DCMI vs LTDC - simple Pinout on STM32F429 Discovery

sawingor · ‎2015-03-31

Posted on March 31, 2015 at 20:32

Hi!

I have a simple yet hard problem.

As is known, the STM32F429I discovery line has on board mainly ili9341 tft lcd.

The job is to work with OV7670 camera through DCMI and with ili9341 through LTDC. But there is problem with pinout function availibility - mainly the PA4 pin. According to

http://www.st.com/st-web-ui/static/active/en/resource/technical/document/user_manual/DM00093903.pdf

(page 22) PA4 pin is physically connected to ''VSYNC'' with ili9341 lcd - OK, no problem. But PA4 pin (according to

http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/DM00071990.pdf

- page 56) as only one in this packet has there ''DCMI_HSYNC'' functionality. So this mean that I can't use DCMI controller and on-board ili9341 lcd at the same time? Separately I have communication with both parts but there is problem to work together because of pins conflict. Please give some hints how to overcome this problem..

http://www.sciencezero.org/index.php?title=STM32F429_Microcontroller

is also nice page to consider pinouts of F429xx discovery line.

#lcd #dcmi #dcmi #dcmi #dcmi #dcmi #stm32f429 #stm32f429 #stm32f429

sawingor · ‎2015-04-08

Posted on April 08, 2015 at 14:06

This is a very important issue, and I can't figure out this problem. Clive1, I noticed that you are the great adviser in this forum - could you give me at least small clue to work with LTDC and DCMI at the same time on board on which work is performed?

waclawek.jan · ‎2015-04-08

Posted on April 08, 2015 at 14:22

From reading the display controller's datasheet it appears to me that it could be used in non-RGB mode with VSYNC disconnected/tied to a static level.

JW

sawingor · ‎2015-04-08

Posted on April 08, 2015 at 14:45

I noticed also this work around. But the 'VSYNC' is physically connected to PA4 and if I want to use DCMI I have to use this port to have 'HSYNC' synchronization, so there cannot be static voltage level.

But I did not work with non RGB configuration with LCD yet (when RGB, the distortions are horrible), so you mobilize me to check if that 'static' level is problematic. Thank you for reply! I'll share the results

sawingor · ‎2015-04-11

Posted on April 11, 2015 at 21:04

According to

http://www.google.pl/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCAQFjAA&url=http://www.displaytech-us.com/sites/default/files/driver-ic-data-sheet/ILI9341_DS_V1.10_20110415.pdf&ei=OG4pVda6NZG0aY-rgYAN&usg=AFQjCNHsgE5AFAePMlh4jxz8fVLPnAU2ew&sig2=dQSaEktxwBEAO8xhU8iYLA&bvm=bv.90491159%2cd.d2s

datasheet there should be possibility to use MCU 8080 Interfaces without VSYNC usage. But there are two things which prevent from use this interface mode.

First - there is no available pins for IM[3:0] on board where we can choose different MCU modes. This make other that RGB interface impossible to use.

Second - in case of usage write sequence must be provided by host processor (according to

http://www.google.pl/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCAQFjAA&url=http://www.displaytech-us.com/sites/default/files/driver-ic-data-sheet/ILI9341_DS_V1.10_20110415.pdf&ei=OG4pVda6NZG0aY-rgYAN&usg=AFQjCNHsgE5AFAePMlh4jxz8fVLPnAU2ew&sig2=dQSaEktxwBEAO8xhU8iYLA&bvm=bv.90491159%2cd.d2s

datasheet - page 28) because the embedded LTDT controller not support CPU interface (only RGB with timing synchronization). It is very essential to not load CPU (or very very lightly) with the image data transfer.

Anyway it seems that there is no option with interface mode diferent than RGB.

So again there is a problem with pin PA4 VSYNC for LCD and HSYNC for DCMI. Any suggestion how to resolve this problem? :( (Or ultimately hit me in the head and tell that there is no possibility on STM32F429I to use parallel dcmi and ltdc data transfer at the same time)

sawingor · ‎2015-04-13

Posted on April 13, 2015 at 12:17

OK.

For now I can't see any solution than to:

1. Cut off trace for lcd and generate manual interrupt (this requires to take off the lcd which I would avoid because this could make very difficult to connect again the wires which could be disconnected (it seems the lcd is glued to the board).

2. Use embedded synchronization in DCMI so that I don't have to use the HSYNC synchronizaton pins.

The second option seems to be very attractive and I would like to use this. But here is the next problem.

The camera OV7670 has the capability of embedded synchronization in code? I've read thorougly the documentation and it seems there is no possibility to do so. (But I take into consideration that there could be some miss from my site which would be very happy for me if however this option would be possible).

I consider to change the camera - But I cannot find any camera with possibility of synchronization in data! Have anybody have some ideas if there are some cameras or how to configure 'OV' series camera to embedded synchronization?

Impatiently waiting for reply. Thanks