Continue with last blog…

PS: because I am a totally noob of kernel develop, the process is pretty slow 🙂

I only have a little experience on DMA, I2S and sound codec…for SPI part, still a blank paper. This blog must be hard to understand and very few people will read, but the process is pretty fun for me.

For a common vocore2, once it boot up, the SPI control register 0x10000b28 is like this:

root@OpenWrt:/# mem 0x10000b28 bit
31:1 30:1 29:1 28:0 27:0 26:0 25:0 24:0 23:0 22:0 21:0 20:1 19:0 18:0 17:1 16:0 
15:1 14:0 13:0 12:0 11:1 10:0 09:0 08:0 07:1 06:0 05:0 04:0 03:0 02:1 01:0 00:0

Its ninth bit is int_en, I guess that should be enabled.

Then read datasheet(pretty painful for me) page 11/347, we can find:

So SPI interrupt is 11(0x0b)

Let’s check interrupt register, 0x10000270.
For my VoCore2, the result like this:

root@OpenWrt:~# mem 0x10000270 bit
31:1 30:0 29:0 28:0 27:0 26:0 25:0 24:0 23:0 22:1 21:0 20:0 19:0 18:1 17:1 16:0 
15:0 14:1 13:0 12:0 11:0 10:0 09:0 08:0 07:1 06:1 05:0 04:0 03:0 02:0 01:0 00:0 

22 is UART-Lite2, which we used it for debug console.
18 is USB20, so from its name it should be USB2.0.
17 is ESW, from its name it should be ethernet switcher.
14 is SDXC, absolutely for SD card.
07 is GDMA, general DMA, for sound and i2s we use it to boost up speed.
06 is GPIO, so for fast GPIO it should be useful, like trigger button by low to high voltage edge.
11 is SPI, currently the driver is not used, that is what I will going to do.
31 is not there…as I know it is for soft interrupt, once I read code about it, but can not remember where it is.

I have no idea where to start.
Let’s check GDMA driver first, in dts/MT7628AN.dtsi(openwrt source code)

                gdma: gdma@2800 {
                        compatible = "ralink,rt3883-gdma";
                        reg = <0x2800 0x800>;

                        resets = <&rstctrl 14>;
                        reset-names = "dma";

                        interrupt-parent = <&intc>;
                        interrupts = <7>;

                        #dma-cells = <1>;
                        #dma-channels = <16>;
                        #dma-requests = <16>;

                        status = "disabled";
                };

We can find it has intc at <7>, and in its source code, it connects interrupt with this source code. driver/dma/ralink-gdma.c (linux source code)

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	base = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(base))
		return PTR_ERR(base);
	dma_dev->base = base;
	tasklet_init(&dma_dev->task, gdma_dma_tasklet, (unsigned long)dma_dev);

so once the interrupt is triggered, the kernel should call gdma_dma_tasklet.

Next blog I will update the spi driver source code in linux to check if this interrupt works 😉

I start this SPI driver blog because it is pretty useful and it can be a tutorial for kernel develop.

Currently the SPI driver is from mt7621/mt7620, it works well. I think maybe there is someway to improve it? I have done similar to i2c driver, and for myself it is much better than the original one.

Let’s check openwrt spi-mt7621.c first…

static inline int mt7621_spi_wait_till_ready(struct spi_device *spi)
{
	struct mt7621_spi *rs = spidev_to_mt7621_spi(spi);
	int i;

	for (i = 0; i < RALINK_SPI_WAIT_MAX_LOOP; i++) {
		u32 status;

		status = mt7621_spi_read(rs, MT7621_SPI_TRANS);
		if ((status & SPITRANS_BUSY) == 0) {
			return 0;
		}
		cpu_relax();
		udelay(1);
	}

	return -ETIMEDOUT;
}

From this code, means we are using busy wait for every bit. This will consume a lot of CPU time and increase VoCore2 current. Busy wait is never a good idea, but easy to develop.

