP_MUX_MODE1 | OMAP_PIN_INPUT),</pre> === Compile kernel source code === Use this [[Linux Kernel 2.6.35.y|tutorial]] (Kernel) and this [http://labs.igep.es/index.php/The_IGEP_X-loader other] (IGEPxloader) to install Linaro Headless with your custom kernel in SD card.&nbsp; You can compile the IGEPxloader, but is not necessary.<br> '''Please contributeNOTE:''' for [[Linux_Kernel_2.6.37.y|Kernel 2.6.37.y]] you can use [[How_to_create_a_SD-card_with_the_latest_software_image|this tutorial]] removing default kernel for your new one<br>

= Test UART2 in J990<br> =

<br>

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=== Test ===

 

'''NOTE: '''Starting from Kernel 2.6.37.y, ttySx are named ttyOx.

Connect UART2_TX with UART2_RX. Use minicom to prove UART2 (/dev/ttyS1)&nbsp;:<br>

<pre>minicom -D /dev/ttyS1</pre>

or

<pre>microcom /dev/ttyS1 </pre>

If you write characters and see the echo on the screen, you configure correctly UART.

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 [[Category:CommunicationsUART]] [[Category:How_to_forge]] [[Category:Tutorials]] |}

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