We've replaced our MR16s and MR24s with MR32s and have no official use for the hardware due to Meraki's cloud licensing. I've got OpenWRT running on a 16 and thought I would get this topic started to see if it goes anywhere.
The PCB is labeled UART and utilizes the same pinout as the MR12/16 devices. So I am able to provide some info on the unit.
PIN 1 has a white arrow
P1->empty (VCC)
P2->RX
P3->TX
P4->GND
Stock Boot
U-Boot 2010.06-00036-g4e1a276 Meraki MR24 (May 11 2012 - 16:57:49)
CPU: AMCC PowerPC UNKNOWN (PVR=12c41c83) at 800 MHz (PLB=200 OPB=100 EBC=100)
Bootstrap Option H - Boot ROM Location I2C (Addr 0x52), booting from NAND
32 kB I-Cache 32 kB D-Cache
Board: MR24 - Meraki MR24 Cloud Managed Access Point
============================
BoardID: 0 0
POE-PWR_DET Status: 0
ADAPTER_DET Status: 1
Reset Button Status: 1
============================
SDR0_PERCLK=0x40000300
I2C: ready
DRAM: 128 MiB
I2C write: failed 4
NAND: 32 MiB
*** Warning - bad CRC or NAND, using default environment
Configure Max Payload 256B
PCIE0: successfully set as root-complex
03 00 168c 0030 0280 ff
02 02 111d 8039 0604 00
04 00 168c 0030 0280 ff
02 03 111d 8039 0604 00
01 00 111d 8039 0604 00
I2C read: failed 4
I2C write: failed 4
I2C read: failed 4
I2C read: failed 4
I2C write: failed 4
Net: ppc_4xx_eth0
RESET is un-pushed
Set serverpath and run meraki_netboot to netboot
Hit any key to stop autoboot: 0
Creating 1 MTD partitions on "nand0":
0x000000180000-0x000002000000 : "mtd=2"
UBI: attaching mtd1 to ubi0
UBI: physical eraseblock size: 16384 bytes (16 KiB)
UBI: logical eraseblock size: 15872 bytes
UBI: smallest flash I/O unit: 512
UBI: sub-page size: 256
UBI: VID header offset: 256 (aligned 256)
UBI: data offset: 512
UBI: attached mtd1 to ubi0
UBI: MTD device name: "mtd=2"
UBI: MTD device size: 30 MiB
UBI: number of good PEBs: 1952
UBI: number of bad PEBs: 0
UBI: max. allowed volumes: 92
UBI: wear-leveling threshold: 4096
UBI: number of internal volumes: 1
UBI: number of user volumes: 4
UBI: available PEBs: 266
UBI: total number of reserved PEBs: 1686
UBI: number of PEBs reserved for bad PEB handling: 19
UBI: max/mean erase counter: 344/276
Volume part1 found at volume id 0
read 0 bytes from volume 0 to c00000(buf address)
Read [8983552] bytes
## Booting kernel from Legacy Image at 00c10000 ...
Image Name: Linux-3.4.106+
Created: 2015-09-21 21:46:57 UTC
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 1550370 Bytes = 1.5 MiB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
