What is the max SPI clock frequency of CFA835?
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CFA835 max SPI clock frequency
- Thread starter Rezaaa
- Start date
Hello,
Thanks for your question.
We have tested the CFA835 up to a SPI clock frequency of 15Mhz.
Please keep in mind that the CFA835 may not be able to process incoming data packets at that speed. Some time will need to be given between packets, otherwise the input data buffer will overflow.
The preferred method is to wait for a response acknowledge or error packet from the CFA835 before sending the next command packet.
Please let us know if you have any other questions.
Thanks for your question.
We have tested the CFA835 up to a SPI clock frequency of 15Mhz.
Please keep in mind that the CFA835 may not be able to process incoming data packets at that speed. Some time will need to be given between packets, otherwise the input data buffer will overflow.
The preferred method is to wait for a response acknowledge or error packet from the CFA835 before sending the next command packet.
Please let us know if you have any other questions.
Thank you CF Mark for your response.
I got good performance by setting the max SPI clock frequency to 10MHz
I do have couple of more questions, would you please review them and provide your response?
In our platform CFA835 is connected via SPI interface to a Linux host using spidev driver, the SPI data ready signal is connected to a GPIO.
I noticed when a command is sent to CFA835, there are data being sent out by CFA835 on MISO while host is transferring data on MOSI.
The data sent out by CFA835 are 0xff, 0x1d, 0xe7, 0x74 ...
1-What is the significance of these data sent out by CFA835, before receiving new command? Considering the response from previous command has been read by host.
After host sends command, it monitors the SPI data ready signal when it becomes active (low), host would try to read data as long as the data ready stays active.
2- I noticed there is always an extra byte at the start of the data CFA835 sends out. The correct response from CFA835 is after the first byte. Why there is an extra byte at the beginning of CFA835 response?
Thanks,
Reza
I got good performance by setting the max SPI clock frequency to 10MHz
I do have couple of more questions, would you please review them and provide your response?
In our platform CFA835 is connected via SPI interface to a Linux host using spidev driver, the SPI data ready signal is connected to a GPIO.
I noticed when a command is sent to CFA835, there are data being sent out by CFA835 on MISO while host is transferring data on MOSI.
The data sent out by CFA835 are 0xff, 0x1d, 0xe7, 0x74 ...
1-What is the significance of these data sent out by CFA835, before receiving new command? Considering the response from previous command has been read by host.
After host sends command, it monitors the SPI data ready signal when it becomes active (low), host would try to read data as long as the data ready stays active.
2- I noticed there is always an extra byte at the start of the data CFA835 sends out. The correct response from CFA835 is after the first byte. Why there is an extra byte at the beginning of CFA835 response?
Thanks,
Reza
My apologies for the delayed response.
1)
If there is packet data in the outgoing SPI buffer of the module it will be sent on MISO (the SPI INT pin (H1 Pin12) will also be pulled low)
If there is no data to send, the module will send the last data byte repeatedly on MISO.
It is up to the host/master device to separate out valid packets from junk data.
2)
It should not do so.
What version of the CFA835 firmware are you using?
1)
If there is packet data in the outgoing SPI buffer of the module it will be sent on MISO (the SPI INT pin (H1 Pin12) will also be pulled low)
If there is no data to send, the module will send the last data byte repeatedly on MISO.
It is up to the host/master device to separate out valid packets from junk data.
2)
It should not do so.
What version of the CFA835 firmware are you using?
I think it would be a good idea for you to upgrade firmware version. The last release has some SPI interface improvements that may fix that problem.
Can you please send an email to support@crystalfontz.com asking for CFA835 firmware version 1.8 ?
Can you please send an email to support@crystalfontz.com asking for CFA835 firmware version 1.8 ?
