| ??? 05/08/07 07:15 Read: times |
#138806 - Apparently, you haven't done that either, Erik Responding to: ???'s previous message |
Erik Malund said:
Have you made this keypad encoder/LCD combination function using ASM?
what good would that do? If you do not understand how the KP interrupt worls in a LPC (it should be used ONLY for wake up, the immmediately disabled and a normal keyscan started) it makes no difference what language you code in. Erik Just exactly what has the LPC to do with this thread? The 74C922 and 74C923 are matrix-keypad encoder chips for either 4x4 or 4x5 matrices, respectively. They have row and column connections for the switch matrix and provide a 4 or 5-bit code, an data-available strobe, and an output enable input for tri-state applications. The scan rate and debounce time constant are determined by external capacitors. When the Data-Available strobe goes positive, a new keypress is detected and its code is avaiable if output enable is taken low before the strobe goes away. My concern is that the O/P didn't list his MCU nor did he indicate what sort of interrupt he's using. If he uses a positive-edge triggered interrupt, he can rely on one per keypress. If he uses a level-triggered interrupt, he has to clear it before the next keypress, else he'll miss it. If he fails to clear ckear and disable the level-sensitive interrupt, he'll likely get multiple interrupts for one keypress unless he handles it carefully. RE |
| Topic | Author | Date |
| external interrupt using by keypad encoder 74c922 | 01/01/70 00:00 | |
| that code does not compile | 01/01/70 00:00 | |
| it is wotking now... | 01/01/70 00:00 | |
| reply | 01/01/70 00:00 | |
| strongly and totally disagree | 01/01/70 00:00 | |
| Have you carefully read the datasheet? | 01/01/70 00:00 | |
| what good would that do? | 01/01/70 00:00 | |
| Apparently, you haven't done that either, Erik | 01/01/70 00:00 | |
| Misread? | 01/01/70 00:00 | |
| 922 and 922 | 01/01/70 00:00 | |
| Here we go again ... | 01/01/70 00:00 | |
| Why ASM | 01/01/70 00:00 | |
| Fundamental misconception | 01/01/70 00:00 | |
| nope, here is the correction | 01/01/70 00:00 | |
| what about, for a change, answering a question? | 01/01/70 00:00 | |
| If you can\'t do it in ASM, you can\'t do it at all. | 01/01/70 00:00 | |
| LCD Routine take time. | 01/01/70 00:00 | |
| it is a good idea, but the problem in another... | 01/01/70 00:00 | |
what an understatement | 01/01/70 00:00 |