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I have been looking for some solution how i can control LCD display, which is connected via USB.

My first result is that i will use MCP2210 -http://www.microchip.com/wwwproducts/Devices.aspx?product=MCP2210 (USB to SPI via HID class). For the developing i used python lib https://github.com/arachnidlabs/mcp2210. Controlling gpio or spi is ok, but speed of spi is not.

I read article about HID where i found out that it can send only 64b/us.

And here is my question, have anyone some solution how can I send commands for display via 64b packets ?

Thanks Mike

Michal Sládeček
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1 Answers1

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My driver is currently getting about 12kB/s (96kb/s) and the device appears to have a maximum speed of about 20kB/s based upon the time it takes from one SPI transfer (of 60 bytes) to when it will accept another (seems to be about 7ms). But if you mean 64 bytes per microsecond then I think you are quite mistaken. That would be 8 megabytes per second and there's no way that thing will ever come close to that, although I understand that some of the FTDI devices might.

A major problem with using HID for real data (which isn't interfacing with humans -- at least as input) is that you use interrupt URBs which are 64 bytes in length.

Daniel Santos
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  • thanks for your answer. I will try this later (If HID wouldn´t be ok) – Michal Sládeček Feb 14 '16 at 15:13
  • finally i got smaller delay around 7ms as you wrote. (via osciloscope [link](https://ctrlv.cz/shots/2016/02/24/8rIO.png). Smaller delay i can't get on. So i suggest that is the mcp's minimum. (Form basic operation on display is ok so I am using this... – Michal Sládeček Feb 24 '16 at 22:08
  • Cool! Is this MISO & MOSI that I'm seeing here? For the last few weeks I've been reworking things in my driver with the intention of releasing a v0.2, and this is basically what I'm putting in the new `README`: the driver performs at about 12kB/s and the device has a theoretical maximum throughput of 20kB/s as per [analysis](https://github.com/daniel-santos/mcp2210-linux/issues/11#issuecomment-47812048) by [mweal-ed](https://github.com/mweal-ed) (not mine). If you can elaborate a bit on this I would like to link this as well please. – Daniel Santos Feb 25 '16 at 23:43