## Loading init Ramdisk from Legacy Image at 00e00000 ...
Image Name: Simple Ramdisk Image
Created: 2015-09-21 21:47:12 UTC
Image Type: PowerPC Linux RAMDisk Image (lzma compressed)
Data Size: 5205373 Bytes = 5 MiB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
## Flattened Device Tree blob at 00c00400
Booting using the fdt blob at 0xc00400
Uncompressing Kernel Image ... OK
Loading Ramdisk to 07677000, end 07b6dd7d ... OK
[ 0.000000] Using PowerPC 44x Platform machine description
[ 0.000000] Linux version 3.4.106+ (meraki@buildbot104.meraki.com) (gcc version 4.8.3 (GCC) ) #4 Mon Sep 21 14:46:48 PDT 2015
[ 0.000000] Found initrd at 0xc7677000:0xc7b6dd7d
[ 0.000000] Zone PFN ranges:
[ 0.000000] DMA 0x00000000 -> 0x00002000
[ 0.000000] Normal empty
[ 0.000000] Movable zone start PFN for each node
[ 0.000000] Early memory PFN ranges
[ 0.000000] 0: 0x00000000 -> 0x00002000
[ 0.000000] MMU: Allocated 1088 bytes of context maps for 255 contexts
[ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 8176
[ 0.000000] Kernel command line: root=/dev/ram console=ttyS0,115200 ubi.mtd=ubi MERAKI_BOARD=mr24 mtdoops.mtddev=oops
[ 0.000000] PID hash table entries: 512 (order: -3, 2048 bytes)
[ 0.000000] Dentry cache hash table entries: 16384 (order: 2, 65536 bytes)
[ 0.000000] Inode-cache hash table entries: 8192 (order: 1, 32768 bytes)
[ 0.000000] Memory: 122208k/131072k available (2960k kernel code, 8864k reserved, 176k data, 91k bss, 160k init)
[ 0.000000] Kernel virtual memory layout:
[ 0.000000] * 0xfffdc000..0xffffc000 : fixmap
[ 0.000000] * 0xfd600000..0xfe000000 : consistent mem
[ 0.000000] * 0xfd600000..0xfd600000 : early ioremap
[ 0.000000] * 0xd1000000..0xfd600000 : vmalloc & ioremap
[ 0.000000] SLUB: Genslabs=15, HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] NR_IRQS:512 nr_irqs:512 16
[ 0.000000] UIC0 (32 IRQ sources) at DCR 0xc0
[ 0.000000] UIC1 (32 IRQ sources) at DCR 0xd0
[ 0.000000] UIC2 (32 IRQ sources) at DCR 0xe0
[ 0.000000] UIC3 (32 IRQ sources) at DCR 0xf0
[ 0.000000] clocksource: timebase mult[1400000] shift[24] registered
[ 0.000067] pid_max: default: 32768 minimum: 301
[ 0.000241] Mount-cache hash table entries: 2048
[ 0.003010] devtmpfs: initialized
[ 0.003533] NET: Registered protocol family 16
[ 0.005720] 256k L2-cache enabled
[ 0.005808] PCIE0: Checking link...
[ 0.005815] PCIE0: Device detected, waiting for link...
[ 0.005824] PCIE0: link is up !
[ 0.110621] PCI host bridge /plb/pciex@d00000000 (primary) ranges:
[ 0.110647] MEM 0x0000000e00000000..0x0000000e7fffffff -> 0x0000000080000000
[ 0.110662] MEM 0x0000000f00000000..0x0000000f000fffff -> 0x0000000000000000
[ 0.110676] IO 0x0000000f80000000..0x0000000f8000ffff -> 0x0000000000000000
[ 0.110690] Removing ISA hole at 0x0000000f00000000
[ 0.110704] 4xx PCI DMA offset set to 0x00000000
[ 0.110712] 4xx PCI DMA window base to 0x0000000000000000
[ 0.110720] DMA window size 0x0000000080000000
[ 0.110737] /plb/pciex@d00000000: Legacy ISA memory support enabled
[ 0.110756] PCIE0: successfully set as root-complex
[ 0.111148] gpiochip_add: registered GPIOs 224 to 255 on device: /plb/opb/gpio@ef600b00
[ 0.111400] PCI: Probing PCI hardware
[ 0.111563] PCI host bridge to bus 0000:40
