Hi,
I had never used the MSSP module in slave mode Before but I just had a play with two 18F25K20 devices, one as master and one as slave.
The master sends the letters "A" to "Z" and outputs both what it sends and what it recieves to the serial terminal.
The slave responds with the letters "Z" to "A". It outputs what it receives and what it sends to the serial terminal.
At this time I did not have time to implement and test the SS-line but apart from that it appears to work as expected.
You might be able to gain some insight into your trouble by looking at these two programs.
Here's the code for the master:
Code:
'****************************************************************
'* Name : SPI Master.pbp *
'* Author : Henrik Olsson *
'* Notice : Copyright (c) 2013 [Henrik Olsson] *
'* : All Rights Reserved *
'* Date : 2013-11-12 *
'* Version : 1.0 *
'* Notes : Designed to run on 18F45K20, AMICUS18 platform. *
'* : *
'****************************************************************
DEFINE OSC 64 ' Default oscillator speed on the AMICUS18 is 16*4MHz
DEFINE LOADER_USED 1 ' We're using a bootloader.
DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_CLROERR 1 ' Clear overflow automatically
DEFINE HSER_SPBRG 138 ' 115200 Baud @ 64MHz, -0,08%
SPBRGH = 0
BAUDCON.3 = 1 ' Enable 16 bit baudrate generator
TRISC = %10010110 ' RX, TX, SDO, SDI, SCK, N/U, N/U, CS
TRISB = %11111111 ' N/U, N/U, N/U, N/U, N/U, N/U, N/U, N/U
' Aliases for the MSSP module status and control bits.
SSPEN VAR SSPCON1.5 ' SSP Enable bit
CKP VAR SSPCON1.4 ' Clock Polarity Select
SMP VAR SSPSTAT.7 ' Data input sample phase
CKE VAR SSPSTAT.6 ' Clock Edge Select bit
BF VAR SSPSTAT.0 ' Buffer full flag.
' Set up the MSSP module.
CKP = 0 ' Clock idles low
CKE = 0 ' Transmit on idle to active transition.
SMP = 0 ' Sample in middle of data
SSPEN = 1 ' Enable SPI pins
SSPCON1.0 = 1 ' Slow down SPI clock to Fosc/16 for now.
i VAR BYTE
Response VAR BYTE
Response = SSPBUF ' Dummy read to buffer and BF-flag
HSEROUT ["Master start...", 13]
HSEROUT ["TX - RX",13]
Pause 5000
Main:
For i = "A" to "Z" ' Send letters A to Z
SSPBUF = i ' Load buffer with content
While BF = 0 : WEND ' Wait for operation to complete
Response = SSPBUF ' Read response
HSEROUT [i, " - ", Response, 13]
PAUSE 10
NEXT
HSEROUT ["Done.....", 13]
Pause 5000
Goto Main
And here's the code for the slave:
Code:
'****************************************************************
'* Name : SPI Slave.pbp *
'* Author : Henrik Olsson *
'* Notice : Copyright (c) 2013 [Henrik Olsson] *
'* : All Rights Reserved *
'* Date : 2013-11-12 *
'* Version : 1.0 *
'* Notes : Designed to run on 18F45K20, AMICUS18 platform. *
'* : *
'****************************************************************
DEFINE OSC 64 ' Default oscillator speed on the AMICUS18 is 16*4MHz
DEFINE LOADER_USED 1 ' We're using a bootloader.
DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_CLROERR 1 ' Clear overflow automatically
DEFINE HSER_SPBRG 138 ' 115200 Baud @ 64MHz, -0,08%
SPBRGH = 0
BAUDCON.3 = 1 ' Enable 16 bit baudrate generator
TRISC = %10011111 ' RX, TX, SDO, SDI, SCK, N/U, N/U, CS
TRISB = %11111111 ' N/U, N/U, N/U, N/U, N/U, N/U, N/U, N/U
' Aliases for the MSSP module status and control bits.
SSPEN VAR SSPCON1.5 ' SSP Enable bit
CKP VAR SSPCON1.4 ' Clock Polarity Select
SMP VAR SSPSTAT.7 ' Data input sample phase
CKE VAR SSPSTAT.6 ' Clock Edge Select bit
BF VAR SSPSTAT.0 ' Buffer Full bit
' Set up the MSSP module.
CKP = 0 ' Clock idles low
CKE = 0 ' Transmit on idle to active transition.
SMP = 0 ' Sample in middle of data
While PortC.4 = 1 : WEND ' Wait for SCK pin to be idle before enabling MSSP
SSPCON1 = %00100101 ' Slave mode, no SS
i VAR BYTE
Response VAR BYTE
HSEROUT ["Slave start...", 13]
HSEROUT ["RX - TX", 13]
Main:
For i = "Z" to "A" STEP -1
SSPBUF = i ' Load buffer
While BF = 0 : WEND ' Wait for data to arrive
Response = SSPBUF ' Read data from buffer, clears flag.
HSEROUT [Response, " - ", i, 13]
NEXT
HSEROUT ["Done...",13]
Goto Main
/Henrik.
Using SPI hardware
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