STM32F746G-DISCO display panel choice and alternatives

[ray23]

Posted on January 16, 2017 at 18:53

I bought a STM32F746G-DISCO board and have decided that a board like it will fit the needs of my project. Are there any companies that make development boards with this MCU that can use a larger LCD display? The disco board has a 40 pin RGB interface with the touch pins combined within the 40 pins and I can't seem to find a larger LCD panel that has this connector. Do any companies make other boards for this MCU?

#stm32f7 Note: this post was migrated and contained many threaded conversations, some content may be missing.

[ray23]

Posted on January 19, 2017 at 19:28

I want to make sure I understand what this is.

I purchase this board which has a 4'LCD panel. I jettison the panel and buy the 

MIPI-DSI to HDMI board.  I will look at the documentation to see how they connect, if I need to build a circuit for this, it may be a problem.  Then any reasonable HDMI interface display can be used.  

The question is, Can I use the BSP graphics to talk to this display?  Or is another driver required?  Is the driver provided with the MIPI-DSI card support.   I will of course look all of this up.

[ray23]

Posted on January 19, 2017 at 19:30

Does the MIPI-DSI support touch input?  I will be looking this up as well.

[Matej Zub?i?]

Posted on January 19, 2017 at 19:43

If you follow Clive's link to the thread about Rocktech's panel, you'll see that it was a custom job. I assume that STM required a capacitive touch panel with an integrated controller. Smaller panels like those usually come with resistive touch panels.

What would you like to communicate to them? What is your need?

If you want to make a product and need a display, you could contact them. If you need one-off, don't bother.

Without making some type of an adapter, you'll not be able to interface displays >7'. Larger displays usually have more backlight LEDs and have different pinouts. But, if you would like a 5' display (800x480) here is one HSD050IDW1-Axx. It can be purchased for 11$ on

https://www.aliexpress.com/item/HSD050IDW1-A20-A10A30-GPS-UMPC-5-inch-HD-LCD-screen-Portable-navigation-With-touch-screen/32614731060.html?ws_ab_test=searchweb0_0,searchweb201602_1_10065_10068_10000009_10000032_10084_10000025_10083_10080_10000029_10082_10081_10000028_10110_10111_10112_10060_10113_10...

. It is a 'drop in' (you would have to solder it in) replacement with resistive touch panel (that would not work with the existing discovery).

[Matej Zub?i?]

Posted on January 19, 2017 at 20:10

nefarious wrote:

I purchase this board which has a 4'LCD panel. I jettison the panel and buy the 

MIPI-DSI to HDMI board.  I will look at the documentation to see how they connect, if I need to build a circuit for this, it may be a problem.  Then any reasonable HDMI interface display can be used.

You can purchase that discovery board without LCD (

http://www.digikey.com/product-detail/en/stmicroelectronics/STM32F769I-DISC1/497-16712-ND/6193103

). Make a search for STM32F769I-DISC1 (the MFG code) at your distributors and you'll get results without the LCD. Discovery and MIPI2HDMI bridge interconnect through a connector already present on both boards, i.e. plug and play.

The question is, Can I use the BSP graphics to talk to this display?  Or is another driver required?  Is the driver provided with the MIPI-DSI card support.   I will of course look all of this up.

You would have to check the intricacies, but you already have code for MIPI-DSI as part of the BSP. Look for the ADV7533 (DSI-HDMI bridge) in BSP and see if there are any examples.

[Matej Zub?i?]

Posted on January 19, 2017 at 20:16

MIPI-DSI is video standard (Display Serial Interface), no touch interface as part of it. You have to handle that by yourself.

Some panels will have a touch option. Go for capacitive touch panel with an integrated controller to which you can speak using I2C.

When you use MIPI2HDMI you'll 'get' audio

[ray23]

Posted on January 19, 2017 at 20:29

I looked at the device on Aliexpress, yes it is $11 but with shipping it is $46.  Not that that is too much.  

I tried to see if I could find the pinout of the panel and it is not available, also I looked to see if I could find what touch panel it had, capacitive vs resistive and could not find that reference.  I have looked a many 40 pin RGB connectors and none of them have had the touch panel pins on the flex cable connector correctly.

[Matej Zub?i?]

Posted on January 19, 2017 at 21:40

That is too much Search for the

HSD050IDW1.

I attached the datasheet. This LCD doesn't have a controller, so you would have to constantly refresh the display.

You can take a look at the LTDC LCD peripheral in

http://www.st.com/content/ccc/resource/technical/document/reference_manual/c5/cf/ef/52/c0/f1/4b/fa/DM001248pdf/files/DM001248pdf/jcr:content/translations/en.DM001248pdf

for STM32F7 series, or

http://www.st.com/content/ccc/resource/training/technical/product_training/group0/3f/7b/af/97/88/ba/48/33/STM32F7_Peripheral_LTDC/files/STM32F7_Peripheral_LTDC.pdf/_jcr_content/translations/en.STM32F7_Peripheral_LTDC.pdf

short presentation. Max. resolution for direct drive of a LCD panel is 1024x768 24bit.

The HSD050IDW1 display has either no touch panel or a resistive one. If it is a resistive one, there is a thin sheet over the LCD with 4 connections. To make sense of these signals you need a resistive touch screen controller. Btw. It'snot present on the Discovery board. So either you'll have a capacitive one with correct pinout or no touch. I think we'll not find correct orientation of the capacitive controller pins due to custom nature of the display (from the Discovery board) build.

I have looked a many 40 pin RGB connectors and none of them have had the touch panel pins on the flex cable connector correctly.

Yes. I've also seen some LCDs with capacitive touch screen, but all of them have 'wrong' pinout in contrast to those found on the Discovery board.

________________ Attachments : HSD050IDW1-Axx.pdf : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HyzJ&d=%2Fa%2F0X0000000bEt%2FdqlOZSbVfHBGv98XevOpvR52nPT7v.axSgWmlAJr3dI&asPdf=false

[ray23]

Posted on January 19, 2017 at 22:50

I find it remarkable that stm would implement this solution this way.  If you look at the stm32F7691-DISCO it shows as having 

• 4' capacitive touch LCD display with MIPI® DSI connector (on STM32F769I-DISCO only)

and this is provided with this option B-LCD40-DSI1 which connects to the motherboard with the MIPI_DSI interface.  Then look at the connector to the motherboard and it has i2c on pins 40 and 44 which is how the touch screen is passed to the motherboard for processing.  So, the 

STM32F769I supports capacitive touch over I2C.

The question is then, why would they not put a 4 pin connector on the B-LCDAD-HDMI1 to allow the signals from the touch panel to be passed to the motherboard in the same way as the 4 inch touch panel?

[richard239955_stm1]

Posted on January 20, 2017 at 01:35

I'm going to reply to myself to inform folks that so far, all the suppliers we've dealt with have graciously provided schematic and PCB information. Many of them appear to use Altium.

[Matej Zub?i?]

Posted on January 20, 2017 at 12:08

It is not common to have a HDMI display with a touch panel. So, STM engineers assumed only video (and audio) out on that connector. But, if a panel that you might buy has a capacitive touch panel. It will most certainly have available pins to which you can interface. Using bare wires to connect them to the I2C pins on the 'Arduino' header found on the STM32F769 discovery (p. 22, sect. 7.2). On that header, there are other pins available if you are going to use interrupts or to control something.

I know that there has been a lot of informations here and that it does take some time to find the appropriate solution. That is why I would like to invite you to change the name of this thread. To something like 'STM32F746G-DISCO display panel choice and alternatives'. Since we have broadened this discussion from 'STM32F746NG MCU boards'.