BBB - Connecting up an LCD

RE: BBB - Connecting up an LCD

Former Member — Sat, 14 Jun 2014 13:42:03 GMT

Hi [mention:b0bc65b9ecdc4307bd967592f00e340a:e9ed411860ed4f2ba0265705b8793d05]

I have a question. In your prucode_lcd.p , there is a macro called NSECDEL and MSECDEL . as following:

.macro NSECDEL

MOV r2, 16

NSECDEL1:

SUB r2, r2, 1

QBNE NSECDEL1, r2, 0

.endm

In the comment, it says this makes a 40 nsec delay. But shouldn't there be 32 clock cycles (160nsec) including QNBE ? I was thinking if the compiler optimize the loop by removing QBNE instruction with 16 clock cycles (like how gcc optimize for loop), even then, should it be 80nsec delay?

Sincerely,

Nhan

RE: BBB - Connecting up an LCD

Former Member — Wed, 19 Jun 2013 13:29:40 GMT

Hey Man,

it was a good job I have a question about it.

I wonder if I could connect directly a 7" or 10" touchscreen lcd to BBB. I see some providers which sell this but with an extra interface and there are very expensive for me (e.g. $134)

but I prefer to use for example something like the link below:

http://dx.com/p/original-samsung-7-tft-lcd-24-led-back-light-touch-screen-113500

do you think is it possible? can you guide me please about this issue.

with thanks

Mosi

RE: BBB - Connecting up an LCD

bwelsby — Tue, 28 May 2013 08:16:10 GMT

Nice one.

There are 2 PRUs each with 8KB data memory, 8KB instruction memory and 12K shared ram. There should be enough code space to hold some basic graphics primitives. In a former life I designed graphics systems used in industrial displays, before GPUs and such, and I had to write all these from scratch in Z80 assembler. I'll have a see how easy it is to port to PRU assembly.

RE: BBB - Connecting up an LCD

fustini — Tue, 28 May 2013 02:49:42 GMT

Impressive series of blog posts! Can't wait to see what you do next [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-173d2766-00c5-4e6c-8590-b709fa4d216d/contentimage_5F00_1.png:16:16]