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6 years, 11 months ago.
Trick to using SPI on MAX32630FTHR?
I am having a strange problem trying to use SPI on the board. I get SPI cycles with SCK and correct data on MOSI but the data on MISO is not read correctly. I wrote this very simple test program based on the mbed example.
/media/uploads/danjulio/main.cpp
This produces the following output. The first byte is what is output to MOSI. The second byte is what is read from MISO.
Am I doing something wrong or is there some issue with the SPI implementation for the MAX32630FTHR?
0x 0 : 0x80
0x 1 : 0x80
0x 2 : 0x81
0x 3 : 0x81
0x 4 : 0x82
0x 5 : 0x82
0x 6 : 0x83
0x 7 : 0x83
0x 8 : 0x84
0x 9 : 0x84
0x a : 0x85
0x b : 0x85
0x c : 0x86
0x d : 0x86
0x e : 0x87
0x f : 0x87
0x10 : 0x88
0x11 : 0x88
0x12 : 0x89
0x13 : 0x89
0x14 : 0x8a
0x15 : 0x8a
0x16 : 0x8b
0x17 : 0x8b
0x18 : 0x8c
0x19 : 0x8c
0x1a : 0x8d
0x1b : 0x8d
0x1c : 0x8e
0x1d : 0x8e
0x1e : 0x8f
0x1f : 0x8f
0x20 : 0x90
0x21 : 0x90
0x22 : 0x91
0x23 : 0x91
0x24 : 0x92
0x25 : 0x92
0x26 : 0x93
0x27 : 0x93
0x28 : 0x94
0x29 : 0x94
0x2a : 0x95
0x2b : 0x95
0x2c : 0x96
0x2d : 0x96
0x2e : 0x97
0x2f : 0x97
0x30 : 0x98
0x31 : 0x98
0x32 : 0x99
0x33 : 0x99
0x34 : 0x9a
0x35 : 0x9a
0x36 : 0x9b
0x37 : 0x9b
0x38 : 0x9c
0x39 : 0x9c
0x3a : 0x9d
0x3b : 0x9d
0x3c : 0x9e
0x3d : 0x9e
0x3e : 0x9f
0x3f : 0x9f
0x40 : 0xa0
0x41 : 0xa0
0x42 : 0xa1
0x43 : 0xa1
0x44 : 0xa2
0x45 : 0xa2
0x46 : 0xa3
0x47 : 0xa3
0x48 : 0xa4
0x49 : 0xa4
0x4a : 0xa5
0x4b : 0xa5
0x4c : 0xa6
0x4d : 0xa6
0x4e : 0xa7
0x4f : 0xa7
0x50 : 0xa8
0x51 : 0xa8
0x52 : 0xa9
0x53 : 0xa9
0x54 : 0xaa
0x55 : 0xaa
0x56 : 0xab
0x57 : 0xab
0x58 : 0xac
0x59 : 0xac
0x5a : 0xad
0x5b : 0xad
0x5c : 0xae
0x5d : 0xae
0x5e : 0xaf
0x5f : 0xaf
0x60 : 0xb0
0x61 : 0xb0
0x62 : 0xb1
0x63 : 0xb1
0x64 : 0xb2
0x65 : 0xb2
0x66 : 0xb3
0x67 : 0xb3
0x68 : 0xb4
0x69 : 0xb4
0x6a : 0xb5
0x6b : 0xb5
0x6c : 0xb6
0x6d : 0xb6
0x6e : 0xb7
0x6f : 0xb7
0x70 : 0xb8
0x71 : 0xb8
0x72 : 0xb9
0x73 : 0xb9
0x74 : 0xba
0x75 : 0xba
0x76 : 0xbb
0x77 : 0xbb
0x78 : 0xbc
0x79 : 0xbc
0x7a : 0xbd
0x7b : 0xbd
0x7c : 0xbe
0x7d : 0xbe
0x7e : 0xbf
0x7f : 0xbf
0x80 : 0xc0
0x81 : 0xc0
0x82 : 0xc1
0x83 : 0xc1
0x84 : 0xc2
0x85 : 0xc2
0x86 : 0xc3
0x87 : 0xc3
0x88 : 0xc4
0x89 : 0xc4
0x8a : 0xc5
0x8b : 0xc5
0x8c : 0xc6
0x8d : 0xc6
0x8e : 0xc7
0x8f : 0xc7
0x90 : 0xc8
0x91 : 0xc8
0x92 : 0xc9
0x93 : 0xc9
0x94 : 0xca
0x95 : 0xca
0x96 : 0xcb
0x97 : 0xcb
0x98 : 0xcc
0x99 : 0xcc
0x9a : 0xcd
0x9b : 0xcd
0x9c : 0xce
0x9d : 0xce
0x9e : 0xcf
0x9f : 0xcf
0xa0 : 0xd0
0xa1 : 0xd0
0xa2 : 0xd1
0xa3 : 0xd1
0xa4 : 0xd2
0xa5 : 0xd2
0xa6 : 0xd3
0xa7 : 0xd3
0xa8 : 0xd4
0xa9 : 0xd4
0xaa : 0xd5
0xab : 0xd5
0xac : 0xd6
0xad : 0xd6
0xae : 0xd7
0xaf : 0xd7
0xb0 : 0xd8
0xb1 : 0xd8
0xb2 : 0xd9
0xb3 : 0xd9
0xb4 : 0xda
0xb5 : 0xda
0xb6 : 0xdb
0xb7 : 0xdb
0xb8 : 0xdc
0xb9 : 0xdc
0xba : 0xdd
0xbb : 0xdd
0xbc : 0xde
0xbd : 0xde
0xbe : 0xdf
0xbf : 0xdf
0xc0 : 0xe0
0xc1 : 0xe0
0xc2 : 0xe1
0xc3 : 0xe1
0xc4 : 0xe2
0xc5 : 0xe2
0xc6 : 0xe3
0xc7 : 0xe3
0xc8 : 0xe4
0xc9 : 0xe4
0xca : 0xe5
0xcb : 0xe5
0xcc : 0xe6
0xcd : 0xe6
0xce : 0xe7
0xcf : 0xe7
0xd0 : 0xe8
0xd1 : 0xe8
0xd2 : 0xe9
0xd3 : 0xe9
0xd4 : 0xea
0xd5 : 0xea
0xd6 : 0xeb
0xd7 : 0xeb
0xd8 : 0xec
0xd9 : 0xec
0xda : 0xed
0xdb : 0xed
0xdc : 0xee
0xdd : 0xee
0xde : 0xef
0xdf : 0xef
0xe0 : 0xf0
0xe1 : 0xf0
0xe2 : 0xf1
0xe3 : 0xf1
0xe4 : 0xf2
0xe5 : 0xf2
0xe6 : 0xf3
0xe7 : 0xf3
0xe8 : 0xf4
0xe9 : 0xf4
0xea : 0xf5
0xeb : 0xf5
0xec : 0xf6
0xed : 0xf6
0xee : 0xf7
0xef : 0xf7
0xf0 : 0xf8
0xf1 : 0xf8
0xf2 : 0xf9
0xf3 : 0xf9
0xf4 : 0xfa
0xf5 : 0xfa
0xf6 : 0xfb
0xf7 : 0xfb
0xf8 : 0xfc
0xf9 : 0xfc
0xfa : 0xfd
0xfb : 0xfd
0xfc : 0xfe
0xfd : 0xfe
