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iPod Nano2G: add IPOD_ACCESSORY_PROTOCOL

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Change-Id: I78a19972624504bc802d96b9b8e9cec132164c2c
This commit is contained in:
Cástor Muñoz 2016-05-14 14:24:49 +02:00
parent 60fb707203
commit 9a4cd2eaee
5 changed files with 183 additions and 20 deletions
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113
firmware/target/arm/s5l8700/ipodnano2g/serial-nano2g.c
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@ -47,6 +47,9 @@
extern const struct uartc s5l8701_uartc0;
#ifdef IPOD_ACCESSORY_PROTOCOL
void iap_rx_isr(int, char*, char*, uint32_t);
#endif
struct uartc_port ser_port IDATA_ATTR =
{
@ -61,7 +64,11 @@ struct uartc_port ser_port IDATA_ATTR =
.clkhz = NANO2G_UART_CLK_HZ,
/* interrupt callbacks */
#ifdef IPOD_ACCESSORY_PROTOCOL
.rx_cb = iap_rx_isr,
#else
.rx_cb = NULL,
#endif
.tx_cb = NULL, /* polling */
};
@ -94,3 +101,109 @@ void tx_writec(unsigned char c)
{
uartc_port_tx_byte(&ser_port, c);
}
#ifdef IPOD_ACCESSORY_PROTOCOL
#include "iap.h"
static enum {
ABR_STATUS_LAUNCHED, /* ST_SYNC */
ABR_STATUS_SYNCING, /* ST_SOF */
ABR_STATUS_DONE
} abr_status;
void serial_bitrate(int rate)
{
logf("[%lu] serial_bitrate(%d)", (uint32_t)USEC_TIMER, rate);
if (rate == 0) {
/* Using auto-bitrate (ABR) to detect accessory Tx speed:
*
* + Here:
* - Disable Rx logic to clean the FIFO and the shift
* register, thus no Rx data interrupts are generated.
* - Launch ABR and wait for a low pulse in Rx line.
*
* + In ISR, when a low pulse is detected (ideally it is the
* start bit of 0xff):
* - Calculate and configure detected speed.
* - Enable Rx to verify that the next received data frame
* is 0x55 or 0xff:
* - If so, it's assumed bit rate is correctly detected,
* it will not be modified until speed is changed using
* RB options menu.
* - If not, reset iAP state machine and launch a new ABR.
*/
uartc_port_set_rx_mode(&ser_port, UCON_MODE_DISABLED);
uartc_port_abr_start(&ser_port);
abr_status = ABR_STATUS_LAUNCHED;
}
else {
uint32_t brdata;
if (rate == 57600) brdata = BRDATA_57600;
else if (rate == 38400) brdata = BRDATA_38400;
else if (rate == 19200) brdata = BRDATA_19200;
else brdata = BRDATA_9600;
uartc_port_abr_stop(&ser_port); /* abort ABR if already launched */
uartc_port_set_bitrate_raw(&ser_port, brdata);
uartc_port_set_rx_mode(&ser_port, UCON_MODE_INTREQ);
abr_status = ABR_STATUS_DONE;
}
}
void iap_rx_isr(int len, char *data, char *err, uint32_t abr_cnt)
{
/* ignore Rx errors, upper layer will discard bad packets */
(void) err;
static int sync_retry;
if (abr_status == ABR_STATUS_LAUNCHED) {
/* autobauding */
if (abr_cnt) {
#define BR2CNT(s) (NANO2G_UART_CLK_HZ / (unsigned)(s))
if (abr_cnt < BR2CNT(57600*1.1) || abr_cnt > BR2CNT(9600*0.9)) {
/* detected speed out of range, relaunch ABR */
uartc_port_abr_start(&ser_port);
return;
}
/* valid speed detected, select it */
uint32_t brdata;
if (abr_cnt < BR2CNT(48000)) brdata = BRDATA_57600;
else if (abr_cnt < BR2CNT(33600)) brdata = BRDATA_38400;
else if (abr_cnt < BR2CNT(24000)) brdata = BRDATA_28800;
else if (abr_cnt < BR2CNT(14400)) brdata = BRDATA_19200;
else brdata = BRDATA_9600;
/* set detected speed */
uartc_port_set_bitrate_raw(&ser_port, brdata);
uartc_port_set_rx_mode(&ser_port, UCON_MODE_INTREQ);
/* enter SOF state */
iap_getc(0xff);
abr_status = ABR_STATUS_SYNCING;
sync_retry = 2; /* we are expecting [0xff] 0x55 */
}
}
/* process received data */
while (len--)
{
bool sync_done = !iap_getc(*data++);
if (abr_status == ABR_STATUS_SYNCING)
{
if (sync_done) {
abr_status = ABR_STATUS_DONE;
}
else if (--sync_retry == 0) {
/* invalid speed detected, relaunch ABR
discarding remaining data (if any) */
serial_bitrate(0);
break;
}
}
}
}
#endif /* IPOD_ACCESSORY_PROTOCOL */