PDA keyboards

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Anyone know if there is a standard keyboard interface/protocol used for PDAs?

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Most modern Windows for Mobile Devices PDAs support bluetooth keyboards, and possibly IR ones, via a driver.

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Thanks, I was thinking more along the lines of the hardwired connections. I was looking at a couple that had a fold up hard case that would be convenient to throw in the toolbox. I have a lot of our machines that use a touch screen as the primary operator interface but sometimes when servicing them I need to drop down to a command prompt to do some low level reconfigurations in which case I need to attach a real ps2 keyboard. I was also thinking that they might make a good alternative input device to regular matrix keypads for use with some AVR projects.

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I decided to order one of these to play with. It apears to just use a standard serial interface. I'm surprised others have not made use of these before?

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I have and the one you showed is my favorite. You can fit a lot of electronics inside the hole where the pda would normally go. One question though. On mine if found the tx signal was TTL but inverted compared to the normal TTL RS232. Did you have the same experience?

Oh the great thing about all these keyboards is you can get them on ebay for almost nothing.

Go electric!
Happy electric car owner / builder

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sgomes wrote:
I have and the one you showed is my favorite. You can fit a lot of electronics inside the hole where the pda would normally go. One question though. On mine if found the tx signal was TTL but inverted compared to the normal TTL RS232. Did you have the same experience?

Oh the great thing about all these keyboards is you can get them on ebay for almost nothing.

I'm still waiting on delivery, probably another day or two. I ordered the above unit new from ioffer.com for 4.50 + 3.00 s/h so yeah the price is right :)

I'll post my findings as soon as I get it.

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If you need it I can find my text file of all the key codes. It might save you some time.

Go electric!
Happy electric car owner / builder

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sgomes wrote:
If you need it I can find my text file of all the key codes. It might save you some time.

Well, I finally got my ThumbBoard. I did an initial translation of the pinout but I don't seem to be getting a signal yet.

Looking at the soldered terminals L -> R I get:

1 - Cts
2 - Detect
3 - TxD
4 - Vin 3.2V
5 - ID
6 - Sig Gnd
7 - Hotsync
8 - Gnd

According to the pinout I found on the PALM505 the serial port uses standard rs232 voltage levels which makes me think it might be using the voltage from the PALM rts to derive the voltage level for transmit.

If you or anyone else is able to verify any of this I would appreciate it.

Thanks

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I'm not sure about all those signals. I can't find my original notebook. However, I can tell you that I applied 3.3V to pins 2 and 4. Then I looked for signals coming out of pin 3 as you press buttons. I think you need a pull up on pin 3 as well - it might be open collector.

Go electric!
Happy electric car owner / builder

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sgomes wrote:
I'm not sure about all those signals. I can't find my original notebook. However, I can tell you that I applied 3.3V to pins 2 and 4. Then I looked for signals coming out of pin 3 as you press buttons. I think you need a pull up on pin 3 as well - it might be open collector.

I'll have a go at it again tonight. Thanks for the info.

Mike

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sgomes wrote:
I'm not sure about all those signals. I can't find my original notebook. However, I can tell you that I applied 3.3V to pins 2 and 4. Then I looked for signals coming out of pin 3 as you press buttons. I think you need a pull up on pin 3 as well - it might be open collector.

Okay, Without any pullup I'm getting a signal. With a 10K pullup it was like it was never able to pull it low.

The smallest pulse width I measured was about 104us leaving me to believe it's running at 9600 baud but the longest frame is about 930us leading me to believe it's only using 9 bits 1 start, 7 data and 1 stop ?

Is your file with the codes still available?

Thanks,
Mike

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That certainly sounds pretty odd. I believe I had the same baud rate but mine was 8n1. I'd plot out a few of them and see if you can make them match up with the key codes bellow. try inverting things to see if you can make it 8n1. Like I said before, mine was inverted however. Here is the keymap. The capital letters are just place holders for the various function buttons:

const char keymap[58][2]={
0,'A',
1,'U',
2,'C',
3,'F',
4,'S',
5,'D',
6,'T',
7,'O',
8,'1',
9,'2',
10,'3',
11,'4',
12,'5',
13,'6',
14,'7',
15,'8',
16,'q',
17,'w',
18,'e',
19,'r',
20,'t',
21,'y',
22,'u',
23,'i',
24,'a',
25,'s',
26,'d',
27,'f',
28,'g',
29,'h',
30,'j',
31,'k',
32,'z',
33,'x',
34,'c',
35,'v',
36,'b',
37,'n',
38,'m',
39,'.',
41,'M',
42,'9',
43,'0',
44,'o',
45,'p',
46,'l',
47,'=',
48,'^',
49,'|',
50,'<',
51,'>',
56,'P',
57,'H',
58,'T',
59,'F',
60,' ',
61,'E',
126,'W'
};

Go electric!
Happy electric car owner / builder

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oh and I remember that some of these keyboards had separate codes for when you pushed the button down and a different code when you released it. I'm not sure if this was one of those keyboards. As I remember the MSb was set or something for all the codes it sent when you released the buttons. Have fun!

Go electric!
Happy electric car owner / builder

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sgomes wrote:
oh and I remember that some of these keyboards had separate codes for when you pushed the button down and a different code when you released it. I'm not sure if this was one of those keyboards. As I remember the MSb was set or something for all the codes it sent when you released the buttons. Have fun!

Thanks for the info! I'll check it later today. Here is the schematic I traced out so far.

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Well, that looks like an inverter to me! Also explains why your 10k pullup made it stop working.

Go electric!
Happy electric car owner / builder

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sgomes wrote:
Well, that looks like an inverter to me! Also explains why your 10k pullup made it stop working.

Yeah, It was already obvious that it was inverted. I had a brain fart when I measured the frame width because I was measuring as though the stop bit was high :oops:

So it probably is 8 data bits. I'll verify the codes when I'm back at home later.

Thanks,
Mike

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Works perfect! And it is 8N1 9600. I just tapped right in to the PC pin 23 to get a non inverted signal which also happens to be a lot cleaner signal. It looks like I'm getting the same codes as you and the key release does send the code back twice with the msb set. I'm not sure why it sends it twice but easy enough to accommodate.

Thanks again for your help. As I mentioned before I have extra units so if you want one just PM me a shipping address.

Mike

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You're very kind. I have a few myself already. I was worried they weren't going to last so I bought a few. Thanks though. Good luck! I think adding a full keyboard to your apps. makes a huge difference.

Go electric!
Happy electric car owner / builder