0xfe : 0xff
Question relating to:
2 Answers
6 years, 11 months ago.
The current version of the MAX32630FTHR board is shipping with the MAX32630 rev A2. These parts only support SPI mode 0. You can find the details in the errata which is available in the datasheet link on the product page: https://www.maximintegrated.com/en/products/digital/microcontrollers/MAX32630.html
6 years, 11 months ago.
SPI line MISO is Master In Slave out and is usually linked with a CS (Chip select) on the mating SPI device. Would you have such a pin on your external SPI device ? If yes, that pin should then be connected to a free GPIO pin on your mbed board and respectively you will need to toggle this CS pin to enable the SPI device for such communications. Often called Slave Select.
See the example here:
https://developer.mbed.org/handbook/SPI
Note line 4 and the use of the DigitalOut definition for cs(port pin); You will need to do the same. Proceed to test this configuration and post your results. If still no luck, then post more details on the SPI widget you are testing including wiring diagram.
---
Got it. When you monitor the traffic on MOSI - is this MOSI pin mated with the local MISO pin ? It will be worthwhile to review the MOSI pin without MISO connection and then again with the MISO pin connected.
Perhaps the MISO results are tainted due to the port sharing method used by this Maxim board. See the schematic to note the same SPI port pins are being used by port P4.x. Confirm that each of the P4.x block of pins are hi-z. Although not a believer of hacking up original tools, you could even cut the trace between the MISO for your SPI Master (P5.2) and the shared SPI Slave P4.6 pin to isolate the two traces.
Thanks for the reply Sanjiv. I have experience using SPI. I originally tried to communicate with a MAX31865 RTD temperature amplifier chip using a software controlled CS line. My application will ultimately have two SPI peripherals so I did not define CS in the SPI object enumeration. I could see that MOSI data to the slave was ok (and I was driving CS correctly). However the data seen by the CPU from MISO was incorrect (I could see using an oscilloscope that it was being correctly driven by the 31865). So I wrote this very basic program just to test the SPI driver. It has no CS signal because that is not needed. I simply loop MOSI back to MISO with a wire and view the transactions on the scope as well (they are correct). The CPU should see the data it drives out. However as you can see, this data is incorrect.
posted by 21 May 2017Good suggestions. Thank you. I had tried setting P4.6 to a DigitalIn with no luck. Upon your suggestion, I set all three secondary ports to inputs (P4.4, P4.5, P4.6) but it didn't change anything either. It's not clear where I could cut to physically disconnect those signals and I am hesitant to try that because I have only one board and my fat fingers would probably make a mess of it. If I do not tie MISO to MOSI then I always read 0xFF as the input.
I have found what appears to be MAX32630FTHR specific support code including SPI code. However I haven't tried to parse through it since it looks moderately complex and will require diving into the chip spec.
posted by 23 May 2017Dan - do you receive the same echo values if you change the SPI mode to be 0 ? Greg (works for Maxim) and he is noting that the silicon appears to be only supportive of SPI Mode 0 (not 1, 2, 3). Consider to change your code to SPI mode 0 and perform the MISO & MOSI connection to test. Curious on your results.
-
Change:
spi.format(8, 1);
to
spi.format(8, 0);
posted by 23 May 2017