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wuxx / icesugar

iCESugar FPGA Board (base on iCE40UP5k)
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What is the purpose of J7? #22

Closed umarcor closed 3 years ago

umarcor commented 3 years ago

Comparing the schematics of v1.4 and v1.5, I found the difference to be the addition of J7, which seems to duplicate 4 of the pins in PMOD1:

iCESugar-v1 4_to_v1 5

The render and photo of v1.0 and v1.3, respectively, show that J7 was not there before. Comparing to a photo of v1.5 it looks like the distance between PMOD2 and PMOD3 was increased.

My understanding is that J7 was added for PMOD-RGBLCD, which has 30 pins (2x15). Hence a female angled 2x3P connector such as the following needs to be soldered in J7 for using PMOD-RGBLCD:

A2541HWR-2x3P

I assume that the spacing between PMOD connectors in PMOD-VGA and PMOD-TFTLCD matches the "new" separation in the v1.5 board design, and not the previous. With regard to the PMOD specification it seems that v1.5 complies with the separation between PMODs (22.86mm or 0.90"). Therefore, "standard" peripherals with two PMODs can be connected to the ICESugar now. Say, Pmod SSD or Pmod motor driver. By the same token, the PMOD-VGA and PMOD-TFTLCD of Muse Lab Factory Store can be used with any other board providing two properly spaced PMODs. Is this correct?

wuxx commented 3 years ago

yes, the distance of v1.5 is obey the specification, you can use other standard PMOD peripherals. and the J7 is expose 4 more GPIO and 5V power supply, it's suit for PMOD-RGBLCD with rgb565 color. a bad news: you can not solder the 2x3P connector between two 2x6P pmod, it will get stuck. so when somebody buy the pmod-rgblcd, we will send board with 2x15p connector like this. icesugar-pmod

umarcor commented 3 years ago

Thanks! That makes sense...

Does the PMOD-RGBLCD module depend on some of the signals in the 2x15 connector being differential pairs? Or are all pins used as general purpose I/O?

It seems that the 5V in the RGBLCD are used for the backlight only. I.e., all signals are 3V3. Is that correct?

wuxx commented 3 years ago

yes, the more 4 IO is perfect for rgb lcd with rgb565, check this demo for the detail https://github.com/wuxx/icesugar/tree/master/src/basic/verilog/rgblcd 5V for the backlight (boost to about 18V), the IO is 3.3V.