HP Forum Archive 18

[ Return to Index | Top of Index ]

HP-20B key matrix Message #1 Posted by Scott Newell on 20 July 2008, 10:01 p.m. Appears to be a 6 row (rows are inputs) by 7 column (outputs) matrix, so it could have had up to 42 keys. The on key appears to be outside the matrix. (Pressing the on key takes TP11 to ground.) Inputs: Row 0 input is pin PC19 Row 1 input is pin PC20 Row 2 input is pin PC21 Row 3 input is pin PC22 Row 4 input is pin PC23 Row 5 input is pin PC2 Outputs: Column 0 output is pin PC24 Column 1 output is pin PC25 Column 2 output is pin PC26 Column 3 output is pin PC27 Column 4 output is pin PC28 Column 5 output is pin PC29 Column 6 output is pin PC30 The matrix layout is pretty much what you'd expect, but with the rows running vertically and the columns running across the keypad. I've worked through it and can provide details if needed. Couple of weird things. 1: PC30 is not listed as a valid I/O pin in my Atmel databook. Maybe it's not bonded out on the BGA or LQFP, but is present on the CoB variant used in the HP-20B? 2: I'm a bit surprised that the on key isn't using one of the wakeup inputs. (I'm sure that design choice will make more sense once I dig into the power management.) Oh, it appears that bank A and B GPIO (50 pins total) are dedicated to the LCD column and segment drive. Guess I need to find the analog inputs.

Re: HP-20B key matrix Message #2 Posted by cyrille de Brébisson on 21 July 2008, 9:12 a.m., in response to message #1 by Scott Newell hello, since all ports are both input/outputs, rows and columns can be exchanged, so there is no 'row' 'column' like they were on the saturn. you got pretty much all the port wrong.. sorry. the ON key is on a wakup pin: the FWUP (of Fast Wakeup pin)... regards, cyrille

Re: HP-20B key matrix Message #3 Posted by Scott Newell on 21 July 2008, 10:04 a.m., in response to message #2 by cyrille de Brébisson Quote: you got pretty much all the port wrong.. sorry. Really? Weird, I even double checked my work on that one. I wonder...oh crap. I'll bet I forgot to switch to little endian mode. (OCD Commander likes to boot in big endian, even for ARM targets.) Grrr. Sorry for the noise guys, I'll rework it tonight.

[ Return to Index | Top of Index ]

Go back to the main exhibit hall