From 68c80359ba0983bc21a18c0270025be9b441c0bb Mon Sep 17 00:00:00 2001
From: Wojciech Kosior <kwojtus@protonmail.com>
Date: Tue, 29 Dec 2020 19:56:04 +0100
Subject: add the ability to include additional data at the end of bitstream
 image and prepare an example, that reads thic data through SPI and displays
 it

---
 examples/example3a_spi_wasm/instructions.wat | 115 +++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 examples/example3a_spi_wasm/instructions.wat

(limited to 'examples/example3a_spi_wasm/instructions.wat')

diff --git a/examples/example3a_spi_wasm/instructions.wat b/examples/example3a_spi_wasm/instructions.wat
new file mode 100644
index 0000000..f09e080
--- /dev/null
+++ b/examples/example3a_spi_wasm/instructions.wat
@@ -0,0 +1,115 @@
+;; See instructions.wat of soc_print_number test. A lot has been taken from
+;; there.
+;; Relevant addresses are VGA text memory (0xFFC00), VGA regs (0x100600),
+;; lower half of timer reg (0x1BFC08), SPI memory (0x13FC00),
+;; SPI bytes_to_output reg (0x13FE00), SPI bytes_to_receive reg (0x13FE02)
+;; and SPI operating reg (0x13FE04).
+
+(module
+ (memory 0 2)
+ (func $main
+       (local $transfers i32)
+       (local $offset i32)
+       (local $address i32)
+       (local $index i32)
+
+       ;; power up flash chip
+       ;; set bytes_to_output to 1
+       (i32.store16 offset=0 align=2
+		    (i32.const 0x13FE00) (i32.const 1))
+       ;; set bytes_to_receive to 0
+       (i32.store16 offset=0 align=2
+		    (i32.const 0x13FE02) (i32.const 0))
+       ;; release power-down SPI command
+       (i32.store8 offset=0 align=1
+		   (i32.const 0x13FC00) (i32.const 0xAB))
+       ;; start SPI operation
+       (i32.store16 offset=0 align=2
+		    (i32.const 0x13FE04) (i32.const 0x1))
+
+       ;; wait for at least 3000 ns after command gets sent
+       ;; reset the timer
+       (i32.store16 offset=0x0 align=2
+		    (i32.const 0x1BFC08) (i32.const 0x0))
+
+       ;; loop until 45 ticks pass; 45 ticks is 3600 ns; additional 600ns
+       ;; is enough for power-up command to be sent
+       (loop $again
+	     (br_if $again (i32.lt_u
+			    (i32.load16_u offset=0x0 align=2
+					  (i32.const 0x1BFC08))
+			    (i32.const 45))))
+
+       ;; we'll transfer 2400 bytes by making 5 transfers of 480 bytes;
+       ;; our SPI peripheral can transfer at most 511 bytes in one SPI command
+       (set_local $transfers (i32.const 0))
+
+       (loop $outer
+	     ;; set bytes_to_output to 5
+	     (i32.store16 offset=0 align=2
+			  (i32.const 0x13FE00) (i32.const 5))
+	     ;; set bytes_to_receive to 480
+	     (i32.store16 offset=0 align=2
+			  (i32.const 0x13FE02) (i32.const 480))
+	     ;; fast read SPI command
+	     (i32.store8 offset=0 align=1
+			 (i32.const 0x13FC00) (i32.const 0x0B))
+	     ;; prepare address - first, compute current offset
+	     (set_local $offset (i32.mul (get_local $transfers)
+					 (i32.const 480)))
+	     ;; then, add computed offset to base address of 135100
+	     (set_local $address (i32.add (get_local $offset)
+					  (i32.const 135100)))
+	     ;; store the address in big endian
+	     (i32.store16 offset=0 align=2
+			  (i32.const 0x13FC02)
+			  (i32.div_u (get_local $address)
+				     (i32.const 256)))
+	     (i32.store8 offset=0 align=1
+			 (i32.const 0x13FC03) (get_local $address))
+	     (i32.store8 offset=0 align=1
+			 (i32.const 0x13FC01)
+			 (i32.div_u (get_local $address)
+				    (i32.const 65536)))
+	     ;; start SPI operation
+	     (i32.store16 offset=0 align=2
+			  (i32.const 0x13FE04) (i32.const 0x1))
+	     ;; force wait for operation completion
+	     (i32.store16 offset=0 align=2
+			  (i32.const 0x13FE00) (i32.const 0))
+
+	     ;; assume transferred data to be ascii text and print it to screen
+	     ;; initialize index to 0
+	     (set_local $index (i32.const 0))
+	     ;; copy characters in a loop
+	     (loop $inner
+		   ;; copy 4 characters to VGA memory
+		   (i32.store offset=0xFFC00 align=4
+			      (i32.add (get_local $index)
+				       (get_local $offset))
+			      (i32.load offset=0x13FC00 align=4
+					(get_local $index)))
+		   ;; increase index
+		   (set_local $index (i32.add (get_local $index)
+					      (i32.const 4)))
+		   ;; loop condition
+		   (br_if $inner (i32.lt_u
+				  (get_local $index)
+				  (i32.const 480))))
+
+	     ;; increase transfers count
+	     (set_local $transfers (i32.add (get_local $transfers)
+					    (i32.const 1)))
+
+	     ;; switch LED2
+	     (i32.store16 offset=0x0 align=2
+			  (i32.const 0x1BFC06)
+			  (i32.rem_u (get_local $transfers) (i32.const 2)))
+
+	     ;; if less than 5 transfers were done, continue with another one
+	     (br_if $outer (i32.lt_u (get_local $transfers) (i32.const 5))))
+
+       ;; write a non-zero value to the VGA power-on reg at 0x100600 (0x100A00)
+       (i32.store16 offset=0x0 align=2
+		    (i32.const 0x100600) (i32.const 0x1)))
+ (export "main" (func $main)))
-- 
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