Check datasheet again, 0x10000b28 bit 9 is Interrupt Enable. That means we might have a way avoid busy wait, even more, we might have a way to use DMA for mass data transfer.

Tomorrow I will try to make some test. I can directly write to SPI register in user space by mmap.

To be continue...

VoCore2 Ultimate and its USB screen.

My USB screen is a standard framebuffer device, and VoCore2 is a standard linux device, so showing something from console to the screen is simple.

Prepare Firmware

Compile your own firmware or download my compiled firmware at vonger.cn/misc/screen/20190828.bin. The driver name is fbusb, I have submitted its source code to github.com/vonger, feel free to submit patch.

PS: The driver supports different driver chip(must be 8080 interface), currently we support ili9806g for the screen back marked ‘vocore2’, another one is based on nt35510, back mark is ‘djn1522’. Their driver board is same but pin order is different, and for later screen we will only use the version based on nt35510.

PSS: Both of the screens support 24bit color in Windows Bitmap format, unfortunately, Linux driver do not support that yet, it only support 8/16/32 bit color and 24bit color is not taken 3 bytes, it takes 4bytes…because of this small issue, we have to modify linux framebuffer code to support 24bit color, but that is pretty complex, I did not done yet(use libusb send the 24bit data is a better way).

OK, now let’s back to topic. To enable the driver, just download fbusb to openwrt packages folder and in “make menuconfig” select VoCore2 -> (M)fbusb.

After compile, you will have fbusb.ko.

We also need to modify VOCORE2.dtsi in openwrt source code at target/linux/ramips/dts/, set bootargs to bootargs = “console=ttyS2,115200 console=tty0 fbcon=rotate:3”; , this means show console both on ttyS2 which is our debug serial port and tty0 which is the screen framebuffer console. rotate:3 is used to rotate the screen position, default it is vertical.

Upgrade VoCore2

Copy the firmware to VoCore2 and use sysupgrade flash it or just use LuCI interface system upgrade…This tutorial also at vocore.io/v2u.html

Connect screen to it and reboot. Then around 10 seconds, you will find the console as the title picture. If you want some input, connect one USB hub and one USB keyboard. 🙂

Now we have a kicad version hardware source. 🙂 It should help to layout customized dock board.

Download at vocore.io/v2.html, Sources/Hardware section.

Currently VoCore2 do not have reset button, so some beginners are hard to reset the firmware once it is bricked by wrong setting…

This new patch of uboot is used to solve that, it is much easier than upload firmware from serial port, but maybe still hard for beginner.

If you want to have a try of the new uboot, please download from vonger.cn/misc/vocore2/uboot128m.20190808.bin (Lite version please use uboot64m.20190808.bin, or it will failed to boot).

You can use exists uboot on vocore, choose 7 to upload new uboot to VoCore2 by serial port(kermit protocol)

To active first boot from uboot, you need to connect I2C_SD pin(GPIO5) to GND then power on your VoCore2. Another way is in uboot menu, press ‘r’, then it will reset firmware automatically, this way need serial port, not that simple like first way.

VoCore2 wifi LED will flash quickly (0.07s/0.1s), means you have entry reset mode, then disconnect I2C_SD pin from GND, the flash speed will slow down(1s/1s), that means we are erasing the NOR flash. Around 3 minutes, it stops flashing, the reset is done.

Here is the patch(modify board.c only), you can download full patch from https://github.com/Vonger/uboot/blob/master/uboot-20190808.patch

How it works?

I2C_SD pin has a pull-up resistor, so we can use it as a ‘button’.

