Nokia 5510 - DSP Repair Tool gsm

5510 DSP REPAIR TOOL boots a Nokia 5510 with a failed radio and flashes firmware with direct *.MP3 file support.

1. Introduction

I have been a Nokia 5510 fan for years.
At the end of the week, I had some Codex tokens left to burn,
so I decided to solve two problems with this phone.

The first is the radio module, which commonly fails.
The TEA5757 is no longer available in the right footprint.
When the tuner stops responding, the phone shuts down shortly after booting.

The second problem is the lack of direct *.MP3 file support.
You have to convert every track to *.LSE first.

I solved both problems by modifying the music module firmware.

2. Disabling the radio in firmware

The DSP firmware has no source code available.
I started by decompiling versions R060 and R061.
I split the *.A00 container into seven segments.
Then I separated the DSP code from tables and other data.

I found the routines controlling the TEA5757 in the code.
They drive the DATA, CLK, WREN and STATUS lines.
The tuner has no separate READY line or write acknowledgement.
The firmware checks it by writing and then reading back the frequency.

During SELFTEST, the firmware tunes the radio to 87.50 MHz.
The reading must fall between 87.40 MHz and 87.60 MHz.
With a failed tuner, the procedure ends with an error or timeout.

In the No Radio version, the test immediately returns code 3, meaning PASS.
I also bypassed hardware access to DATA, CLK, WREN and STATUS.
The firmware sends no frame to the tuner and does not wait for tuning.

I kept the original state machine and completion messages.
They return result 1 and detail code 0.
The rest of the software therefore receives a valid response.

3. MP3 file support

The DSP firmware already includes an MP3 decoder.
The problem lies in how it opens files stored in phone memory.
The original software searches for tracks with the *.LSE extension.

An LSE file contains 384 B of metadata and a 512 B LockStream header.
The actual MP3 data starts after them.
The firmware therefore skips the first 896 B of each track.

In the MP3 variant, I changed the format name from LSE to MP3.
I bypassed the metadata and LockStream header reads.
I also disabled the header parser and selected the existing MP3 decoder.

I changed the stream start from 0x0380 bytes to 0.
I also cleared the corresponding 0x01C0 word offset.
The decoder now receives data from the start of a regular *.MP3 file.

I applied the same patches to firmware R060 and R061.
They do not overlap with the changes that disable the radio.
This produced MP3 variants both with and without a working radio.

The MP3 variant recognises *.MP3 files instead of *.LSE. Do not mix both formats in the phone memory.

4. 5510 DSP REPAIR TOOL

Testing each firmware revision took many attempts.
Moving files between computers soon became inconvenient.
I therefore wrote my own DSP flashing tool.

5510 DSP REPAIR TOOL runs on Windows and Linux.
I used EXT_UI DSP Flash Tool as a reference.
I decompiled it and analysed how it communicates with the phone.

I also wrote a logger that records all traffic on the COM port.
I used it to capture communication between the original tool and a Nokia 5510.
The logs revealed the frame order, phone responses and timeout values.
I reproduced the protocol in the new program from those findings.

I tested the x86 build on Windows XP and Windows 11.
On Windows 11, I had to disable Microsoft Defender SmartScreen for the x64 build.
The relevant option is called “Check apps and files”.
You can find it in the reputation-based protection settings.
Turn this option back on after flashing.

I distribute the Linux version as a *.deb package.
I tested it on Ubuntu and Linux Mint.
The package requires python3 3.10 or newer.
The interface uses python3-pyqt6 6.5 or python3-pyqt5 5.15.
Serial communication requires python3-serial 3.5 or newer.
Your package manager will install the dependencies with the program.

You can find the program and firmware files in:

5. Flashing the phone

5.1. What you need

Prepare:

• a Nokia 5510 with a battery and charger,
• an FBUS service cable with the TX and RX wires swapped,
• a computer with a COM port or a USB-to-RS232 adapter,
• the correct 5510 DSP REPAIR TOOL version for your system.