[ 0.111580] pci_bus 0000:40: root bus resource [io 0x0000-0xffff]
[ 0.111596] pci_bus 0000:40: root bus resource [mem 0xe00000000-0xe7fffffff] (bus address [0x80000000-0xffffffff])
[ 0.111709] PCI: Hiding 4xx host bridge resources 0000:40:00.0
[ 0.111949] pci 0000:40:00.0: PCI bridge to [bus 41-7f]
[ 0.111988] pci 0000:41:00.0: bridge configuration invalid ([bus 02-04]), reconfiguring
[ 0.112363] pci 0000:41:00.0: PCI bridge to [bus 42-ff]
[ 0.112410] pci 0000:42:02.0: bridge configuration invalid ([bus 03-03]), reconfiguring
[ 0.112428] pci 0000:42:03.0: bridge configuration invalid ([bus 04-04]), reconfiguring
[ 0.112725] pci 0000:42:02.0: PCI bridge to [bus 43-ff]
[ 0.113122] pci 0000:42:03.0: PCI bridge to [bus 44-ff]
[ 0.114685] pci 0000:40:00.0: BAR 8: assigned [mem 0xe00000000-0xe001fffff]
[ 0.114702] pci 0000:40:00.0: BAR 9: assigned [mem 0xe00200000-0xe003fffff pref]
[ 0.114719] pci 0000:41:00.0: BAR 8: assigned [mem 0xe00000000-0xe001fffff]
[ 0.114733] pci 0000:41:00.0: BAR 9: assigned [mem 0xe00200000-0xe003fffff pref]
[ 0.114749] pci 0000:42:02.0: BAR 8: assigned [mem 0xe00000000-0xe000fffff]
[ 0.114763] pci 0000:42:02.0: BAR 9: assigned [mem 0xe00200000-0xe002fffff pref]
[ 0.114777] pci 0000:42:03.0: BAR 8: assigned [mem 0xe00100000-0xe001fffff]
[ 0.114791] pci 0000:42:03.0: BAR 9: assigned [mem 0xe00300000-0xe003fffff pref]
[ 0.114807] pci 0000:43:00.0: BAR 0: assigned [mem 0xe00000000-0xe0001ffff 64bit]
[ 0.114829] pci 0000:43:00.0: BAR 6: assigned [mem 0xe00200000-0xe0020ffff pref]
[ 0.114843] pci 0000:42:02.0: PCI bridge to [bus 43-43]
[ 0.114857] pci 0000:42:02.0: bridge window [mem 0xe00000000-0xe000fffff]
[ 0.114871] pci 0000:42:02.0: bridge window [mem 0xe00200000-0xe002fffff pref]
[ 0.114889] pci 0000:44:00.0: BAR 0: assigned [mem 0xe00100000-0xe0011ffff 64bit]
[ 0.114910] pci 0000:44:00.0: BAR 6: assigned [mem 0xe00300000-0xe0030ffff pref]
[ 0.114922] pci 0000:42:03.0: PCI bridge to [bus 44-44]
[ 0.114936] pci 0000:42:03.0: bridge window [mem 0xe00100000-0xe001fffff]
[ 0.114949] pci 0000:42:03.0: bridge window [mem 0xe00300000-0xe003fffff pref]
[ 0.114964] pci 0000:41:00.0: PCI bridge to [bus 42-44]
[ 0.114977] pci 0000:41:00.0: bridge window [mem 0xe00000000-0xe001fffff]
[ 0.114991] pci 0000:41:00.0: bridge window [mem 0xe00200000-0xe003fffff pref]
[ 0.115006] pci 0000:40:00.0: PCI bridge to [bus 41-7f]
[ 0.115018] pci 0000:40:00.0: bridge window [mem 0xe00000000-0xe001fffff]
[ 0.115032] pci 0000:40:00.0: bridge window [mem 0xe00200000-0xe003fffff pref]
[ 0.119737] bio: create slab <bio-0> at 0
[ 0.121062] Switching to clocksource timebase
[ 0.122976] NET: Registered protocol family 2
[ 0.129839] IP route cache hash table entries: 4096 (order: 0, 16384 bytes)
[ 0.130118] TCP established hash table entries: 4096 (order: 1, 32768 bytes)
[ 0.130245] TCP bind hash table entries: 4096 (order: 0, 16384 bytes)
[ 0.130310] TCP: Hash tables configured (established 4096 bind 4096)
[ 0.130320] TCP: reno registered
[ 0.130332] UDP hash table entries: 1024 (order: 0, 16384 bytes)
[ 0.130389] UDP-Lite hash table entries: 1024 (order: 0, 16384 bytes)
[ 0.130592] NET: Registered protocol family 1
[ 0.130808] Unpacking initramfs...
