I set it up this way also, and the same problem but it works a bit better when I put a 1K resistor between the emitter and ground but the signal still distorted
I wish I could, but it seems like is acting up now the I was using a 74HCT04 hex inverter last night and the signal I guess was on the edge because is not working well today.
He doesn't need to mention his load. Even with a typical minimum circuit stray capacitance value, a common-emitter or common-source will not be able to drive it at 20MHz unless the collector/drain resistor is a low value.
How long is the wire (or trace) from the microcontroller to the "other chips"? How many other chips are connected, and what are they?
BTW, what was the "1.8V to 2.5V sine wave" you mentioned in post #5?
The Microcontroller is a PIC32 and the slave are STP24DP05
the I'm trying to connect 8 STP24D05 about 6 inches apart from eachother, so the last chip is 4 feet away from the microcontroller.
The Microcontroller is a PIC32 and the slave are STP24DP05
the I'm trying to connect 8 STP24D05 about 6 inches apart from eachother, so the last chip is 4 feet away from the microcontroller.
You can't do that at 20MHz, due to transmission line effects. A transistor is not going to sove your problem. Are you trying to daisy chain them, or do you have a separate line from the µcontroller output to each STP24D05?
I couldn't find STP24D05 with Google. Can you provide a link to the datasheet?
You can't do that at 20MHz, due to transmission line effects. A transistor is not going to sove your problem. Are you trying to daisy chain them, or do you have a separate line from the µcontroller output to each STP24D05?
I couldn't find STP24D05 with Google. Can you provide a link to the datasheet?
I use 5V to drive the STP24DP05 , yes sorry I miss that part yes I'm daisy chain them there a single SPI bus line that runs 4 feet and each STP24DP05 feeds from that line.
What I will try to do is slow down the clock and see if it works that way, I will do it tomorrow I been playing with this since I got up this morning.
I use 5V to drive the STP24DP05 , yes sorry I miss that part yes I'm daisy chain them there a single SPI bus line that runs 4 feet and each STP24DP05 feeds from that line.
What I will try to do is slow down the clock and see if it works that way, I will do it tomorrow I been playing with this since I got up this morning.
You may have problems with any clock frequency. The long transmission line will have reflections. The problem is with the clock rise and fall times, not the frequency per se.
Can you post a drawing of your bus topology, or at least tell us the lengths of the stubs from the bus to each STP24DP05.
Do you have a ground plane on the side of the board opposite the bus?
I use 5V to drive the STP24DP05 , yes sorry I miss that part yes I'm daisy chain them there a single SPI bus line that runs 4 feet and each STP24DP05 feeds from that line.
What I will try to do is slow down the clock and see if it works that way, I will do it tomorrow I been playing with this since I got up this morning.
yeah I been hitting my head on the wall with this , sorry I should had mention it was 4 feet long, so what I did is change the clock speed from 20Mhz to 5Mhz and it works, the bad part is that I'm using a pic32 is a very powerful chip and is like driving a ferrari in traffic, I have to start doing more search on spi bus design.