| ??? 04/15/05 12:09 Read: times |
#91625 - SETB SDA Responding to: ???'s previous message |
If your are using the 8051 port pins in a quasi-bidirectional mode for an I2C interface you MUST set the SDA pin to a "1" in its output latch before you can read in the state of the SDA line from the external peripheral device. MUST MUST...
You also need pullup resistors. I always specify 4.7K resistors on I2C busses. Without a value in this range the signal transition times on SDA and SCL to a high level get too long to achieve any kind of reasonable bit rate. I've seen hardware designers try to get by with 47K or 22K pullups.....do not believe that it works. Michael Karas Michael Karas |
| Topic | Author | Date |
| Bit Bang i2c | 01/01/70 00:00 | |
| You should | 01/01/70 00:00 | |
| Errr | 01/01/70 00:00 | |
| a slight problem | 01/01/70 00:00 | |
| I was | 01/01/70 00:00 | |
| Licence | 01/01/70 00:00 | |
| call it SMB | 01/01/70 00:00 | |
| maybe different | 01/01/70 00:00 | |
| Maybe! | 01/01/70 00:00 | |
| Correction! | 01/01/70 00:00 | |
| SETB SDA | 01/01/70 00:00 | |
| misunderstanding? | 01/01/70 00:00 | |
| re: | 01/01/70 00:00 | |
| Thanks to Atmel | 01/01/70 00:00 | |
| 'Stub' resistors missing? | 01/01/70 00:00 | |
| Pull ups ? | 01/01/70 00:00 | |
| Not those... | 01/01/70 00:00 | |
| Rp | 01/01/70 00:00 | |
| IIC is owned by philips why not go there | 01/01/70 00:00 | |
| You're right! | 01/01/70 00:00 | |
| Set port as input - NO SUCH THING! | 01/01/70 00:00 | |
| oh yes there is | 01/01/70 00:00 | |
| Yes, but not here? | 01/01/70 00:00 | |
| nowhere in the documentation | 01/01/70 00:00 | |
| one more reason not to rely on testing | 01/01/70 00:00 | |
| one more reason not to rely on testing | 01/01/70 00:00 | |
| Catch 'em young ... | 01/01/70 00:00 | |
Yes | 01/01/70 00:00 |