Switch PicoSoC firmware to C

picosoc/Makefile

@@ -49,8 +49,8 @@ hx8kdemo.bin: hx8kdemo.asc
 
 # ---- Example Firmware ----
 
-firmware.elf: sections.lds firmware.S
+firmware.elf: sections.lds start.s firmware.c
-	riscv32-unknown-elf-gcc -Wl,-Bstatic,-T,sections.lds,--strip-debug -ffreestanding -nostdlib -o firmware.elf firmware.S
+	riscv32-unknown-elf-gcc -Wl,-Bstatic,-T,sections.lds,--strip-debug -ffreestanding -nostdlib -o firmware.elf start.s firmware.c
 
 firmware.hex: firmware.elf
 	riscv32-unknown-elf-objcopy -O verilog firmware.elf /dev/stdout | sed -e '2,65537 d;' > firmware.hex

picosoc/firmware.S

@@ -1,126 +0,0 @@
-// write RAM code (a sequence of nops followed by ret)
-li      x5,0x00000013   // nop
-sw      x5,4(x0)
-sw      x5,8(x0)
-sw      x5,12(x0)
-sw      x5,16(x0)
-sw      x5,20(x0)
-sw      x5,24(x0)
-sw      x5,28(x0)
-sw      x5,32(x0)
-sw      x5,36(x0)
-sw      x5,40(x0)
-sw      x5,44(x0)
-sw      x5,48(x0)
-sw      x5,52(x0)
-sw      x5,56(x0)
-sw      x5,60(x0)
-sw      x5,64(x0)
-sw      x5,68(x0)
-sw      x5,72(x0)
-sw      x5,76(x0)
-sw      x5,80(x0)
-sw      x5,84(x0)
-sw      x5,88(x0)
-sw      x5,92(x0)
-sw      x5,96(x0)
-sw      x5,100(x0)
-sw      x5,104(x0)
-sw      x5,108(x0)
-sw      x5,112(x0)
-sw      x5,116(x0)
-sw      x5,120(x0)
-sw      x5,124(x0)
-sw      x5,128(x0)
-sw      x5,132(x0)
-sw      x5,136(x0)
-sw      x5,140(x0)
-sw      x5,144(x0)
-sw      x5,148(x0)
-sw      x5,152(x0)
-sw      x5,156(x0)
-sw      x5,160(x0)
-sw      x5,164(x0)
-sw      x5,168(x0)
-sw      x5,172(x0)
-sw      x5,176(x0)
-sw      x5,180(x0)
-sw      x5,184(x0)
-sw      x5,188(x0)
-sw      x5,192(x0)
-li      x5,0x00008067   // ret
-sw      x5,196(x0)
-
-// write a few chars to UART
-li      x5,0x02000004
-li      x6,104
-sw      x6,0(x5)
-li      x5,0x02000008
-li      x6,'H'
-sw      x6,0(x5)
-li      x6,'e'
-sw      x6,0(x5)
-li      x6,'l'
-sw      x6,0(x5)
-li      x6,'l'
-sw      x6,0(x5)
-li      x6,'o'
-sw      x6,0(x5)
-li      x6,' '
-sw      x6,0(x5)
-li      x6,'W'
-sw      x6,0(x5)
-li      x6,'o'
-sw      x6,0(x5)
-li      x6,'r'
-sw      x6,0(x5)
-li      x6,'l'
-sw      x6,0(x5)
-li      x6,'d'
-sw      x6,0(x5)
-li      x6,'!'
-sw      x6,0(x5)
-li      x6,'\r'
-sw      x6,0(x5)
-li      x6,'\n'
-sw      x6,0(x5)
-
-#if 0
-// switch spimemio to continous qspi ddr mode
-li      x5,0x02000000
-li      x6,0x80000071
-sw      x6,0(x5)
-#endif
-
-// setup gpio address in x5
-li      x5,0x03000000
-sw      x0,0(x5)
-
-// initial entry point into RAM code
-li      x3,4
-
-// initialize RAM counter
-sw      x0,0(x0)
-
-// start of loop. remember this address
-auipc   x4,0
-
-// execute RAM code, come back here
-jalr    x3
-
-// load counter and increment
-lw      x6,0(x0)
-addi    x6,x6,1
-
-// store counter and update gpios
-sw      x6,0(x5)
-sw      x6,0(x0)
-
-// calculate new entry point into RAM code
-slli    x3,x6,2
-andi    x3,x3,127
-addi    x3,x3,32
-
-// execute RAM code, come back to start of loop
-mv      x1,x4
-jr      x3

picosoc/firmware.c

@@ -0,0 +1,27 @@
+#include <stdint.h>
+
+#define reg_spictrl (*(volatile uint32_t*)0x02000000)
+#define reg_uart_clkdiv (*(volatile uint32_t*)0x02000004)
+#define reg_uart_data (*(volatile uint32_t*)0x02000008)
+#define reg_leds (*(volatile uint32_t*)0x03000000)
+
+void main()
+{
+	reg_uart_clkdiv = 104;
+	reg_leds = 1;
+	reg_uart_data = 'H';
+	reg_leds = 2;
+	reg_uart_data = 'e';
+	reg_leds = 3;
+	reg_uart_data = 'l';
+	reg_leds = 4;
+	reg_uart_data = 'l';
+	reg_leds = 5;
+	reg_uart_data = 'o';
+	reg_leds = 6;
+	reg_uart_data = '\r';
+	reg_leds = 7;
+	reg_uart_data = '\n';
+	reg_leds = 8;
+}
+

picosoc/start.s

@@ -0,0 +1,38 @@
+.section .text
+
+start:
+addi x1, zero, 0
+addi x2, zero, 0
+addi x3, zero, 0
+addi x4, zero, 0
+addi x5, zero, 0
+addi x6, zero, 0
+addi x7, zero, 0
+addi x8, zero, 0
+addi x9, zero, 0
+addi x10, zero, 0
+addi x11, zero, 0
+addi x12, zero, 0
+addi x13, zero, 0
+addi x14, zero, 0
+addi x15, zero, 0
+addi x16, zero, 0
+addi x17, zero, 0
+addi x18, zero, 0
+addi x19, zero, 0
+addi x20, zero, 0
+addi x21, zero, 0
+addi x22, zero, 0
+addi x23, zero, 0
+addi x24, zero, 0
+addi x25, zero, 0
+addi x26, zero, 0
+addi x27, zero, 0
+addi x28, zero, 0
+addi x29, zero, 0
+addi x30, zero, 0
+addi x31, zero, 0
+
+li sp, 4*256
+call main
+j start