[ 4.734697] Freeing initrd memory: 5104k freed
[ 5.085330] msgmni has been set to 248
[ 5.095778] io scheduler noop registered
[ 5.095793] io scheduler deadline registered (default)
[ 5.118529] Serial: 8250/16550 driver, 1 ports, IRQ sharing enabled
[ 5.150727] serial8250.0: ttyS0 at MMIO 0x4ef600400 (irq = 21) is a U6_16550A
[ 5.738621] console [ttyS0] enabled
[ 5.754225] 4ef600400.serial: ttyS0 at MMIO 0x4ef600400 (irq = 21) is a 16550
[ 5.769439] Trying to register dev faulty etc
[ 5.802074] NAND device: Manufacturer ID: 0xad, Chip ID: 0x75 (Hynix NAND 32MiB 3,3V 8-bit)
[ 5.810413] Scanning device for bad blocks
[ 5.920759] 4 ofpart partitions found on MTD device 4e4000000.ndfc.nand
[ 5.927395] Creating 4 MTD partitions on "4e4000000.ndfc.nand":
[ 5.933302] 0x000000000000-0x000000170000 : "firmware"
[ 5.949329] 0x000000170000-0x000000180000 : "oops"
[ 5.963656] mtdoops: Attached to MTD device 1
[ 5.978216] 0x000000180000-0x000002000000 : "ubi"
[ 5.999544] 0x000000000000-0x000002000000 : "all"
[ 6.033127] UBI: attaching mtd2 to ubi0
[ 6.036965] UBI: physical eraseblock size: 16384 bytes (16 KiB)
[ 6.043070] UBI: logical eraseblock size: 15872 bytes
[ 6.048355] UBI: smallest flash I/O unit: 512
[ 6.052957] UBI: sub-page size: 256
[ 6.057558] UBI: VID header offset: 256 (aligned 256)
[ 6.063375] UBI: data offset: 512
[ 6.237779] UBI: max. sequence number: 539115
[ 6.268811] UBI: attached mtd2 to ubi0
[ 6.272599] UBI: MTD device name: "ubi"
[ 6.277367] UBI: MTD device size: 30 MiB
[ 6.282228] UBI: number of good PEBs: 1952
[ 6.286914] UBI: number of bad PEBs: 0
[ 6.291343] UBI: number of corrupted PEBs: 0
[ 6.295770] UBI: max. allowed volumes: 92
[ 6.300280] UBI: wear-leveling threshold: 4096
[ 6.304968] UBI: number of internal volumes: 1
[ 6.309395] UBI: number of user volumes: 4
[ 6.313825] UBI: available PEBs: 247
[ 6.318424] UBI: total number of reserved PEBs: 1705
[ 6.323372] UBI: number of PEBs reserved for bad PEB handling: 38
[ 6.329441] UBI: max/mean erase counter: 344/276
[ 6.334043] UBI: image sequence number: 1992864020
[ 6.338998] UBI: background thread "ubi_bgt0d" started, PID 386
[ 6.407247] PPC 4xx OCP EMAC driver, version 3.54
[ 6.412345] MAL v2 /plb/mcmal, 1 TX channels, 1 RX channels
[ 6.427522] RGMII /plb/opb/emac-rgmii@ef601500 initialized with MDIO support
[ 6.434989] TAH /plb/opb/emac-tah@ef601350 initialized
[ 6.444130] /plb/opb/emac-rgmii@ef601500: input 0 in RGMII mode
[ 6.459289] eth0: EMAC-0 /plb/opb/ethernet@ef600c00, MAC 00:01:73:01:23:41
[ 6.466187] eth0: found Atheros 8305 Gigabit Ethernet PHY (0x01)
[ 6.480232] input: gpio_keys_polled.6 as /devices/plb.0/opb.3/gpio_keys_polled.6/input/input0
[ 6.502956] i2c /dev entries driver
[ 6.518655] ibm-iic 4ef600700.i2c: using standard (100 kHz) mode
[ 6.530865] rtc-m41t80 0-0068: chip found, driver version 0.05
[ 6.538552] rtc-m41t80 0-0068: read error
[ 6.545047] rtc-m41t80 0-0068: rtc core: registered m41t80 as rtc0
[ 6.553019] rtc-m41t80 0-0068: Can't clear HT bit
[ 6.560046] rtc-m41t80: probe of 0-0068 failed with error -5
[ 6.576204] ibm-iic 4ef600800.i2c: using standard (100 kHz) mode
[ 6.589979] lm90 0-004c: Register 0x4 read failed (-121)
[ 6.595319] lm90 0-004c: Failed to read convrate register!