The program already includes the firmware files.
You do not need the separate archive when using 5510 DSP REPAIR TOOL.

5.2. Connecting the phone

Start the program and select the correct COM port.
Connect the FBUS cable and insert the battery.
Do not turn on the phone.
Then connect the charger.
When the battery charging icon appears, click Selftest.

If an error appears, disconnect the charger.
Remove the battery and disconnect the FBUS cable.
Reconnect everything in the same order.

With a failed radio, the SELFTEST result should look like this:

SELFTEST hardware results: DSP=3 (PASS), NAND=3 (PASS), Radio=0 (FAIL), AIC=3 (PASS), USB=3 (PASS)

Click Read from phone to read Product Information.
Click Save to file to save the data.

5.3. Choosing firmware

Leave initdisk_R060.a00 selected in the InitDisk list.
Choose the firmware you want to flash from the InitData list.

Both R060 and R061 variants should work with every Nokia 5510.
Choose the version already installed or update the phone to R061.

Original files:

• InitData_R060.a00 - R060 with a working radio and LSE support,
• InitData_R061.a00 - R061 with a working radio and LSE support.

Modified R060 variants:

• InitData_R060_mp3.a00 - working radio and MP3 support,
• InitData_R060_mp3_noradio.a00 - MP3 support with the radio disabled,
• InitData_R060_noradio.a00 - radio disabled with LSE support retained.

Modified R061 variants:

• InitData_R061_mp3.a00 - working radio and MP3 support,
• InitData_R061_mp3_noradio.a00 - MP3 support with the radio disabled,
• InitData_R061_noradio.a00 - radio disabled with LSE support retained.

For my phone with a failed radio, I used InitData_R061_mp3_noradio.a00.

5.4. Flashing the firmware

Disconnect the charger again before flashing.
Remove the battery and disconnect the FBUS cable.
Then connect the cable, insert the battery and connect the charger.

Wait for the battery charging icon.
Click Start, read the warning and accept it.
Flashing should take about 15 minutes.

Do not disconnect the phone or the charger while flashing.

When flashing is complete, disconnect the charger.
Remove the battery and disconnect the FBUS cable.
Reconnect everything and wait for the battery charging icon.
Click Write to phone to write the Product Information you read earlier.

Finally, run Selftest again.
After installing a No Radio variant, the result should look like this:

SELFTEST hardware results: DSP=3 (PASS), NAND=3 (PASS), Radio=3 (PASS), AIC=3 (PASS), USB=3 (PASS)

The Radio=3 (PASS) result means the firmware skipped the failed radio test.

6. Summary

I achieved both goals I set at the start of this project.
The Nokia 5510 now boots again despite its failed radio.
The MP3 variant plays regular *.MP3 files without converting them to LSE.

Along the way, I also created 5510 DSP REPAIR TOOL for Windows and Linux.
It flashes the DSP, runs SELFTEST, and reads and writes Product Information.
It also checks the phone responses while transferring data.

Do you have questions or suggestions, or would you like to report an error?
Write to me.

7. Download

x86 and x64 builds with firmware files.
SHA-256:

56c4c6ee44aa106b78e5a48ae4b467d54b41538e8f77b60492ce5a95cf0ab6fb

Package for Ubuntu, Linux Mint and compatible distributions.
SHA-256:

1ac1261929fdf48829669ad00597f5d01a8f872d02ee6262acad9dcb9488776e

Modified firmware without the program.
The archive contains MP3, No Radio and MP3 + No Radio variants.
You can also use them with the original EXT_UI DSP Flash Tool.
SHA-256:

285208e75b99ae438c1dd6e8aa2929c5f306e64643f8e9a69bd3eaa042bd12fa

I provide the program and firmware without warranty. You use them at your own risk.
I am not responsible for damage to hardware or software, or for data loss.