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SPI Master Clock Speed
rabryn
Join Date: 12 Jun 18
Posts: 9
Posted: Thu, 2021-02-18 11:52
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Hello,

I am using the QCA4020's SPI master to communicate to a device that has a maximum SCLK frequency of 2MHz.  I'd like to operate the QCA4020's SPI master's SCLK at 500KHz or 1MHz.  I have the SPI master working and can see the SCLK and MOSI data on my logic analyzer, however, it seems I cannot reduce the SPI's SCLK frequency to an acceptable value.  If I set qapi_SPIM_Config_t's max_Slave_Freq_Hz to 100,000 it outputs at 50MHz.  If I set it to 20M I see 16.67MHz.

I assume 500KHz is too low and is simply not being recognized as a valid max_Slave_Freq_Hz.  Is it possible to reduce the QCA4020's SPI master's SCLK to a value less than 2MHz?  Is there a divider I can adjust somewhere?

Thank you,

Ryan

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Re: SPI Master Clock Speed
c_rpedad
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Join Date: 18 Jun 18
Location: San Jose
Posts: 317
Posted: Thu, 2021-02-25 15:53
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QCA4020 SPI supports clock frequency between 3MHz~48MHz.
The limitation is due to fixed 48MHz internal clock and the divider is 4 bits (0~`5) resulting in final clock between 48MHz~3MHz.

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