[ 6.602760] lm90 0-004c: Register 0x3 read failed (-121)
[ 6.608057] lm90 0-004c: Initialization failed!
[ 7.451090] booke_wdt: powerpc book-e watchdog driver loaded
[ 7.487620] oprofile: using timer interrupt.
[ 7.492112] TCP: bic registered
[ 7.495245] TCP: cubic registered
[ 7.498545] TCP: westwood registered
[ 7.502113] TCP: htcp registered
[ 7.505332] NET: Registered protocol family 17
[ 7.530545] /disk/instance1/meraki/buildslave/build_powerpc-upload-r23/build/linux-3.4/drivers/rtc/hctosys.c: unable to open rtc device (rtc0)
[ 7.543347] ### of_selftest(): No testcase data in device tree; not running tests
[ 7.550937] devtmpfs: mounted
[ 7.556752] Freeing unused kernel memory: 160k freed
[ 7.564662] Made it into bootsh: Sep 21 2015 14:37:58
[ 7.569859] bootsh build 23-177858
[ 7.586087] UBIFS: recovery needed
[ 7.608687] UBIFS: recovery completed
[ 7.612363] UBIFS: mounted UBI device 0, volume 3, name "storage"
[ 7.618438] UBIFS: file system size: 8237568 bytes (8044 KiB, 7 MiB, 519 LEBs)
[ 7.625812] UBIFS: journal size: 412672 bytes (403 KiB, 0 MiB, 26 LEBs)
[ 7.632922] UBIFS: media format: w4/r0 (latest is w4/r0)
[ 7.638729] UBIFS: default compressor: lzo
[ 7.642813] UBIFS: reserved for root: 389080 bytes (379 KiB)
init started: BusyBox v1.20.2 (2015-09-21 13:46:14 PDT)
[ 7.775551] Sat Jan 1 00:00:00 UTC 2000
WARNING! THIS CONSOLE IS LOGGED! UNAUTHORIZED ACCESS FORBIDDEN!
<Meraki> [ 7.869954] sh: write error: Device or resource busy
[ 7.875034] /etc/init.d/S10boot: line 201: can't create /sys/class/gpio/gpio240/direction: nonexistent directory
[ 7.976531] sysctl: error: 'vm.extfrag_threshold' is an unknown key
[ 8.063560] wired0: link is down
[ 8.216085] sysctl -w vm.panic_on_oom=2
[ 8.226773] vm.panic_on_oom = 2
[ 8.438708] click: starting router thread pid 689 (c6172200)
[ 8.512634] elts_meraki: module license 'unspecified' taints kernel.
