Matt Try as I may I cannot solve my problems attempting to use the 74HTC08 but I will keep trying.
Can I ask you a question regarding the resistor dividor networks shown in the tutorial schematic illustrating the use of the 23k256 sram. Two of the SPI lines ( SS and SDO) use 1.5k/3.3k resistors to step down the voltage but for the CLK line you indicate 470/2k. Why does this divider network differ from the other two lines. Understanding this may just help me to see what I have done wrong using the 74HTC08. As you have probably guessed my knowledge is weak on the electronics side of things. Kind Regards Dave Paxton On Friday, 7 September 2012 10:09:07 UTC+1, mattschinkel wrote: > > Sorry, I've been to busy to test anything. > > If your getting 0xFF there must be something wrong with the hardware or > your connections. You do not need to do any level conversion for the SDO > line (signal out of 235254 to the PIC). > > 74HCT08 will work, I've done it in the past. > > Matt. > > On Tuesday, September 4, 2012 8:16:03 AM UTC-4, PDSACAA wrote: >> >> Matt >> I knocked out a board using the 74HCT08 logic IC and a LD1117V33 voltage >> regulator to guarantee a 3.3V supply voltage to >> the IC. >> I jumpered together the pair of logic input pins on each of the 4 IC >> gates and fed the PIC outputs CLK,SDO and SS >> to 3 of these IC input pairs. Fed the 3 IC outputs to the 28K256. The >> 28k256 SO line went straight to PIC SDI pin as before and as >> per tutorial schematic. >> I checked all of the IC output voltage levels using simple program to >> raise or lower PIC pins. These seemed ok dropping to 0v >> low or rising to 3.68V high. >> >> Unfortunately when running sample program to read/write 28k256 via the >> 74HCT08, I get nothing but FF's. >> I have checked, checked and rechecked wiring but can't find anything >> wrong. >> >> I take it that it goes without saying that the 74HCT08 can switch at the >> clock speeds the SPI routines throw at it? >> I dropped the CLK speed down to the minimum but this showed no difference. >> Have you got any ideas where I might have slipped up? >> >> At least the resistor divider network worked up to a point!! >> >> Regards >> Dave >> >> On Sunday, 2 September 2012 02:51:10 UTC+1, mattschinkel wrote: >>> >>> Please try the 74HCT08. The resistor divider should work as well, but >>> 74HCT08 will give you better signals. >>> >>> -- You received this message because you are subscribed to the Google Groups "jallib" group. To view this discussion on the web visit https://groups.google.com/d/msg/jallib/-/rII8uV_kck4J. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/jallib?hl=en.
