| ??? 02/15/05 19:25 Read: times |
#87568 - A possible solution Responding to: ???'s previous message |
Sebastián Viviani said:
Hi, I am working with a 7 segment LCD, and trying to drive it with an 89s52. I had almost everything done, but I am having some dummy problem with the output levels...
As I have 2 different backplanes, I found a lot of AN's for other uC (PIC, Zilog, etc) that showed that by building a 3 level signal (0, 2.5 and 5 volts), with a different phase, it's possible to do all the stuff playing with signal phases, and TTL outputs. Try connecting one of the open drain outputs via a pullup (say 4K7) to Vcc and then connect another 4K7 resistor between this open drain output and another open drain output. The ouput at the junction of the two resistors is 5V when both port pins are hi, 0V when the one connected to the pullup is taken low and 2.5V when the other port pin is taken low (and the first set hi). Hope this makes sense. Ian |
| Topic | Author | Date |
| three level output with resistors | 01/01/70 00:00 | |
| Buffer your pins... | 01/01/70 00:00 | |
| the advantage of '51 | 01/01/70 00:00 | |
| Try ATmega8515 | 01/01/70 00:00 | |
| or try a modern '51 | 01/01/70 00:00 | |
| ... and are not pin compatible... | 01/01/70 00:00 | |
| pin-compatible but reset is negative | 01/01/70 00:00 | |
| What is less pain? | 01/01/70 00:00 | |
| not any more | 01/01/70 00:00 | |
| where do you get your info? | 01/01/70 00:00 | |
| the horses mouth | 01/01/70 00:00 | |
| hmmmm | 01/01/70 00:00 | |
| pico gates, | 01/01/70 00:00 | |
| if just one unit or maybe | 01/01/70 00:00 | |
| 3 levels possible on 8051 without buffer | 01/01/70 00:00 | |
| the goalpost | 01/01/70 00:00 | |
| gotcha | 01/01/70 00:00 | |
The solution, but ... (almost off topic) | 01/01/70 00:00 | |
| A possible solution | 01/01/70 00:00 | |
| deja vu? | 01/01/70 00:00 | |
| Whoops! | 01/01/70 00:00 | |
| flat style | 01/01/70 00:00 | |
| aka | 01/01/70 00:00 | |
| R-2R | 01/01/70 00:00 | |
| R-2R? | 01/01/70 00:00 |