1. once boot up, uboot will set I2C_SD into GPIO input mode and check its value. If it is 1, means we should boot normally, button is not pressed; if it is 0, means ‘button’ is pressed, we should go to reset mode.
2. in reset mode, we flash the wifi led quickly to notify user we are ready to reset. Once user disconnect I2C_SD to GND (release the button), we are ready to erase the flash.
3. We need to keep firmware just reset user data, and user data is in rootfs_data partition. So in order to find the partition position, we have to use a tricky, because rootfs_data is jffs2 disk format, we just need to find its magic code at every 0x10000 bytes. Once we find its start position, we can easily use SPI command to erase the flash rootfs_data.
4. finally, start linux. It will do rest. 🙂

I get a cheap 4G modem recently. Very interesting, my BOM cost of such thing will be over 150CNY(consider mass production 10K), but the provider of the 4G modem sell it only 100CNY and provide 6GB free data usage…

The modem is based on MDM9600 from Qualcomm which is well known since 2012.

PS: now I know the low cost secret 🙂 all recycle chips…kind of environmentalist?

Let me explain how to make it work with VoCore2.

Prepare Firmware

First need to add kmod-usb-serial to firmware, old version of vocore2 firmware do not have it inside, you need to recompile your firmware and put the driver inside…it can not be install from opkg update. Or use later than 20190802 version firmware, I have embed it into firmware.

It is in make menuconfig -> Kernel modules -> USB Support -> (* or M)kmod-usb-serial

After this, we can upload the firmware to vocore2 and use opkg install other necessary packages(or you can directly compile them from source)

opkg update
opkg install usb-modeswitch usbutils

Install these packages should be enough, but in order to make it easier, we can also install luci-proto-3g, so we can setup in luci web interface.

Once we plugin the USB 4G modem to vocore2 usb port, new device will show when you call lsusb:

Bus 001 Device 003: ID 05c6:92fe Qualcomm, Inc

This is not the real modem, just a virtual usb disk, we need to use usbmode to switch it into modem mode.

openwrt provided usb-modeswitch can do this, but it do not have my 4G modem USB VID/PID which is 05c6:92fe.

I have to patch /etc/usbmode.json in vocore2. add config to its line 453, right after 05c6:9024

"05c6:92fe": {                                                  
                        "*": {                                                  
                                "t_vendor": 1478,                               
                                "t_product": [ 36901 ],                         
                                "mode": "StandardEject",                        
                                "msg": [  ]                                     
                        }
             },       

PS: just eject the disk then the mode changes…simple.

and then call “usbmode -s”, the USB disk now switch to real LTE modem.

now call lsusb, you will find a new device:

Bus 001 Device 003: ID 05c6:9201 Qualcomm, Inc. Gobi Wireless Modem (QDL mode)

and in /dev/ folder, you will find ttyUSB0, ttyUSB1, ttyUSB2, ttyUSB3.

note: use command comgt -d /dev/ttyUSBx to check which ttyUSB is usable, mine is ttyUSB1

setup usbserial driver to this device:

usbserial is load at startup.

echo "usbserial vendor=0x05c6 product=0x9201" > /etc/modules.d/usb-serial

Or call insmod with parameters.

Now after reboot, it is ready to use.

Setup Network

For simple, just use luci, in Network -> Interfaces, click on “Add Interface”

Then “Submit”

note: APN and dial number might be different for different service providers.

Finally, update the firewall:

Then click “Save and Apply”, you can access to internet by 4G now 🙂

Or we can do it in a HARD way, do it in console.

add config to /etc/config/network.

config interface 'lte'
   option proto '3g'
   option device '/dev/ttyUSB1'
   option service 'umts'
   option apn '3gnet'
   option dialnumber '*99#'
   option ipv6 'auto'

add config to /etc/config/firewall

config zone
	option name 'wan'
	list network 'wan'
	list network 'wan6'
	list network 'wwan'
	list network 'lte'
	option output 'ACCEPT'
	option forward 'REJECT'
	option masq '1'
	option mtu_fix '1'
	option input 'ACCEPT'

manually run to start ppp diag…(I am lazy, did not test this, might not work) or just simply call /etc/init.d/network restart

/usr/sbin/pppd nodetach ipparam lte ifname 3g-lte lcp-echo-interval 1 lcp-echo-failure 5 lcp-echo-adaptiv

after that you can find it in your ifconfig.

