Merge pull request #29 from ivand58/bit-band

Bit band calculation for cortex M3/4

4 files changed, 81 insertions, 1 deletions

diff --git a/build/arm-stm32f103/Makefile b/build/arm-stm32f103/Makefile
index f6b026b..3cce6cd 100644
--- a/build/arm-stm32f103/Makefile
+++ b/build/arm-stm32f103/Makefile
@@ -22,6 +22,7 @@ include $(TOPDIR)/src/app/$(MYNAME)/targets.mk
 ifeq ("$(wildcard $(STMLIB))","")
 	$(info You need the STM Standard Peripheral Library)
 	$(info Get it from http://www.st.com/content/st_com/en/products/embedded-software/mcus-embedded-software/stm32-embedded-software/stm32-standard-peripheral-libraries/stsw-stm32054.html)
+	$(info Get it from https://my.st.com/content/ccc/resource/technical/software/firmware/48/ab/e5/17/0d/79/43/74/stsw-stm32054.zip/files/stsw-stm32054.zip/_jcr_content/translations/en.stsw-stm32054.zip)
 	$(info Unpack it into the parent directory of the cforth/ tree)
 	$(error )
 endif
diff --git a/src/app/arm-stm32f103/app.fth b/src/app/arm-stm32f103/app.fth
index 0052090..1dbf783 100644
--- a/src/app/arm-stm32f103/app.fth
+++ b/src/app/arm-stm32f103/app.fth
@@ -1,5 +1,5 @@
 \ Load file for application-specific Forth extensions
-
+fl ../../cpu/arm/cortex-m3/bitband.fth
 fl ../../lib/misc.fth
 fl ../../lib/dl.fth
 $3000 $5000 npatch load-base
diff --git a/src/app/arm-stm32f103/example.fth b/src/app/arm-stm32f103/example.fth
new file mode 100644
index 0000000..46a9dc7
--- /dev/null
+++ b/src/app/arm-stm32f103/example.fth
@@ -0,0 +1,58 @@
+\ Example event loop for periodic ADC sampling
+
+\ Exponential smoothing filter
+#10000 value filter-denom
+ #9000 value filter-alpha
+0 value smoothed-adc
+: filter  ( new-value -- filtered value )
+   filter-denom filter-alpha - *    ( new-value'*denom )
+   smoothed-adc filter-alpha *  +   ( smoothed-value*denom )
+   filter-denom /                   ( smoothed-value' )  \ Rounded division
+   dup to smoothed-adc              ( filtered-value )
+;
+
+#300 value adc-ms     \ The sampling period in milliseconds
+
+0 value next-adc-time
+
+: set-next-adc-time  ( -- )  get-msecs adc-ms + to next-adc-time  ;
+: adc-time?  ( -- flag )  get-msecs next-adc-time - 0>=  ;
+: check-adc  ( -- )
+   adc-time?  if
+      set-next-adc-time
+      adc@ dup ." Current: " .d     ( val )
+      ." filtered " filter  .d  cr  ( )
+   then
+;
+
+#800 value led-ms     \ The sampling period in milliseconds
+
+0 value next-led-time
+0 value led-state
+
+: set-next-led-time  ( -- )  get-msecs led-ms + to next-led-time  ;
+: led-time?  ( -- flag )  get-msecs next-led-time - 0>=  ;
+
+: check-led  ( -- )
+   led-time?  if
+      set-next-led-time
+      led-state led-gpio gpio-pin!
+      led-state 0= to led-state
+   then
+;
+
+: test  ( -- )
+   init-led
+   set-next-led-time
+
+   0 init-adc
+   set-next-adc-time     \ Set up for first periodic sample
+   adc@ drop             \ Discard the first sample which is often suspect
+   adc@ to smoothed-adc  \ Prime the smoothed value with the current value
+
+   begin
+      check-led \ Blink
+      check-adc \ Handle the ADC every so often
+      wfi       \ The processor idles here until the next timer tick
+   key? until   \ Exit when a key is pressed
+;
diff --git a/src/cpu/arm/cortex-m3/bitband.fth b/src/cpu/arm/cortex-m3/bitband.fth
new file mode 100644
index 0000000..2966409
--- /dev/null
+++ b/src/cpu/arm/cortex-m3/bitband.fth
@@ -0,0 +1,21 @@
+\ Bit-banding maps a complete word of memory onto a single bit in the bit-band
+\ region. For example, writing to one of the alias words sets or clears the
+\ corresponding bit in the bit-band region. This enables every individual bit in
+\ the bit-banding region to be directly accessible from a word-aligned address
+\ using a single LDR instruction. It also enables individual bits to be toggled
+\ without performing a read-modify-write sequence of instructions.
+
+\ Usage:
+\   variable x
+\   0 x !
+\   x 0 BITBAND 1 swap c! x @ .
+
+: bitband  ( bit adr -- aliasadr )
+   dup 5 lshift            ( bit adr byte-offset )  \ Spread low part of address; high bits will be shifted out
+   swap $f000.0000 and or  ( bit adr' )             \ Keep high nibble of address
+   $0200.0000 or           ( bit adr' )             \ Offset to bitband alias space
+   swap la+                ( aliasadr )             \ Merge bit number as 32-bit word offset
+;
+
+." Test for SFR "   5 $4001140C BITBAND $42228194 = if ." Passed" else ." Failed" then CR
+." Test for RAM " #24 $200FFFFC BITBAND $23ffffe0 = if ." Passed" else ." Failed" then CR