begin spi

rpi_spi/2023-12-29_pi-spi-rates.md

+## 2023 12 29
+
+OK, SPI is looking pretty good; actual bit times are identical to what-they-should-be, so I'm not even going to note them down (whereas UART out of the PI has some drift, probably strange BAUD fractional maths). 
+
+So, there's just the question of waveform integrity, and (probably) the ability of the RP2040 to keep up, and there's the actually-delineating-and-echoing-etc test. 
+
+I'd like to look at some scope traces first, but I should probably do it in context (i.e. actually driving a pin, not free air), so I'll setup my little test rig...
+
+- female-to-male,
+- usb-to-image-capture-on-the-scope ? 
\ No newline at end of file

rpi_spi/code/pi_spi.py

+import spidev 
+
+spi = spidev.SpiDev()
+spi.open(0, 0)
+spi.max_speed_hz = 12000000
+
+for i in range(100000):
+    spi.xfer([12, 14, 95])
+
+spi.close() 
\ No newline at end of file