3g-lte Link encap:Point-to-Point Protocol
 inet addr:10.14.231.24 P-t-P:10.64.64.64 Mask:255.255.255.255
 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1
 RX packets:408 errors:0 dropped:0 overruns:0 frame:0
 TX packets:474 errors:0 dropped:0 overruns:0 carrier:0
 collisions:0 txqueuelen:3
 RX bytes:148233 (144.7 KiB) TX bytes:79615 (77.7 KiB)

And now you can access internet once connect to VoCore2 hotspot.

PS: I find a bug, after reboot, pppd service will start but after around 10 seconds, it disappears. Look like some network process killed it.

Have to change the /etc/config/network, ttyUSB1 change to ttyUSB2(or USB2 to USB1) and restart network after boot up ready.

It has been three years, I still can not forget this project…It must be true love.

Currently USB screen are using two version of power supply chip, one is SY7200AABC, another is PT4103.

I thought they should be same function and work in same way…but I am wrong. PT4103 backlight is not as bright as SY7200AABC.

There is something wrong about PT4103…I set its current to 40mA, but the voltage on backlight is only 11.3V~11.5V, far from the required voltage 12.8V(3.2V x 4), but SY7200AABC works well, it is able to reach 12.5V.

First I think it is my design problem, maybe my resistors and inductors are wrong, but I tried modify the feedback resistor from 2ohm to 10ohm and change the inductor from 10uH~47uH, still no acceptable result. I find even I setup feedback resistor to 2ohm, the voltage is still lower than 11.5V.

I have no idea why PowTech’s PT4103 does not work, it should be a widely used chip but it is not as stable as SY7200AABC. Later version screen driver board I will use SY7200AABC.

Finally I get its documentation about XU registers, that means we can use its extend features now.
It supports OSD(the text on the picture, such as time or gps data), SEI(the data directly embed into the video stream, can be text or anything), motion detect (find bad guy), GPIO(not used) etc…

From my test, h264 at 25fps, 1080p, 14Mbps frame rate, power consume is 1.1w, not very low but much better than other h264 camera.
If for secure monitor or similar usage, at 5fps, 1080p is only 0.7watt.

PS: new demo and its source code example has upload to https://vocore.io/camera.html

Simple DEMO Usage:

1. Record 10 seconds(25fps, 250 frames) video stream into h264 file(RecordH264.h264).
note: Copy TestAP to /tmp or SD card folder, make sure the folder has at least 20MB free space.
./TestAP /dev/video1 –format H264 –size 1920×1080 –record –capture=250 –fr 25

2. Set H264 bitrate to 4Mbps.
./TestAP /dev/video1 –xuset-br 4000000

PS: its log will show XU_Multi_Get_Enable failed, ignore that, it should be something this camera do not support, once you find XU_H264_Set_BitRate <== Success, it is success.

This demo code is pretty bad but works…Later I will try to clean up the code and make a new demo.

This is just the first step…

PS: take by crap phone camera, not screen capture, sorry about the bad image quality.

I find last time I can not insmod fbusb.ko to raspberry pi is because a stupid issue…raspberry pi already have a module named usbtest.ko, it is using same USB VID/PID. Ye, I can not afford that USB ID cost so I just use the chip CY7C680 default VID/PID, that cause the conflict and kernel taint… 🙂

Now it works…just replace the usbtest.ko in /lib/modules/4.19.50*/kernel/drivers/usb/misc/usbtest.ko with fbusb.xxxx.ko, in /lib/modules there are three usbtest.ko, not sure why there are so many of them…for simple, replace them all 🙂

Then reboot, you will find /dev/fb1, and write 16bit bmp to it, display normal.
It’s done. :p

PS: sudo FRAMEBUFFER=/dev/fb1 startx do not work..need deep dig into it.