Question about custom BOB for a 7i92
29 Apr 2023 23:50 - 29 Apr 2023 23:52 #270266
by blazini36
Also thinking of multiplexing the outputs so I can squeeze 2 more stepgens in there for rev2. I only see "OutM" in the hostmot2 docs, I assume that's an output mux that I can use a multiplexer with 3 address lines and a direction line with like inMux? Can the FPGA handle 8 stepgens along with the rest of what I stuffed in there?.
That first pinout still relates to the PCB I have on the way so that's the actual firmware I need for now (with the frame pin on CS_A1 as you suggested).
Replied by blazini36 on topic Question about custom BOB for a 7i92
I was planning on using an on-board jumper to enable all buffers as well as the buffering the external CS (maybe not necessary with the decoder output), so basically the connector is dead unless the jumper is on and presumably not being instantiated via the component.....or is there some issue with the MISO buffer being on when the external chip is not selected via CS?Yes, you could add an external SPI port
Note that if you buffer MISO you need to
enable the buffer with the chip select
(and that buffering will slow things down a bit)
Also thinking of multiplexing the outputs so I can squeeze 2 more stepgens in there for rev2. I only see "OutM" in the hostmot2 docs, I assume that's an output mux that I can use a multiplexer with 3 address lines and a direction line with like inMux? Can the FPGA handle 8 stepgens along with the rest of what I stuffed in there?.
That first pinout still relates to the PCB I have on the way so that's the actual firmware I need for now (with the frame pin on CS_A1 as you suggested).
Last edit: 29 Apr 2023 23:52 by blazini36.
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30 Apr 2023 00:31 #270271
by PCW
Replied by PCW on topic Question about custom BOB for a 7i92
There is no muxed output module currently So I would not count on that
(If i do this eventually I would use a shift register like the 74HCT595)
(If i do this eventually I would use a shift register like the 74HCT595)
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30 Apr 2023 02:03 - 30 Apr 2023 02:22 #270273
by blazini36
Replied by blazini36 on topic Question about custom BOB for a 7i92
Have to figure out whether I want to ditch SS or not then, starting to ask alot of that little board.
I'm not terribly familiar with decoders, multiplexers or SPI in general but this is what I'm looking at.
Edit, Edit,
Had to look at it about three times to understand the issue. I suppose the issue is the buffer overcoming the MISO line cancelling out the other devices on the line?
BTW, appreciate the help.....didn't expect it to get this complicated.
I'm not terribly familiar with decoders, multiplexers or SPI in general but this is what I'm looking at.
Edit, Edit,
Had to look at it about three times to understand the issue. I suppose the issue is the buffer overcoming the MISO line cancelling out the other devices on the line?
BTW, appreciate the help.....didn't expect it to get this complicated.
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Last edit: 30 Apr 2023 02:22 by blazini36.
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30 Apr 2023 02:48 #270281
by blazini36
Replied by blazini36 on topic Question about custom BOB for a 7i92
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01 May 2023 03:31 - 01 May 2023 03:34 #270374
by PCW
Replied by PCW on topic Question about custom BOB for a 7i92
Note that you could use a '125 (active low enables)
instead of the '126 to eliminate the inverter
Also you have the input/output swapped on the buffers MISO signal
instead of the '126 to eliminate the inverter
Also you have the input/output swapped on the buffers MISO signal
Last edit: 01 May 2023 03:34 by PCW.
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01 May 2023 03:47 #270375
by blazini36
good call on the '125 chip, I'll have to find some kind of resource for common ICs and their differences, like active low enables.
Replied by blazini36 on topic Question about custom BOB for a 7i92
Good catch, I just threw that together quick so I could try to understand the issue with the MISO buffer you mentioned and that symbol wasn't in the library.Note that you could use a '125 (active low enables)
instead of the '126 to eliminate the inverter
Also you have the input/output swapped on the buffers MISO signal
good call on the '125 chip, I'll have to find some kind of resource for common ICs and their differences, like active low enables.
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01 May 2023 04:07 #270376
by blazini36
Replied by blazini36 on topic Question about custom BOB for a 7i92
Also, I don't know if bspi is using active high or low to enable the decoder. I have the active high in use on that sheet. I'm planning to use the pull down jumper on both headers if that matters.
I'm also using the non-inverted output of the HC251 chip assuming that's what InMux is looking for, is that correct?
I'm also using the non-inverted output of the HC251 chip assuming that's what InMux is looking for, is that correct?
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01 May 2023 13:49 #270409
by PCW
Replied by PCW on topic Question about custom BOB for a 7i92
I think the frame default is active low
(though can be inverted in the hal file)
On the 251 I would use the inverted output
as the default is also active low
(though can be inverted in the hal file)
On the 251 I would use the inverted output
as the default is also active low
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04 May 2023 17:10 #270648
by blazini36
Replied by blazini36 on topic Question about custom BOB for a 7i92
PCW, any word on that firmware?
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04 May 2023 17:51 #270655
by PCW
Replied by PCW on topic Question about custom BOB for a 7i92
Do you have a final pinout?
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