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Forum Index : Microcontroller and PC projects : E100 - Pullups on Keyboard?
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9750 |
Hello all.  I have had a question from someone asking about possible noise on the KB lines causing odd things to happen with their E100. The problem seems to have been solved by adding 4k7 pull-up resistors on the KB clock and data lines. In the schematic, they are not shown and these two lines are floating, and I am just wondering if those resistors are actually supposed to be there but were perhaps missed on the schematic? Geoff? Specifically, the piezo beeper used for touch clicks was squealing intermittently when it should not have been. Apparently, fitting the pull-ups to the KB lines has stopped it on the one I know about - so far. Has anyone here who has got an E100 from me, WhiteWizzard or Silicon Chip ever had any problems with the piezo squeaking when it should not, when you have a keyboard connected to the board? I myself have never heard of this, but it must be able to happen if someone is reporting it. At this stage, for the next revision of the board, I plan to include 4k7 pull-ups on the KB lines a-la the I2C pull-ups. I note that page 40 of the Micromite Plus manual DOES show 4k7 resistors, but the E100 schematic(V4) does NOT show them..... EDIT: My contact tells me this happens with the KB NOT plugged in. Just touch around the KB socket area, and the piezo squeaks. Very odd. Would LOVE to hear from any member who has had this happen to them. Smoke makes things work. When the smoke gets out, it stops! |
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Geoffg Guru  Joined: 06/06/2011 Location: AustraliaPosts: 3308 |
I have not seen that and I have used the E100 a lot with a keyboard. I put pullups into the original Maximite (if my memory is correct) but then I found that all keyboards had their own pullups built in - so I dropped them for the E100. Weak pullups can be enabled in the PIC32. I will build a special version for your fellow to test. Geoff Geoff Graham - http://geoffg.net |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9750 |
Hi Geoff. Could he perhaps make use of the ChangePin Cfunction to enable the pullups on the existing firmware? Smoke makes things work. When the smoke gets out, it stops! |
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| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 655 |
G'Day Geof But what happens when the KB is unplugged? |
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| Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3308 |
Yes, much easier. It occurred to me that he has probably soldered in the pullups so there is no point building a test version anyway. The internal PIC32 pullups will pull the signal lines high (which is the inactive state). Geoff Geoff Graham - http://geoffg.net |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9750 |
I believe he has soldered in the 4k7's for now to settle things down. Perhaps if he removes the 4k7's and runs the ChangePin Cfunction on both of the keyboard pins? Smoke makes things work. When the smoke gets out, it stops! |
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| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 655 |
G'Day Geof But what happens when the KB is unplugged? G'Day Geof. But there are no pullups. But there will be:) Peter |
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