How do i program an ESP32 or an ESP8266 module using assembly? I don't want to use arduino ide. I figured a way to program atmel chips with assembly. I wanted to learn how to program esp32 and esp8266 in assembly.
The tools can be easily found. I installed a pre-built tarball.
This is a mix of C and asm but you can do this all asm.
This is for an esp8266.
vectors.s
.section .init
.globl _start
_start:
call0 notmain
ill
.balign 0x100
.globl dummy
dummy:
ret.n
.balign 0x10
.globl PUT32
PUT32:
memw
s32i.n a3,a2,0
ret.n
.balign 0x10
.globl GET32
GET32:
memw
l32i.n a2,a2,0
ret.n
so.c
#define GPIO_ENSET 0x60000310
#define GPIO_OUTSET 0x60000304
#define GPIO_OUTCLR 0x60000308
#define IOMUX_GPIO2 0x60000838
void dummy ( unsigned int );
void PUT32 ( unsigned int, unsigned int );
unsigned GET32 ( unsigned int );
void notmain ( void )
{
unsigned int ra;
unsigned int rx;
ra=GET32(IOMUX_GPIO2);
ra&=(~0x130);
PUT32(IOMUX_GPIO2,ra);
PUT32(GPIO_ENSET,1<<2);
while(1)
{
PUT32(GPIO_OUTSET,1<<2);
for(rx=0;rx<800000;rx++) dummy(rx);
PUT32(GPIO_OUTCLR,1<<2);
for(rx=0;rx<800000;rx++) dummy(rx);
}
}
so.ld
MEMORY
{
bob : ORIGIN = 0x40100000, LENGTH = 0x1000
ted : ORIGIN = 0x3FFE8000, LENGTH = 0x1000
}
SECTIONS
{
.init : { *(.init*) } > bob
.literal : { *(.literal*) } > bob
.text : { *(.text*) } > bob
.rodata : { *(.rodata*) } > bob
.data : { *(.data*) } > ted
.bss : { *(.bss*) } > ted
}
build
xtensa-lx106-elf-as --warn --fatal-warnings vectors.s -o vectors.o
xtensa-lx106-elf-gcc -Wall -O2 -ffreestanding -c so.c -o so.o
xtensa-lx106-elf-ld -nostdlib -nostartfiles -T so.ld vectors.o so.o -o so.elf
xtensa-lx106-elf-objdump -D so.elf > so.list
xtensa-lx106-elf-objcopy so.elf so.bin -O binary
disassembly
Disassembly of section .init:
40100000 <_start>:
40100000: 001385 call0 4010013c <notmain>
...
40100100 <dummy>:
40100100: f00d ret.n
...
40100110 <PUT32>:
40100110: 0020c0 memw
40100113: 0239 s32i.n a3, a2, 0
40100115: f00d ret.n
...
40100120 <GET32>:
40100120: 0020c0 memw
40100123: 0228 l32i.n a2, a2, 0
40100125: f00d ret.n
Disassembly of section .literal:
40100128 <.literal>:
40100128: 0838 l32i.n a3, a8, 0
4010012a: 106000 and a6, a0, a0
4010012d: 03 .byte 0x3
4010012e: 046000 extui a6, a0, 0, 1
40100131: 03 .byte 0x3
40100132: 006000 rsil a0, 0
40100135: 35 .byte 0x35
40100136: 000c movi.n a0, 0
40100138: 0308 l32i.n a0, a3, 0
4010013a: 00 .byte 00
4010013b: 60 .byte 0x60
Disassembly of section .text:
4010013c <notmain>:
4010013c: e0c112 addi a1, a1, -32
4010013f: 61c9 s32i.n a12, a1, 24
40100141: fff9c1 l32r a12, 40100128 <GET32+0x8>
40100144: 7109 s32i.n a0, a1, 28
40100146: 0c2d mov.n a2, a12
40100148: 51d9 s32i.n a13, a1, 20
4010014a: 41e9 s32i.n a14, a1, 16
4010014c: 31f9 s32i.n a15, a1, 12
4010014e: fffd05 call0 40100120 <GET32>
40100151: cfae32 movi a3, 0xfffffecf
40100154: 103230 and a3, a2, a3
40100157: 0c2d mov.n a2, a12
40100159: fffb45 call0 40100110 <PUT32>
4010015c: fff421 l32r a2, 4010012c <GET32+0xc>
4010015f: 430c movi.n a3, 4
40100161: fffac5 call0 40100110 <PUT32>
40100164: fff3f1 l32r a15, 40100130 <GET32+0x10>
40100167: fff3d1 l32r a13, 40100134 <GET32+0x14>
