Making 3rd party Mesa daughter card: what are the voltage levels?
29 Aug 2024 16:43 #308953
by mkudlacek
Like many of us, apparently, I ran out of IO's on my Mesa 7i96s as my CNC project got bigger. I'm in EU (Czech Republic) and I cannot find daughter card in nearby eshops, that is in stock and doesn't cost arm, leg and/or kidney. I'm cheeky enough to think that I can wire a simple IO card by myself.
The question is: what are the voltage levels of the IOs on the IDC26 connector? I see someone connecting a parallel BOB directly, so is it 5V, or 3.3V since it is wired to the FPGA?
Thanks for info,
Martin
PS: If everything goes well with prototyping, I will make a custom PCB. Anyone else interested?
The question is: what are the voltage levels of the IOs on the IDC26 connector? I see someone connecting a parallel BOB directly, so is it 5V, or 3.3V since it is wired to the FPGA?
Thanks for info,
Martin
PS: If everything goes well with prototyping, I will make a custom PCB. Anyone else interested?
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29 Aug 2024 17:10 - 29 Aug 2024 17:20 #308955
by PCW
Replied by PCW on topic Making 3rd party Mesa daughter card: what are the voltage levels?
7I96 P1 voltage levels are basically 3.3V though
you can get 5V output swing using open drain
output mode. (all I/O have 4.7K pullups to 5V)
Daughtercard design need to consider that all
P1 I/O will be high at startup because of these pullups
All I/O pins are 5V tolerant.
Input thresholds are LVTTL so approximately 1.5V
Maximum input voltage is +7V
Minimum input voltage is -0.5V
Maximum source/sink current is 16 mA
(more negative than -0.5V without current limiting
will damage the input clamp diodes = 10 mA Max)
Also note that you can get power for your daughtercard
via P1
you can get 5V output swing using open drain
output mode. (all I/O have 4.7K pullups to 5V)
Daughtercard design need to consider that all
P1 I/O will be high at startup because of these pullups
All I/O pins are 5V tolerant.
Input thresholds are LVTTL so approximately 1.5V
Maximum input voltage is +7V
Minimum input voltage is -0.5V
Maximum source/sink current is 16 mA
(more negative than -0.5V without current limiting
will damage the input clamp diodes = 10 mA Max)
Also note that you can get power for your daughtercard
via P1
Last edit: 29 Aug 2024 17:20 by PCW.
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29 Aug 2024 17:20 #308956
by tommylight
Replied by tommylight on topic Making 3rd party Mesa daughter card: what are the voltage levels?
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29 Aug 2024 18:07 #308961
by mkudlacek
Replied by mkudlacek on topic Making 3rd party Mesa daughter card: what are the voltage levels?
Thank you both of you. I've sifted through the manual for days, not finding this page. Shame on me.
I'm going to cobble together a simple 4-16 input card, because inputs are what I ran out. There will be optocoupler protection, maybe even input protection on the IDC26 side just like on the full fledged card. And some LED indication, possibly wrapped in some enclosure.
@PCW As I understand from other posts, you are a HW developer of the Mesa, is that correct? What is your (or the company's) stance on me building/sharing this and maybe selling as a 3rd party card? From my brief encounter with you and this wonderful community here, I wouldn't like to step outside of some boundaries, but rather give back in form of something, that isn't readily available via main channel. Thank you for answer in advance.
Have nice day,
Martin
I'm going to cobble together a simple 4-16 input card, because inputs are what I ran out. There will be optocoupler protection, maybe even input protection on the IDC26 side just like on the full fledged card. And some LED indication, possibly wrapped in some enclosure.
@PCW As I understand from other posts, you are a HW developer of the Mesa, is that correct? What is your (or the company's) stance on me building/sharing this and maybe selling as a 3rd party card? From my brief encounter with you and this wonderful community here, I wouldn't like to step outside of some boundaries, but rather give back in form of something, that isn't readily available via main channel. Thank you for answer in advance.
Have nice day,
Martin
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29 Aug 2024 18:23 - 30 Aug 2024 00:27 #308963
by PCW
Replied by PCW on topic Making 3rd party Mesa daughter card: what are the voltage levels?
I certainly don't have (or even could have) any objections to you making a compatible
daughtercard (or even main card since the hostmot2 firmware is all open source)
My only suggestion would be make sure that your daughtercard is general enough
that it works with other similar interfaces (Parallel, RIO, etc)
daughtercard (or even main card since the hostmot2 firmware is all open source)
My only suggestion would be make sure that your daughtercard is general enough
that it works with other similar interfaces (Parallel, RIO, etc)
Last edit: 30 Aug 2024 00:27 by PCW.
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29 Aug 2024 22:43 #308986
by cornholio
Replied by cornholio on topic Making 3rd party Mesa daughter card: what are the voltage levels?
Did you mean to say you don't have ?
Or am I misunderstanding ?
Either way Pete your very very gracious with your time, even for those of us who experiment with your firmware on other hardware.
Or am I misunderstanding ?
Either way Pete your very very gracious with your time, even for those of us who experiment with your firmware on other hardware.
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30 Aug 2024 00:28 #308995
by PCW
Replied by PCW on topic Making 3rd party Mesa daughter card: what are the voltage levels?
sorry I left out the "don't"
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