[ 8.749820] Single synchronous check for reset
[ 8.772413]
[ 8.780298] boot 38 build 23-177858 board powerpc mac 00:18:0A:27:2D:F2
[ 8.791316] Module: dummy .text=0xd1120000 .data=0xd1120540 .bss=
[ 8.791329] Module: proclikefs .text=0xd1138000 .data= .bss=0xd1138d40
[ 8.791335] Module: merakiclick .text=0xd5b40000 .data=0xd5c4611c .bss=0xd5c465a0
[ 8.791341] Module: elts_meraki .text=0xd6034000 .data=0xd62324a4 .bss=0xd6232c0c
[ 20.056828] adf: module license 'Proprietary' taints kernel.
[ 20.068457] asf: module license 'Proprietary' taints kernel.
[ 20.100276] ath_hal: module license 'Proprietary' taints kernel.
[ 20.128504] ath_hal: 0.9.17.1 (AR5416, AR9380, DEBUG, REGOPS_FUNC, WRITE_EEPROM, 11D)
[ 20.147048] ath_dfs: module license 'Proprietary' taints kernel.
[ 20.155833] ath_dfs: Version 2.0.0
[ 20.155840] Copyright (c) 2005-2006 Atheros Communications, Inc. All Rights Reserved
[ 20.177669] ath_rate_atheros: module license 'Proprietary' taints kernel.
[ 20.186694] ath_rate_atheros: Copyright (c) 2001-2005 Atheros Communications, Inc, All Rights Reserved
[ 20.209137] ath_dev: module license 'Proprietary' taints kernel.
[ 20.229447] ath_dev: Copyright (c) 2001-2007 Atheros Communications, Inc, All Rights Reserved
[ 20.247984] ath_pktlog: module license 'unspecified' taints kernel.
[ 20.314162] ath_pci: 9.5.5.36 (Atheros/multi-bss)
[ 20.318999] __ath_attach: Set global_scn[0]
[ 20.323218] ACBKMinfree = 48
[ 20.326085] ACBEMinfree = 32
[ 20.328954] ACVIMinfree = 16
[ 20.331827] ACVOMinfree = 0
[ 20.334613] CABMinfree = 48
[ 20.337395] UAPSDMinfree = 0
[ 20.537255] ath_get_caps[6084] rx chainmask mismatch actual 7 sc_chainmak 0
[ 20.544218] ath_get_caps[6058] tx chainmask mismatch actual 7 sc_chainmak 0
[ 20.577076] wifi0: Atheros 9380: mem=0xe00000000, irq=19 hw_base=0xd6780000
[ 20.584194] __ath_attach: Set global_scn[1]
[ 20.588362] ACBKMinfree = 48
[ 20.591244] ACBEMinfree = 32
[ 20.594115] ACVIMinfree = 16
[ 20.596983] ACVOMinfree = 0
[ 20.599766] CABMinfree = 48
[ 20.602553] UAPSDMinfree = 0
[ 20.789803] ath_get_caps[6084] rx chainmask mismatch actual 7 sc_chainmak 0
[ 20.796772] ath_get_caps[6058] tx chainmask mismatch actual 7 sc_chainmak 0
[ 20.817332] wifi1: Atheros 9380: mem=0xe00100000, irq=20 hw_base=0xd67c0000
[ 20.901522] brain: unloading click config
[ 20.905717] brain: spring cleaning pages
[ 20.946464] wlan_vap_create : enter. devhandle=0xc60343a0, opmode=IEEE80211_M_HOSTAP, flags=0x0
[ 20.955555] wlan_vap_create : exit. devhandle=0xc60343a0, opmode=IEEE80211_M_HOSTAP, flags=0x0.
[ 21.395069] wlan_vap_create : enter. devhandle=0xc603c3a0, opmode=IEEE80211_M_HOSTAP, flags=0x0
[ 21.404156] wlan_vap_create : exit. devhandle=0xc603c3a0, opmode=IEEE80211_M_HOSTAP, flags=0x0.
I see old support for PPC 44x devices and no recent changes so maybe a lot of this work is already complete? Happy to help however I can.