| ??? 05/02/07 02:34 Modified: 05/02/07 03:23 Read: times |
#138426 - I2c Pullup\'s Responding to: ???'s previous message |
The value of I2c pullup resistors have a lower limit and an upper limit.
A low limit is becasue the I2c driver has a current sink limit and your circuit may be battery powered so you want to reduce current drain. A high limit is becuse a high value R will cause slower rise times and not allow higher speed I2C transmission (also you need to check the logic current thresholds - so that the R can drive the logic inputs). So for your application a R little on the low side (not too low) would be OK. The I2c manual gives some graphs on pullup R values. For bit-bash I2C - I suggest to riggorously test i2c functions. Sometimes.... I2c transmission gets stuck waiting in a loop for an ACK... so you may need to handle a time out situation where ... after X mS of time. Re-Initialise the I2c bus or take other action. Transients on the supply or elsewhere can cause false clocking on the I2c buss. So you need to handle this also. Some I2c devices have glitch filters and ignore some transients. Just my 2 cents worth. Joe |
| Topic | Author | Date |
| i2c - hardware | 01/01/70 00:00 | |
| More information needed Eg Distance | 01/01/70 00:00 | |
| Re: more information | 01/01/70 00:00 | |
| I'd add none | 01/01/70 00:00 | |
| Dosn't work on 29 February, then? | 01/01/70 00:00 | |
| one day off | 01/01/70 00:00 | |
| I2c Pullup\'s | 01/01/70 00:00 | |
| Thanx | 01/01/70 00:00 | |
| All this can be ignored, if you use chips with har | 01/01/70 00:00 | |
| Yes, I2c hardware on board is desired | 01/01/70 00:00 | |
| language? | 01/01/70 00:00 | |
on-board ..I mean on-chip | 01/01/70 00:00 |