>..Could you please share info about head driving signals ? What head -
>..from what printer ?
Hi Daniel,
I'm using CX4200/CX4800 head in my printer and only documents that I've is service manual plus hundreds of Epson/Seiko patents. I found most of the information by doing experiment and reading patents.
I'll try to explain and later I'll upload some waveforms to clarify things. It can be seen as a difficult but in reality it is not.
It is not a known SPI signal as far as I know.
This head has 4 colors and each color has 90 nozzles. There're common signals used for all color "common" (Ramp signal) , "LE" (latch enable), Clock, NCHG (Charge signal), CH (waveform counter signal). Individual color has its own data signal. This head uses double edge clock as a clock of internal shift registers. You can change the clock and data simultaneously (inside head there is a delay circuit to avoid setup hold violation).
Each nozzle is represented by 2bits (4 different drop size) so if you have 90 nozzles then we need to send 180 bits just for nozzles data remaining 32 bits are used for waveform (ramp waveform) select. With 32 waveform control bits we can select 8 different waveforms (32/4(drop size)) for all 90 nozzles.
The data format can be summarized as,
180bits nozzle data + 32 bits Waveform select data.
As a short example,
Data (010.....)
--
-- -- ............... data
-- -- --
- -- -- --........ clock
The "Common" signal is an analog ramp voltage centered ~20V goes up to ~30V and down to ~2V. The shape of waveform defines the droplet size.
Cheers,
Volkan
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