4010016a: fff3e1 l32r a14, 40100138 <GET32+0x18>
4010016d: 430c movi.n a3, 4
4010016f: 0f2d mov.n a2, a15
40100171: fff9c5 call0 40100110 <PUT32>
40100174: 0c0c movi.n a12, 0
40100176: 0c2d mov.n a2, a12
40100178: cc1b addi.n a12, a12, 1
4010017a: fff845 call0 40100100 <dummy>
4010017d: f59cd7 bne a12, a13, 40100176 <notmain+0x3a>
40100180: 430c movi.n a3, 4
40100182: 202ee0 or a2, a14, a14
40100185: fff885 call0 40100110 <PUT32>
40100188: 0c0c movi.n a12, 0
4010018a: 0c2d mov.n a2, a12
4010018c: cc1b addi.n a12, a12, 1
4010018e: fff705 call0 40100100 <dummy>
40100191: f59cd7 bne a12, a13, 4010018a <notmain+0x4e>
40100194: fff546 j 4010016d <notmain+0x31>
And then due to how this was done, you can't use esptool.py to prep the file, so I made my own, taking the output here:
hexdump -C so.bin
00000000 85 13 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000100 0d f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000110 c0 20 00 39 02 0d f0 00 00 00 00 00 00 00 00 00 |. .9............|
00000120 c0 20 00 28 02 0d f0 00 38 08 00 60 10 03 00 60 |. .(....8..`...`|
00000130 04 03 00 60 00 35 0c 00 08 03 00 60 12 c1 e0 c9 |...`.5.....`....|
00000140 61 c1 f9 ff 09 71 2d 0c d9 51 e9 41 f9 31 05 fd |a....q-..Q.A.1..|
00000150 ff 32 ae cf 30 32 10 2d 0c 45 fb ff 21 f4 ff 0c |.2..02.-.E..!...|
00000160 43 c5 fa ff f1 f3 ff d1 f3 ff e1 f3 ff 0c 43 2d |C.............C-|
00000170 0f c5 f9 ff 0c 0c 2d 0c 1b cc 45 f8 ff d7 9c f5 |......-...E.....|
00000180 0c 43 e0 2e 20 85 f8 ff 0c 0c 2d 0c 1b cc 05 f7 |.C.. .....-.....|
00000190 ff d7 9c f5 46 f5 ff |....F..|
00000197
turning it into this
hexdump -C so.esp.bin
00000000 e9 01 00 00 00 00 10 40 00 00 10 40 98 01 00 00 |.......@...@....|
00000010 85 13 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000110 0d f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00000120 c0 20 00 39 02 0d f0 00 00 00 00 00 00 00 00 00 |. .9............|
00000130 c0 20 00 28 02 0d f0 00 38 08 00 60 10 03 00 60 |. .(....8..`...`|
00000140 04 03 00 60 00 35 0c 00 08 03 00 60 12 c1 e0 c9 |...`.5.....`....|
00000150 61 c1 f9 ff 09 71 2d 0c d9 51 e9 41 f9 31 05 fd |a....q-..Q.A.1..|
00000160 ff 32 ae cf 30 32 10 2d 0c 45 fb ff 21 f4 ff 0c |.2..02.-.E..!...|
00000170 43 c5 fa ff f1 f3 ff d1 f3 ff e1 f3 ff 0c 43 2d |C.............C-|
00000180 0f c5 f9 ff 0c 0c 2d 0c 1b cc 45 f8 ff d7 9c f5 |......-...E.....|
00000190 0c 43 e0 2e 20 85 f8 ff 0c 0c 2d 0c 1b cc 05 f7 |.C.. .....-.....|
000001a0 ff d7 9c f5 46 f5 ff 00 00 00 00 00 00 00 00 ae |....F...........|
000001b0
I will let you figure that out, tool sources are available.
https://github.com/espressif/esptool
If this link stops working then search for "esptool.py" to hopefully find one.
Then flash it:
esptool.py --port /dev/ttyUSB5 write_flash -fm qio 0x00000 so.esp.bin
I am using a cheap nodemcu clone. I bought 5 of them for $15 on Amazon. Don't need extra wires/usb-uart, etc.
Changing these
for(rx=0;rx<800000;rx++)
to/from
for(rx=0;rx<400000;rx++)
and see the led blink rate change.
You can easily write this in only assembly by poking the few registers yourself.