Re: RA8875 display problems with T4.x - a visual study
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Very interesting...
Jack, W8TEE
On Tuesday, March 25, 2025 at 01:25:53 PM EDT, Greg KF5N via groups.io <greg.electricity@...> wrote:
Hi Mark-
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The T41 project has been successful with this device:
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There was a run of a couple hundred kits which used this device between the Teensy 4.1 and the display.
The kits were successful, and if the operation of the display was a problem, we would have heard about it here.
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I have updated the T41 Main board to what I am calling the T41-2.? Here is the schematic, which shows the above
buffer inserted in the SPI bus between the Teensy and the BuyDisplay:
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I did my best to orient the Teensy on the pcb such that the route is as short was possible.? There is a connector and
a short cable.? The clock is upped to the maximum which I believe is 45 MHz.? The operation has been flawless.
Note that the T41 kits have a longer path and yet there are no reported issues.
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Note that there may be an alternative.? The Teensy/Arduino libraries do not expose the GPIO strength and bandwidth settings.
These are claimed to exist on the PJRC Teensy 4.1 web page.
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So it could be a matter of configuring the SPI GPIOs to higher output power and bandwidth.? I did find a discussion of this at
the PJRC forums.? I'm going to look at this problem when I work on the next version of the Main board.? I may insert
jumpers so the board can be built with or without the buffer chip.
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73 Greg KF5N
-- Jack, W8TEE
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jjpurdum