nrf52: Add new flash algo for nRF52833 that improves flashing time.

More info about the flash algo improvements in:
- pyocd/FlashAlgo#68

As the improvement was achieved from a feature not present in all
members of the nRF52 family, the original nRF52832 flash algo stays
and this version for nRF52833 has been added along side it.

Could potentially be used for nRF52840 targets as well.

Author: microbit-carlos

source/family/nordic/nrf52/flash_blob.c

@@ -21,6 +21,7 @@
 
 #include "flash_blob.h"
 
+// This flash algo should work with all members of the nRF52 family
 static const uint32_t nRF52832AA_FLM[] = {
     0xE00ABE00, 0x062D780D, 0x24084068, 0xD3000040, 0x1E644058, 0x1C49D1FA, 0x2A001E52, 0x4770D1F2,
     0x47702000, 0x47702000, 0x4c2bb570, 0x60202002, 0x20014929, 0x60083108, 0x68284d28, 0xd00207c0,
@@ -32,6 +33,21 @@ static const uint32_t nRF52832AA_FLM[] = {
     0x40010404, 0x40010504, 0x6e524635, 0x00000000,
 };
 
+// Compiled from a fork of the pyocd/FlashAlgo repository (details in README):
+// https://github.com/microbit-foundation/FlashAlgo/commit/03f07e6d635903e7272860cea72c84c078088a1a
+// Compared to the nRF52832 version, this is about 25% faster using a new NVMC
+// register (READYNEXT) only present in nRF52820, nRF52833, and nRF52840.
+static const uint32_t nRF52833_flash_algo[] = {
+    0xE00ABE00,
+    0xf8d24a09, 0xf0133404, 0xd00b03ff, 0x2504f8d2, 0x4a06b142, 0x07d84906, 0x6011bf48, 0xf102085b,
+    0xd1f80204, 0xbf004770, 0x40010000, 0x40010600, 0x6e524635, 0x47702000, 0x47702000, 0x4c09b510,
+    0xf8c42302, 0x23013504, 0x350cf8c4, 0x3400f8d4, 0xd40207db, 0xffd4f7ff, 0x2000e7f8, 0x0504f8c4,
+    0xbf00bd10, 0x4001e000, 0x4c0bb510, 0xf1b02302, 0xf8c42f10, 0xbf263504, 0xf8c42301, 0xf8c43514,
+    0xf7ff0508, 0xf8d4ffbd, 0x07db3400, 0x2000d5f9, 0x0504f8c4, 0xbf00bd10, 0x4001e000, 0x4e0fb5f8,
+    0x088d2301, 0x3504f8c6, 0x1a874614, 0x682219e3, 0x3404601a, 0x3408f8d6, 0xd40207da, 0xffa0f7ff,
+    0x3d01e7f8, 0xf8d6d1f2, 0x07db3400, 0xf7ffd402, 0xe7f8ff97, 0xf8c62000, 0xbdf80504, 0x4001e000
+};
+
 /**
 * List of start and size for each size of flash sector
 * The size will apply to all sectors between the listed address and the next address
@@ -61,3 +77,22 @@ static const program_target_t flash_nrf52 = {
     .algo_blob = nRF52832AA_FLM,
     .program_buffer_size = 512 // should be USBD_MSC_BlockSize
 };
+
+static const program_target_t flash_nrf52833 = {
+    .init = 0x20000039,
+    .uninit = 0x2000003d,
+    .erase_chip = 0x20000041,
+    .erase_sector = 0x2000006d,
+    .program_page = 0x200000a1,
+    .verify = 0x0,
+    {
+        .breakpoint = 0x20000001,
+        .static_base = 0x200000e4,
+        .stack_pointer = 0x20000300
+    },
+    .program_buffer = 0x20000000 + 0x00000A00,
+    .algo_start = 0x20000000,
+    sizeof(nRF52833_flash_algo),
+    .algo_blob = nRF52833_flash_algo,
+    .program_buffer_size = 512 // should be USBD_MSC_BlockSize
+};

source/family/nordic/nrf52/target.c

@@ -64,7 +64,7 @@ target_cfg_t target_device_nrf52833 = {
     .flash_regions[0].start         = 0,
     .flash_regions[0].end           = KB(512),
     .flash_regions[0].flags         = kRegionIsDefault,
-    .flash_regions[0].flash_algo    = (program_target_t *) &flash_nrf52,
+    .flash_regions[0].flash_algo    = (program_target_t *) &flash_nrf52833,
     .ram_regions[0].start           = 0x20000000,
     .ram_regions[0].end             = 0x20020000,
     .erase_reset                    = 1,