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Same ground
valusoft wrote: All of the "grounds" must be in common or there is no reference for the voltages present.   Ok. So that would be common to the VCC, the USB +5V in this case...
Saturday, 30 May 2020 - 03:43
Basic question on buffered transfer of data on an 8-bit bus
barnacle wrote: The traditional use of  a 245is to enable bidirectional communication between two busses. Which is what you want... you'd often find it, for example, between...
Tuesday, 7 April 2020 - 02:06
Basic question on buffered transfer of data on an 8-bit bus
I think you're suggestion is good, without clocking, as I had also thought.  The 74HC245 has a directional pin, which can act and input/output direction.  I think...
Sunday, 5 April 2020 - 20:18
Do I really need to use the /SS pin for SPI between two ATMEGAs?
strontiumdog wrote: The answer is MAYBE.   Master - Does not NEED to use /SS, its just an IO you can use any pin, or none, and the Master will send what you want. However you...
Tuesday, 16 July 2019 - 23:57
Generating a 4Mhz square wave/clock for the ATMEGA644P
digitalDan wrote: Vpp = 52.8 V  !!?!?!? Is this just a case of using a 1:1 probe and the scope thinks it's 10:1 (or a 10:1 and the scope thinks it's 100:1)? If it really is...
Wednesday, 10 July 2019 - 23:37
Generating a 4Mhz square wave/clock for the ATMEGA644P
avr-mike wrote: unebonnevie wrote: At 4.03Mhz!  0.3Mhz extra.  Probably I can set OCR0B to 1 to get rid of the extra 0.03Mhz.   Your clock is probably running at 8...
Wednesday, 10 July 2019 - 21:22
Generating a 4Mhz square wave/clock for the ATMEGA644P
avr-mike wrote: It sounds like you have an 8MHz clock and want to generate a 4MHz output.  For this, you do not need PWM. Set up a timer to run at full speed in Clear Timer...
Wednesday, 10 July 2019 - 20:37
Generating a 4Mhz square wave/clock for the ATMEGA644P
avrcandies wrote: The nice thing about a divider is it will give you "exactly" 50% duty, regardless of the input duty cycle  (neglecting any slight variations, and time...
Wednesday, 10 July 2019 - 19:16
Generating a 4Mhz square wave/clock for the ATMEGA644P
joeymorin wrote: Or, if the app can live with it, divide the system clock by two via CLKPR   Not familiar with the CLKPR option.  Found the post  https://www....
Tuesday, 9 July 2019 - 14:11
Generating a 4Mhz square wave/clock for the ATMEGA644P
ka7ehk wrote: If it needs to be a true PWM (that is, varying duty cycle), then no, you cannot from a Mega644. You need something that has a clock, significantly higher than 4MHZ,...
Tuesday, 9 July 2019 - 02:20
I/O operating voltages between two ATMEGAs
Thanks, all.  A 74LVC245 should help.  " Inputs can be driven from either 3.3 V or 5 V devices. When disabled, up to 5.5 V can be applied to the outputs. These features...
Friday, 14 June 2019 - 06:09
I/O operating voltages between two ATMEGAs
tpappano wrote:The 3.3V should be OK with 5V input, that is, no need to level shifting or anything? Why should it be ok? (It is not) A read of the data sheet would be a good...
Wednesday, 12 June 2019 - 23:36

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