0
edits
Changes
From IGEP - ISEE Wiki
no edit summary
{{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 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 (first way), editing only igep.ini (second way) or editing kernel source and compile it (third way).
'''NOTE: '''UART2 in j990 connector has CMOS voltages (0V-1V8).'''
= Feedback and Contributing =
= First way<br> =
First way: this mode has a 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 ===
If you use a IGEPv2 Expansion Board, don't use modem for this tutorial<br>
'''Disable Bluetooth:'''
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 > sdmmc2_dat5 </pre>
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 > /sys/class/gpio/gpio137/value</pre>
Revise that:
<pre>root@localhost:/sys/class/gpio# cat /sys/class/gpio/gpio137/value
0
echo 0x007 > uart2_rx
echo 0x007 > uart2_tx </pre>
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 > mcbsp3_fsx
echo 0x101 > mcbsp3_dr </pre>
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
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, but this tutorial method is focused for igep0020 RC. Don't use the next params in igep.ini file: <br> buddy=without igep0022 buddysupport.modem=yes<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.igepisee.esbiz/?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>
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 it replacing "opt" by 1:
<pre> else if (hwrev == IGEP2_BOARD_HWREV_C)
igep00x0_wifi_bt_init(IGEP2_RC_GPIO_WIFI_NPD,
'''Disable UART2 default configuration:'''
<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 at the same positionbelow:
<pre> OMAP3_MUX(UART2_TX, OMAP_MUX_MODE7 | OMAP_PIN_INPUT),
OMAP3_MUX(UART2_RX, OMAP_MUX_MODE7 | OMAP_PIN_INPUT),
'''Enable UART2 in J990:'''
<pre> OMAP3_MUX(MCBSP3_DR, OMAP_MUX_MODE1 | OMAP_PIN_INPUT),
OMAP3_MUX(MCBSP3_DX, OMAP_MUX_MODE1 | OMAP_PIN_INPUT),
=== 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> =
<br>
{| cellspacing="1" cellpadding="1" borderwidth="1200" widthborder="2001"
|-
| Pin
=== 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.
{| cellspacing="1" cellpadding="1" width="200" border="1" align="center" width="200"
|-
|
|}
[[Category:Communications]] [[Category:How_to_forge]] [[Category:TutorialsUART]]
