| ??? 01/10/10 15:09 Read: times |
#172317 - ADC0809 problem |
Hi,
I am interfacing an ADC0809 with Microchip PIC18F4550 (Wait.. it is also related to 8051). To channel 1 of ADC0809, a potentiometer voltage divider is connected. What happens is this input voltage is at 4.5V initially till ALE pulse goes high. The moment ALE goes high (As per ADC datasheet, ALE rising edge latches address data into the ADC) this voltage drops down to 2V. ADC then measures this 2V and outputs equivalent digital data. Strange thing is this does not happen with 8051(P89V51RD2). The input voltage is not at all affected. This is what it should be. I have compared program flow (both progams are in C), pulse widths, timings, voltage levels on pins etc. of 8051 and PIC and found no significant difference. Anyone can guide what can be the cause or how to troubleshoot it? Thanks p.s. I am posting this thread on microchip forum too. |
| Topic | Author | Date |
| ADC0809 problem | 01/01/70 00:00 | |
| Is the very same ADC chip in both cases? | 01/01/70 00:00 | |
| From time to time... | 01/01/70 00:00 | |
| Datasheet read, same hardware | 01/01/70 00:00 | |
| Define 1000000000% | 01/01/70 00:00 | |
| Thoughts... | 01/01/70 00:00 | |
| Solved partially | 01/01/70 00:00 | |
| So the cap did help? | 01/01/70 00:00 | |
| RE: That cap did help? | 01/01/70 00:00 | |
| The input multiplexer is damaged! | 01/01/70 00:00 | |
| Discharge diode | 01/01/70 00:00 | |
| RE: The input multiplexer is damaged | 01/01/70 00:00 | |
| Indeed, a very poor design!!! | 01/01/70 00:00 | |
RE: Indeed, a very poor design!!! | 01/01/70 00:00 |