Decided to start looking at some higher power stuff in µPython which is not available through the standard APIs -> have to start register hacking instead. The datasheet is superb and explains everything needed.
Day 0: switch on and off GPIO output by poking registers, not cheating by using the machine.Pin interface.
Code:
from machine import mem32
import time
# set up GPIO25 (the LED) by hand and switch it on and off by
# poking values into registers - see datasheet 2.19.6.1
led = 25
# have to set the pin to SIO mode in the control register
mem32[0x40014000 | 0xCC] = 0x5
# pad drive mode - 12mA
mem32[0x4001C000 | 0x68] = 0x3 << 4
# enable output
mem32[0xD0000000 | 0x20] = 0x1 << led
def on():
# set the right bit as on
mem32[0xD0000000 | 0x14] = 0x1 << led
def off():
# set the right bit as clear
mem32[0xD0000000 | 0x18] = 0x1 << led
for j in range(10):
on()
time.sleep(1)
off()
time.sleep(1)
would have been fun to not use time.sleep() instead finding another way to poke the machine into sleeping for a while.
That is a really low level thing which I don’t actually understand right now, but can play with it by changing the hello_interp C program to bit bang registers to drive the interps. Turns out it was really simple viz:
from machine import mem32
# initialise lane 0 on interp
mem32[0xD0000000 | 0xAC] = 0x1F << 10
# set up 9 x table example
mem32[0xD0000000 | 0x80] = 0
mem32[0xD0000000 | 0x88] = 9
for j in range(10):
print(mem32[0xD0000000 | 0x94])
Yes, this prints 9x table as expected.