FreeCalypso > hg > freecalypso-hwlab
comparison eeproms/dumps/FT232R-notes @ 48:af70c59654ed
EEPROM dumps moved into eeproms/dumps and properly annotated
| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Mon, 22 Apr 2019 21:36:48 +0000 |
| parents | |
| children | 4e13c90c1405 |
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| 47:2c092eb1621b | 48:af70c59654ed |
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| 1 Unlike FT2232x devices with external EEPROMs, an FT232R device is not expected | |
| 2 to ever have a blank EEPROM in normal usage: these chips have their EEPROM | |
| 3 built in, and FTDI ships them with this internal EEPROM already programmed. | |
| 4 It may be possible to create a "blank" EEPROM by explicitly programming 0xFFFF | |
| 5 into every word, but it would be an unnatural scenario, and I (Mother Mychaela) | |
| 6 do not currently have an FT232R device on which I can experiment: I don't have | |
| 7 an FT232R device which is not valuable and which is not already bricked. | |
| 8 | |
| 9 I have read out the EEPROM content from the two specimen I did have available: | |
| 10 FT232R-specimen1 came from a no-name ebay-sourced FT232RL breakout board; | |
| 11 FT232R-specimen2 came from George UberWaves' "FTDI Professional" USB-serial | |
| 12 cable with OsmocomBB branding. Specimen 2 is probably a genuine FT232RL chip | |
| 13 (I remember George telling me that he went out of his way to procure genuine | |
| 14 FTDI chips after having been burned by FTDI's Winblows drivers screwing around | |
| 15 with close-but-not-perfect clones), but specimen 1 is suspected to be one of | |
| 16 those less-than-perfect clones: the serial number string was programmed to | |
| 17 "00000000", whereas FTDI supposedly program true per-unit serial numbers. | |
| 18 | |
| 19 The only diffs between FT232R-specimen1 and FT232R-specimen2 are the just- | |
| 20 mentioned serial number string (specimen 2 has it set to "A9031HG6", which looks | |
| 21 like a real per-unit serial number), two non-understood "garbage" words after | |
| 22 the last string, and of course the checksum. | |
| 23 | |
| 24 The unit that was specimen 1 (the suspected fake) is now bricked: when I tried | |
| 25 to program my own EEPROM config generated with ftee-gen232r, the resulting | |
| 26 EEPROM content became a bitwise AND between the previous image and the new one, | |
| 27 as if the "EEPROM" is not really an erasable memory, but one of OTP kind where | |
| 28 ones can be turned into zeros, but not the other way around. I am not willing | |
| 29 to experiment on the specimen 2 chip because it is part of a valuable cable | |
| 30 assembly which I don't want to risk bricking, so I will need to order more | |
| 31 sacrificial hardware and wait for it to arrive before I can experiment further. |