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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/UART UARTUniversal_asynchronous_receiver/transmitter <span style="text-decoration: underline;">here</span>] and [[How to use UARTs|here]].'''<br>'''
There are two 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). '''NOTE: '''UART2 in j990 connector has CMOS voltages (0V-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>
=== Configure IGEP ===
'''Disable Bluetooth:'''
Go to /sys/kernel/debug/omap_mux/<br>
Set sdmmc2_dat5 to gpio137 (mode 4):
<pre>echo 0x004 > sdmmc2_dat5 </pre>
<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 > /sys/class/gpio/gpio137/value</pre>
<pre>root@localhost:/sys/class/gpio# cat /sys/class/gpio/gpio137/value
0
echo 0x007 > uart2_rx
echo 0x007 > uart2_tx </pre>
<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 > mcbsp3_fsx
echo 0x101 > mcbsp3_dr </pre>
<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)
=Second way<br> = Second 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> = Third way = Third way: configure kernel sources. Configuration will be permanent. There are many ways to edit source code, this method is focused for igep0020 RC without igep0022 support.<br> === Configure Kernel source code === '''Disable TWL4030 PCM voice interface:''' Default kernel 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> '''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, 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". Remove 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), " : <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. You can compile the IGEPxloader, but is not necessary.<br> '''NOTE:''' 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> ===
'''UART2 J990 pins:'''
<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) :<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:UART]]