take care: inverted DEPolarity at LTDC!!
Options
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content
2014-12-26 4:07 AM
Posted on December 26, 2014 at 13:07
In LTDC_GCR register of LTDC at STM32F429 HSYNC, VSYNC and DE signal polarity may be chosen:
Bit 31 HSPOL: Horizontal Synchronization Polarity
This bit is set and cleared by software. 0: Horizontal Synchronization polarity is active low 1: Horizontal Synchronization polarity is active high Bit 30 VSPOL: Vertical Synchronization Polarity This bit is set and cleared by software. 0: Vertical Synchronization is active low 1: Vertical Synchronization is active high Bit 29 DEPOL: Data Enable Polarity This bit is set and cleared by software. 0: Data Enable polarity is active low 1: Data Enable polarity is active high If you set all 3 bits to 0, then VSYNC an HSYNC signals are ''0'', but DE signal will be ''1''. It's a question of representation: I think the DE signal is ''active'' while sending valuable pixels, and ''not active'' at the time of sync and back/frontporch. ST's representation is different: think of this signal as ''Data Not Valid''. So hltdc.Init.DEPolarity = LTDC_DEPOLARITY_AL; //active low means that DE signal is 1 while valuable pixels are being sent, and 0 when front+backporch and sync signals active.
0 REPLIES 0
