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SAM4S SPI - when receiving several bytes with the PDC, the transfer stalls after one byte of clocks
OK - here is what I am doing to kick off a SPI read now, using the PDC.   With the busy-waiting code, I left it running a torture test of writing data and reading back data...
Friday, 7 June 2019 - 15:23
SAM4S SPI - when receiving several bytes with the PDC, the transfer stalls after one byte of clocks
Thanks for the suggestion, Josh. I will give that a try.   It makes a certain amount of sense that the PDC would need to write in order to read, because of course that's how...
Friday, 7 June 2019 - 13:55
SAM4S SPI - when receiving several bytes with the PDC, the transfer stalls after one byte of clocks
Some followup:   Out of desperation I changed the receive routine to do busy-waiting like so:   /* If RDRF is set, read RDR to clear it, so we get fresh data */ if...
Wednesday, 5 June 2019 - 22:27
ATmega16u2 Minimal Connections to test ISP?
It's late 2017 and the datasheet for the ATmega8U2 still has the incorrect text about the default clock configuration in section 8.3.1.   Yes, it is correct elsewhere in the...
Friday, 10 November 2017 - 19:27
Atmel ICE Can't Talk to a ATmeg8U2 on a Breadboard, New (_and_ old) Setup
Ah, OK, so you were correct about the USB chip needing the external crystal, although I originally read your comment as being unsure about (both) the clock configuration and the...
Wednesday, 8 November 2017 - 22:04
Atmel ICE Can't Talk to a ATmeg8U2 on a Breadboard, New (_and_ old) Setup
No, I did not miss it. Dave said "the 8u2 might be different" and that he "[had] not checked the datasheet." So I did. It _appeared_ that the 8U2 was different, but Dave's...
Wednesday, 8 November 2017 - 21:04
Atmel ICE Can't Talk to a ATmeg8U2 on a Breadboard, New (_and_ old) Setup
Fine, "that _part_ of the datasheet is wrong."   Does it contradict itself? Very well, it contradicts itself. I guess, like Whitman, it is large, it contains multitudes 
Wednesday, 8 November 2017 - 20:19
Atmel ICE Can't Talk to a ATmeg8U2 on a Breadboard, New (_and_ old) Setup
OK -- on the off chance that the datasheet is wrong, and these chips arrived programmed to run from an _external_ clock, I ordered some 8MHz crystals. They arrived today, I added...
Wednesday, 8 November 2017 - 19:18
Atmel ICE Can't Talk to a ATmeg8U2 on a Breadboard, New (_and_ old) Setup
Here's a picture of the scope: yellow is RESET, blue is MOSI, purple is MISO.   Hmmm, well, that came out rotated, but the basic idea is that MISO is not doing anything...
Friday, 3 November 2017 - 22:27
Atmel ICE Can't Talk to a ATmeg8U2 on a Breadboard, New (_and_ old) Setup
From what I can tell, the DFU bootloader is not on the 8U2 (but is on the 16). Even if it is, I think reading the chip ID ought to be possible using ISP.   I had a cap on GND...
Friday, 3 November 2017 - 21:25
Atmel ICE Can't Talk to a ATmeg8U2 on a Breadboard, New (_and_ old) Setup
Oh, FFS. You know, I even went through this before with a previous design where we actually use the internal ADC, on a 461A. I forgot that AVCC has to be up even if you aren't...
Friday, 3 November 2017 - 21:15
Atmel ICE Can't Talk to a ATmeg8U2 on a Breadboard, New (_and_ old) Setup
Took a fresh chip out of the original package from Digi-key and my EE co-worker built up a new board. Tested continuity on every pin with a voltmeter. Solder connections look...
Friday, 3 November 2017 - 19:59

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