| ??? 01/16/07 14:14 Read: times |
#130880 - 5V->3V conversion and vice versa Responding to: ???'s previous message |
This has been discussed many times before.
If it's only unidirectional (and every indication is that it is), a resistor divider on the line from '51 to the module will be just fine (especially at blazing 9600 bauds). A diode (Schottky) maybe, just to be sure, at the module-side of signal to the +3V line. Also maybe a series resistor plus an another diode to +3V on the line back from module to '51 - note that the weakest of "pullups" to +5V is always on on the '51 port, sourcing maybe a few uAs, but just at around 2V (which is dangerously close to 3V) the strong pullup might start to open... If you want to be more sophisticated, have a look at Philips'/NXP's appnote on I2C level conversion (I'll try to dig out the link), but that's maybe a bit overcomplicated as it needs to be bidirectional. The 74xxxxx245 is certainly an overkill in every respect, but the safest possible way... --- The MAX232-issue is, that IF you have it on board, you might need to kick it out... It appears that the module does not need RS232 levels (the +-12V thingy), but they tried to make it as unclear as possible on that webpage and in the linked documents (for me it appears that they have at least 3 different versions of the product and intermix the documentation freely). I'd also expect maybe some help from the module vendor (I doubt you are the only one trying to tie their module into a 5V system)... --- I thought a picture of the board not documentation; but that was just to help you to identify the parts, never mind. Jan Waclawek |
| Topic | Author | Date |
| AT89C55WD UART voltages. | 01/01/70 00:00 | |
| Level translation | 01/01/70 00:00 | |
| Thanks for that. | 01/01/70 00:00 | |
| Real? | 01/01/70 00:00 | |
| Real | 01/01/70 00:00 | |
| Reak! | 01/01/70 00:00 | |
| Voltage. | 01/01/70 00:00 | |
| Pins | 01/01/70 00:00 | |
| Pins | 01/01/70 00:00 | |
| the peculiar port structure of '51 | 01/01/70 00:00 | |
| The Socket | 01/01/70 00:00 | |
| Socket | 01/01/70 00:00 | |
| HW issues | 01/01/70 00:00 | |
| I am on the road, but someone can verify | 01/01/70 00:00 | |
| SN74LVC4245A | 01/01/70 00:00 | |
| 5V->3V conversion and vice versa | 01/01/70 00:00 | |
| If this is CMOS | 01/01/70 00:00 | |
| No insistance. | 01/01/70 00:00 | |
a link would be nice | 01/01/70 00:00 | |
| PLCC44 | 01/01/70 00:00 | |
| why AT89C55WD? | 01/01/70 00:00 | |
| Read the thread! | 01/01/70 00:00 | |
| AT89LV55? | 01/01/70 00:00 | |
| What is the blue tooth module? | 01/01/70 00:00 | |
| Module | 01/01/70 00:00 | |
| modules | 01/01/70 00:00 | |
| Modules | 01/01/70 00:00 |